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Bump MAX_CALL_FRAMES from 8 to 16 to allow deeper call chains
that Rust-BPF requires and update selftests.
Link: https://lore.kernel.org/r/20260613180755.29671-1-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Adding bpf_trampoline_multi_attach/detach functions that allows to
attach/detach tracing program to multiple functions/trampolines.
The attachment is defined with bpf_program and array of BTF ids of
functions to attach the bpf program to.
Adding bpf_tracing_multi_link object that holds all the attached
trampolines and is initialized in attach and used in detach.
The attachment allocates or uses currently existing trampoline
for each function to attach and links it with the bpf program.
The attach works as follows:
- we get all the needed trampolines
- lock them and add the bpf program to each (__bpf_trampoline_link_prog)
- the trampoline_multi_ops passed in __bpf_trampoline_link_prog gathers
ftrace_hash (ip -> trampoline) objects
- we call update_ftrace_direct_add/mod to update needed locations
- we unlock all the trampolines
The detach works as follows:
- we lock all the needed trampolines
- remove the program from each (__bpf_trampoline_unlink_prog)
- the trampoline_multi_ops passed in __bpf_trampoline_unlink_prog gathers
ftrace_hash (ip -> trampoline) objects
- we call update_ftrace_direct_del/mod to update needed locations
- we unlock and put all the trampolines
We store the old image/flags in the trampoline before the update
and use it in case we need to rollback the attachment.
We keep the ftrace_hash objects allocated during attach in the link
so they can be used for detach as well.
Adding trampoline_(un)lock_all functions to (un)lock all trampolines
to gate the tracing_multi attachment.
Note this is supported only for archs (x86_64) with ftrace direct and
have single ops support.
CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS &&
CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
It also needs CONFIG_BPF_SYSCALL enabled.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-13-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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The macro requires callers to pass a stack variable, but not all
callbacks use it. Add (void)__stack to suppress the clang W=1 warning.
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260602175204.624401-1-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Introduce release_reg() to consolidate the release logic shared by both
helpers and kfuncs: dynptr release, kptr_xchg percpu-to-RCU conversion,
regular reference release, and NULL pass-through. NULL pass-through is
only allowed if the prototype indicates the argument may be null.
Determine release_regno from the function prototype/metadata before
argument checking, rather than discovering it dynamically during
argument processing. For helpers, scan the arg_type array in
check_func_proto() via check_proto_release_reg(). For kfuncs, set
release_regno to BPF_REG_1 in bpf_fetch_kfunc_arg_meta() when
KF_RELEASE is set. In the future when we start adding decl_tag to
kfunc arguments, we can just look at the function prototype instead
of a release_regno.
Extract ref_convert_alloc_rcu_protected() and
invalidate_rcu_protected_refs() to make it more clear what the code is
doing. For ref_convert_alloc_rcu_protected(), it pre-converts
MEM_ALLOC | MEM_PERCPU registers to MEM_RCU (clearing id so they
survive), then calls release_reference() to invalidate the remaining
registers and release the reference state.
Add KF_RELEASE to bpf_dynptr_file_discard() so its release_regno is set
via fetch_kfunc_meta rather than being assigned manually in the dynptr
argument processing. Set arg_type to ARG_PTR_TO_DYNPTR for
KF_ARG_PTR_TO_DYNPTR so that check_func_arg_reg_off() correctly allows
non-zero stack offsets for dynptr release arguments same as helper.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-9-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Helpers and kfuncs independently tracked referenced object metadata
using standalone id fields in their respective arg_meta structs.
This led to duplicated logic and inconsistent error handling between the
two paths.
Introduce struct ref_obj_desc to consolidate id and parent_id along with
a count of how many arguments carry a reference. Add update_ref_obj() to
populate it from a bpf_reg_state, replacing open-coded assignments in
check_func_arg(), check_kfunc_args(), and process_iter_arg(). Add
validate_ref_obj() to check for ambiguous ref_obj before using it.
For ref_obj releasing helpers and kfuncs, keep checking it before
calling update_ref_obj() for now. A later patch will make these
functions not depending on ref_obj. For other users of ref_obj, move the
checks to the use locations. For helper, this means moving the checks
inside helper_multiple_ref_obj_use() to use locations.
is_acquire_function() is dropped as ref_obj is never used.
Pass ref_obj_desc into process_dynptr_func()/mark_stack_slots_dynptr()
instead of a bare parent_id to make it less confusing.
Drop the selftest introduced in 7ec899ac90a2 ("selftests/bpf: Negative
test case for ref_obj_id in args") since the verifier no longer
complains about ambiguous ref_obj if it is not used.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-8-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Refactor object relationship tracking in the verifier and fix a dynptr
use-after-free bug where file/skb dynptrs are not invalidated when the
parent referenced object is freed.
Add parent_id to bpf_reg_state to precisely track child-parent
relationships. A child object's parent_id points to the parent object's
id. This replaces the PTR_TO_MEM-specific dynptr_id.
Remove ref_obj_id from bpf_reg_state by folding its role into the
existing id field. Previously, id tracked pointer identity for null
checking while ref_obj_id tracked the owning reference for lifetime
management. These are now unified: acquire helpers and kfuncs set id
to the acquired reference id, and release paths use id directly.
Add reg_is_referenced() which checks if a register is referenced by
looking up its id in the reference array. This replaces all former
ref_obj_id checks.
For release_reference(), invalidating an object now also invalidates
all descendants by traversing the object tree. This is done using
stack-based DFS to avoid recursive call chains of release_reference() ->
unmark_stack_slots_dynptr() -> release_reference(). Referenced objects
encountered during tree traversal are reported as leaked references.
Add parent_id to bpf_reference_state to enable hierarchical reference
tracking. When acquiring a reference, a parent_id can be specified to
link the new reference to an existing one (e.g., referenced dynptrs
acquire a reference with parent_id linking to the parent object's
reference).
Pointer casting:
For pointer casting helpers (bpf_sk_fullsock, bpf_tcp_sock), instead of
propagating ref_obj_id, the cast result reuses the same reference id as
the source pointer. Since the cast may return NULL for a non-NULL input,
the NULL case is explored as a separate verifier branch. This allows
releasing any of the original or cast pointers to invalidate all others.
Referenced dynptrs:
When constructing a referenced dynptr, acquire a intermediate reference
with parent_id linking to the parent referenced object. The dynptr and
all clones share the same parent_id (pointing to the intermediate ref)
but get unique ids for independent slice tracking. Releasing a
referenced dynptr releases the parent reference, which in turn
invalidates all clones and their derived slices.
Owning to non-owning reference conversion:
After converting owning to non-owning by clearing id (e.g.,
object(id=1) -> object(id=0)), the verifier releases the reference
state via release_reference_nomark().
Note that the error message "reference has not been acquired before" in
the helper and kfunc release paths is removed. This message was already
unreachable. The verifier only calls release_reference() after
confirming the reference is valid, so the condition could never trigger
in practice.
Fixes: 870c28588afa ("bpf: net_sched: Add basic bpf qdisc kfuncs")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-6-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Simplify dynptr checking for helper and kfunc by unifying it. Remember
the initialized dynptr (i.e.,g !(arg_type |= MEM_UNINIT)) pass to a
dynptr kfunc during process_dynptr_func() so that we can easily
retrieve the information for verification later. By saving it in
meta->dynptr, there is no need to call dynptr helpers such as
dynptr_id(), dynptr_ref_obj_id() and dynptr_type() in check_func_arg().
Remove and open code the helpers in process_dynptr_func() when
saving id, ref_obj_id, and type.
Besides, since dynptr ref_obj_id information is now pass around in
meta->bpf_dynptr_desc, drop the check in helper_multiple_ref_obj_use.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-3-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Cross-merge BPF and other fixes after downstream PR.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Global subprogs are verified independently and are not descended into
when their callers are symbolically executed. This means a caller can
hold references or locks across a global subprog call that may throw,
while the verifier only checks the non-exceptional return path at the
call site.
Record whether a subprog might throw in the CFG summary pass, alongside
the existing might_sleep and packet-data-changing summaries, and
propagate that effect through reachable callees.
When a global subprog is marked as possibly throwing, push the normal
continuation and validate the exceptional path immediately at the call
site, avoiding a synthetic exception state and associated special case
in the pruning checks.
Fixes: f18b03fabaa9 ("bpf: Implement BPF exceptions")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260517075530.3461166-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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We've hit the 512 bytes limit on stack depth a few times in Cilium
recently. As a result, we started reporting in CI our current maximum
stack depth across all configurations for each BPF program.
Unfortunately, that is not trivial to compute in userspace. The
verifier reports the stack depths of individual subprogs at the end of
the logs. However the maximum combined stack depth also depends on the
callgraph of those subprogs (the max combined stack depth is the height
of the callgraph weighted by per-subprog stack depths). We can compute
a callgraph in userspace from the loaded instructions, but it often
doesn't match the verifier's own callgraph because of dead code
elimination. Our current approach relies on dumping the BPF_LOG_LEVEL2
logs, but this feels overkill considering the verifier already has the
information we need.
The patch lets the verifier dump the maximum combined stack depth in
the logs, on the same line as the per-subprog stack depths:
stack depth 16+256 max 272
The per-subprog stack depths and the new max stack depth are not
directly comparable. The former is sometimes updated during fixups,
while the latter is not. As a result, even with a single subprog, we
may end up with two slightly different values. The aim of the new max
value is to be closest to what is actually enforced by the verifier.
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/d3d23a0410f87f116f3bbaa98a815dbae113bda2.1778700777.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Extend the precision marking and backtracking infrastructure to
support stack argument slots (r11-based accesses). Without this,
precision demands for scalar values passed through stack arguments
are silently dropped, which could allow the verifier to incorrectly
prune states with different constant values in stack arg slots.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045025.2387526-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Move stack slot index (spi) and frame number out of the flags field
in bpf_jmp_history_entry into dedicated bitfields. This simplifies
the encoding and makes room for new flags.
Previously, spi and frame were packed into the lower 9 bits of the
12-bit flags field (3 bits frame + 6 bits spi), with INSN_F_STACK_ACCESS
at BIT(9) and INSN_F_DST/SRC_REG_STACK at BIT(10)/BIT(11).
But this has no room for an INSN_F_* flag for stack arguments.
To resolve this issue, bpf_jmp_history_entry field idx is narrowed to
20 bits (sufficient for insn indices up to 1M), and the freed bits hold
spi (6 bits) and frame (3 bits) as dedicated struct fields. The flags
enum is simplified accordingly:
INSN_F_STACK_ACCESS -> BIT(0)
INSN_F_DST_REG_STACK -> BIT(1)
INSN_F_SRC_REG_STACK -> BIT(2)
which allows more room for additional INSN_F_* flags.
bpf_push_jmp_history() now takes explicit spi and frame parameters
instead of encoding them into flags. The insn_stack_access_flags(),
insn_stack_access_spi(), and insn_stack_access_frameno() helpers are
removed.
No functional change.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045020.2385962-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Currently BPF functions (subprogs) are limited to 5 register arguments.
With [1], the compiler can emit code that passes additional arguments
via a dedicated stack area through bpf register BPF_REG_PARAMS (r11),
introduced in an earlier patch ([2]).
The compiler uses positive r11 offsets for incoming (callee-side) args
and negative r11 offsets for outgoing (caller-side) args, following the
x86_64/arm64 calling convention direction. There is an 8-byte gap at
offset 0 separating two regions:
Incoming (callee reads): r11+8 (arg6), r11+16 (arg7), ...
Outgoing (caller writes): r11-8 (arg6), r11-16 (arg7), ...
The following is an example to show how stack arguments are saved
and transferred between caller and callee:
int foo(int a1, int a2, int a3, int a4, int a5, int a6, int a7) {
...
bar(a1, a2, a3, a4, a5, a6, a7, a8);
...
}
Caller (foo) Callee (bar)
============ ============
Incoming (positive offsets): Incoming (positive offsets):
r11+8: [incoming arg 6] r11+8: [incoming arg 6] <-+
r11+16: [incoming arg 7] r11+16: [incoming arg 7] <-|+
r11+24: [incoming arg 8] <-||+
Outgoing (negative offsets): |||
r11-8: [outgoing arg 6 to bar] -------->-------------------------+||
r11-16: [outgoing arg 7 to bar] -------->--------------------------+|
r11-24: [outgoing arg 8 to bar] -------->---------------------------+
If the bpf function has more than one call:
int foo(int a1, int a2, int a3, int a4, int a5, int a6, int a7) {
...
bar1(a1, a2, a3, a4, a5, a6, a7, a8);
...
bar2(a1, a2, a3, a4, a5, a6, a7, a8, a9);
...
}
Caller (foo) Callee (bar2)
============ ==============
Incoming (positive offsets): Incoming (positive offsets):
r11+8: [incoming arg 6] r11+8: [incoming arg 6] <+
r11+16: [incoming arg 7] r11+16: [incoming arg 7] <|+
r11+24: [incoming arg 8] <||+
Outgoing for bar2 (negative offsets): r11+32: [incoming arg 9] <|||+
r11-8: [outgoing arg 6] ---->----------->-------------------------+|||
r11-16: [outgoing arg 7] ---->----------->--------------------------+||
r11-24: [outgoing arg 8] ---->----------->---------------------------+|
r11-32: [outgoing arg 9] ---->----------->----------------------------+
The verifier tracks outgoing stack arguments in stack_arg_regs[] and
out_stack_arg_cnt in bpf_func_state, separately from the regular
r10 stack. The callee does not copy incoming args — it reads them
directly from the caller's outgoing slots at positive r11 offsets.
Similar to stacksafe(), introduce stack_arg_safe() to do pruning
check.
Outgoing stack arg slots are invalidated when the callee returns
(e.g. in prepare_func_exit), not at call time. This allows the callee to
read incoming args from the caller's outgoing slots during
verification. The following are a few examples.
Example 1:
*(u64 *)(r11 - 8) = r6;
*(u64 *)(r11 - 16) = r7;
call bar1; // arg6 = r6, arg7 = r7
call bar2; // expected with 2 stack arguments, failed
Example 2:
To fix the Example 1:
*(u64 *)(r11 - 8) = r6;
*(u64 *)(r11 - 16) = r7;
call bar1; // arg6 = r6, arg7 = r7
*(u64 *)(r11 - 8) = r8;
*(u64 *)(r11 - 16) = r9;
call bar2; // arg6 = r8, arg7 = r9
Example 3:
The compiler can hoist the shared stack arg stores above the branch:
*(u64 *)(r11 - 16) = r7;
if cond goto else;
*(u64 *)(r11 - 8) = r8;
call bar1; // arg6 = r8, arg7 = r7
goto end;
else:
*(u64 *)(r11 - 8) = r9;
call bar2; // arg6 = r9, arg7 = r7
end:
Example 4:
Within a loop:
loop:
*(u64 *)(r11 - 8) = r6; // arg6, before loop
call bar; // reuses arg6 each iteration
if ... goto loop;
A separate max_out_stack_arg_cnt field in bpf_subprog_info tracks
the deepest outgoing slot actually written. This intends to
reject programs that write to slots beyond what any callee expects.
It is necessary for JIT.
Similar to typical compiler generated code, enforce the following
orderings:
- all stack arg reads must be ahead of any stack arg write
- all stack arg reads must be before any bpf func, kfunc and helpers
This is needed as JIT may emit 'mov' insns for read/write with
the same register and bpf function, kfunc and helper will invalidate
all arguments immediately after the call.
Callback functions with stack arguments need kernel setup parameter
types (including stack parameters) properly and then callback function
can retrieve such information for verification purpose.
Global subprogs and freplace with >5 args are not yet supported.
[1] https://github.com/llvm/llvm-project/pull/189060
[2] https://lore.kernel.org/bpf/20260423033506.2542005-1-yonghong.song@linux.dev/
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045015.2385013-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Convert the bpf_get_spilled_reg() macro to a static inline function
for better type safety and readability. This also simplifies the macro
definition in preparation for upcoming stack argument support which
will introduce additional macros.
No functional change.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513044954.2382693-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Many BPF_MAP_CREATE validation failures currently return -EINVAL without
any explanation to userspace.
Plumb common syscall log attributes into map_create(), create a verifier
log from bpf_common_attr::log_buf/log_size/log_level, and report
map-creation failure reasons through that buffer.
This improves debuggability by allowing userspace to inspect why map
creation failed and read back log_true_size from common attributes.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-7-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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BPF_PROG_LOAD can now take log parameters from both union bpf_attr and
struct bpf_common_attr. The merge rules are:
- if both sides provide a complete log tuple (buf/size/level) and they
match, use it;
- if only one side provides log parameters, use that one;
- if both sides provide complete tuples but they differ, return -EINVAL.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-5-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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The next commit will add support for reporting logs via extended common
attributes, including 'log_true_size'.
To prepare for that, refactor the 'log_true_size' reporting logic by
introducing a new struct bpf_log_attr to encapsulate log-related behavior:
* bpf_log_attr_init(): initialize log fields, which will support
extended common attributes in the next commit.
* bpf_log_attr_finalize(): handle log finalization and write back
'log_true_size' to userspace.
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260512153157.28382-4-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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When using global functions (i.e. subprogs), the verifier performs
function-by-function verification. In that case, the sum of the
instructions processed in each global function and in the main program
counts towards the 1 million instructions limit. Only that sum is
reported in the verifier logs.
While starting to use global functions in Cilium (finally!), we found it
can be useful to have the breakdown per global function, to understand
exactly where the budget is currently spent. This patch implements this
breakdown, under BPF_LOG_STATS, as done for the stack depths.
When iterating over subprogs, we need to skip the hidden subprogs at the
end because they don't have a corresponding func_info_aux entry and
calling bpf_subprog_is_global() would result in an OOB access.
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/bpf/5590f9c67e614ec9054d0c7e74e87cc690a52c56.1777538384.git.paul.chaignon@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
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Replace eight independent s64, u64, s32, u32 min/max fields in
bpf_reg_state with two circular number fields:
- cnum64 for a unified signed/unsigned 64-bit range tracking;
- cnum32 for a unified signed/unsigned 32-bit range tracking.
Each cnum represents a range as a single arc on the circular number
line (base + size), from which signed and unsigned bounds are derived
on demand via accessor functions introduced in the preceding commit.
Notable changes:
- Signed<->unsigned deductions in __reg_deduce_bounds() are removed.
- 64<->32 bit deductions are replaced with:
- reg->r32 = cnum32_intersect(reg->r32, cnum32_from_cnum64(reg->r64));
this is functionally equivalent to the old code.
- reg->r64 = cnum64_cnum32_intersect(reg->r64, reg->r32);
this handles a few additional cases, see commit message for
"bpf: representation and basic operations on circular numbers".
- regs_refine_cond_op() now computes results in terms of operations on
sets, e.g. for JNE:
/* Complement of the range [val, val] as cnum64. */
lo = (struct cnum64){ val + 1, U64_MAX - 1 };
reg1->r64 = cnum64_intersect(reg1->r64, lo);
- For add, sub operations on scalars replace explicit bounds
computations with cnum{32,64}_{add,negate}.
- For add, sub operations on pointers deduplicate with arithmetic
operations on scalars and use cnum{32,64}_{add,negate}.
- For and, or, xor operations on scalars remove explicit signed bounds
computations.
- range_bounds_violation() reduces to checking cnum_is_empty().
- const_tnum_range_mismatch() reduces to checking cnum_is_const().
Selftest adjustments: a few existing tests are updated because a
single cnum arc cannot always represent what the old system expressed
as the intersection of independent signed and unsigned ranges.
For example, if the old system tracked u64=[0, U64_MAX-U32_MAX+2] and
s64=[S64_MIN+2, 2] independently, their intersection is a tight
two-point set. A single cnum must pick the shorter arc, losing the
other constraint. These cases are documented with comments in the
adjusted tests.
reg_bounds.c is updated with logic similar to
cnum64_cnum32_intersect(). Instead of using cnums it inspects
intersection between 'b' and first / last / next-after-first /
previous-before-last sub-ranges of 'a'.
reg_bounds.c is also updated to skip test cases that rely
in signed and unsigned ranges intersecting in two intervals,
as such cases are not representable by a single cnum.
The following "crafted" test cases are affected:
- reg_bounds_crafted/(s64)[0xffffffffffff8000; 0x7fff] (u32)<op> [0; 0x1f]
- reg_bounds_crafted/(s64)[0; 0x1f] (u32)<op> [0xffffffffffffff80; 0x7f]
- reg_bounds_crafted/(s64)[0xffffffffffffff80; 0x7f] (u32)<op> [0; 0x1f]
- reg_bounds_crafted/(u64)[0; 1] (s32)<op> [1; 2147483648]
- reg_bounds_crafted/(u64)[1; 2147483648] (s32)<op> [0; 1]
- reg_bounds_crafted/(u64)[0; 0xffffffff00000000] (s64)<op> 0
- reg_bounds_crafted/(u64)0 (s64)<op> [0; 0xffffffff00000000]
- reg_bounds_crafted/(u64)[0; 0xffffffff00000000] (s32)<op> 0
- reg_bounds_crafted/(u64)0 (s32)<op> [0; 0xffffffff00000000]
- reg_bounds_crafted/(s64)[S64_MIN; 0] (u64)<op> S64_MIN
- reg_bounds_crafted/(s64)S64_MIN (u64)<op> [S64_MIN; 0]
- reg_bounds_crafted/(s32)[S32_MIN; 0] (u32)<op> S32_MIN
- reg_bounds_crafted/(s32)S32_MIN (u32)<op> [S32_MIN; 0]
- reg_bounds_crafted/(s64)[0; 0x1f] (u32)<op> [0xffffffff80000000; 0x7fffffff]
- reg_bounds_crafted/(s64)[0xffffffff80000000; 0x7fffffff] (u32)<op> [0; 0x1f]
- reg_bounds_crafted/(s64)[0; 0x1f] (u32)<op> [0xffffffffffff8000; 0x7fff]
As well as some reg_bounds_roand_{consts,ranges}_A_B, where A and B
differ in sign domain.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260424-cnums-everywhere-rfc-v1-v3-3-ca434b39a486@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Replace direct access to bpf_reg_state->{smin,smax,umin,umax,
s32_min,s32_max,u32_min,u32_max}_value with getter/setter inline
functions, preparing for future switch to cnum-based internal
representation.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260424-cnums-everywhere-rfc-v1-v3-2-ca434b39a486@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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This change prepares verifier log reporting for upcoming kfunc stack
argument support.
Currently verifier log code mostly assumes that an argument can be
described directly by a register number. That works for arguments
passed in `R1` to `R5`, but it does not work once kfunc arguments
can also be passed on the stack.
Introduce an opaque `argno_t` type that encodes both register-based
and arg-based references. Four helpers form the interface:
- argno_from_reg(regno): create from a register number
- argno_from_arg(arg): create from a 1-based arg number
- reg_from_argno(a): extract register number, or -1
- arg_from_argno(a): extract arg number, or -1
reg_arg_name() converts an argno_t to a human-readable string for
verifier logs: "R%d" for register arguments, or "*(R11-off)" for
stack arguments beyond R5.
Update selftests accordingly.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260423033501.2539667-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Introduce helper bpf_insn_is_indirect_target to check whether a BPF
instruction is an indirect jump target.
Since the verifier knows which instructions are indirect jump targets,
add a new flag indirect_target to struct bpf_insn_aux_data to mark
them. The verifier sets this flag when verifying an indirect jump target
instruction, and the helper checks the flag to determine whether an
instruction is an indirect jump target.
Reviewed-by: Anton Protopopov <a.s.protopopov@gmail.com> #v8
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> #v12
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20260416064341.151802-4-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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BTF validation logic is independent from the main verifier.
Move it into check_btf.c
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260412152936.54262-7-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Move precision propagation and backtracking logic to backtrack.c
to reduce verifier.c size.
No functional changes.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260412152936.54262-6-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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verifier.c is huge. Move is_state_visited() to states.c,
so that all state equivalence logic is in one file.
Mechanical move. No functional changes.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260412152936.54262-5-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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verifier.c is huge. Move check_cfg(), compute_postorder(),
compute_scc() into cfg.c
Mechanical move. No functional changes.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260412152936.54262-4-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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verifier.c is huge. Move compute_insn_live_regs() into liveness.c.
Mechanical move. No functional changes.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260412152936.54262-3-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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verifier.c is huge. Split fixup/post-processing logic that runs after
the verifier accepted the program into fixups.c.
Mechanical move. No functional changes.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260412152936.54262-2-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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As a sanity check poison stack slots that stack liveness determined
to be dead, so that any read from such slots will cause program rejection.
If stack liveness logic is incorrect the poison can cause
valid program to be rejected, but it also will prevent unsafe program
to be accepted.
Allow global subprogs "read" poisoned stack slots.
The static stack liveness determined that subprog doesn't read certain
stack slots, but sizeof(arg_type) based global subprog validation
isn't accurate enough to know which slots will actually be read by
the callee, so it needs to check full sizeof(arg_type) at the caller.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-14-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Instead of breadcrumbs like:
(d2,cs15) frame 0 insn 18 +live -16
(d2,cs15) frame 0 insn 17 +live -16
Print final accumulated stack use/def data per-func_instance
per-instruction. printed func_instance's are ordered by callsite and
depth. For example:
stack use/def subprog#0 shared_instance_must_write_overwrite (d0,cs0):
0: (b7) r1 = 1
1: (7b) *(u64 *)(r10 -8) = r1 ; def: fp0-8
2: (7b) *(u64 *)(r10 -16) = r1 ; def: fp0-16
3: (bf) r1 = r10
4: (07) r1 += -8
5: (bf) r2 = r10
6: (07) r2 += -16
7: (85) call pc+7 ; use: fp0-8 fp0-16
8: (bf) r1 = r10
9: (07) r1 += -16
10: (bf) r2 = r10
11: (07) r2 += -8
12: (85) call pc+2 ; use: fp0-8 fp0-16
13: (b7) r0 = 0
14: (95) exit
stack use/def subprog#1 forwarding_rw (d1,cs7):
15: (85) call pc+1 ; use: fp0-8 fp0-16
16: (95) exit
stack use/def subprog#1 forwarding_rw (d1,cs12):
15: (85) call pc+1 ; use: fp0-8 fp0-16
16: (95) exit
stack use/def subprog#2 write_first_read_second (d2,cs15):
17: (7a) *(u64 *)(r1 +0) = 42
18: (79) r0 = *(u64 *)(r2 +0) ; use: fp0-8 fp0-16
19: (95) exit
For groups of three or more consecutive stack slots, abbreviate as
follows:
25: (85) call bpf_loop#181 ; use: fp2-8..-512 fp1-8..-512 fp0-8..-512
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-10-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Rework func_instance identification and remove the dynamic liveness
API, completing the transition to fully static stack liveness analysis.
Replace callchain-based func_instance keys with (callsite, depth)
pairs. The full callchain (all ancestor callsites) is no longer part
of the hash key; only the immediate callsite and the call depth
matter. This does not lose precision in practice and simplifies the
data structure significantly: struct callchain is removed entirely,
func_instance stores just callsite, depth.
Drop must_write_acc propagation. Previously, must_write marks were
accumulated across successors and propagated to the caller via
propagate_to_outer_instance(). Instead, callee entry liveness
(live_before at subprog start) is pulled directly back to the
caller's callsite in analyze_subprog() after each callee returns.
Since (callsite, depth) instances are shared across different call
chains that invoke the same subprog at the same depth, must_write
marks from one call may be stale for another. To handle this,
analyze_subprog() records into a fresh_instance() when the instance
was already visited (must_write_initialized), then merge_instances()
combines the results: may_read is unioned, must_write is intersected.
This ensures only slots written on ALL paths through all call sites
are marked as guaranteed writes.
This replaces commit_stack_write_marks() logic.
Skip recursive descent into callees that receive no FP-derived
arguments (has_fp_args() check). This is needed because global
subprogram calls can push depth beyond MAX_CALL_FRAMES (max depth
is 64 for global calls but only 8 frames are accommodated for FP
passing). It also handles the case where a callback subprog cannot be
determined by argument tracking: such callbacks will be processed by
analyze_subprog() at depth 0 independently.
Update lookup_instance() (used by is_live_before queries) to search
for the func_instance with maximal depth at the corresponding
callsite, walking depth downward from frameno to 0. This accounts for
the fact that instance depth no longer corresponds 1:1 to
bpf_verifier_state->curframe, since skipped non-FP calls create gaps.
Remove the dynamic public liveness API from verifier.c:
- bpf_mark_stack_{read,write}(), bpf_reset/commit_stack_write_marks()
- bpf_update_live_stack(), bpf_reset_live_stack_callchain()
- All call sites in check_stack_{read,write}_fixed_off(),
check_stack_range_initialized(), mark_stack_slot_obj_read(),
mark/unmark_stack_slots_{dynptr,iter,irq_flag}()
- The per-instruction write mark accumulation in do_check()
- The bpf_update_live_stack() call in prepare_func_exit()
mark_stack_read() and mark_stack_write() become static functions in
liveness.c, called only from the static analysis pass. The
func_instance->updated and must_write_dropped flags are removed.
Remove spis_single_slot(), spis_one_bit() helpers from bpf_verifier.h
as they are no longer used.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Tested-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-9-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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After arg tracking reaches a fixed point, perform a single linear scan
over the converged at_in[] state and translate each memory access into
liveness read/write masks on the func_instance:
- Load/store instructions: FP-derived pointer's frame and offset(s)
are converted to half-slot masks targeting
per_frame_masks->{may_read,must_write}
- Helper/kfunc calls: record_call_access() queries
bpf_helper_stack_access_bytes() / bpf_kfunc_stack_access_bytes()
for each FP-derived argument to determine access size and direction.
Unknown access size (S64_MIN) conservatively marks all slots from
fp_off to fp+0 as read.
- Imprecise pointers (frame == ARG_IMPRECISE): conservatively mark
all slots in every frame covered by the pointer's frame bitmask
as fully read.
- Static subprog calls with unresolved arguments: conservatively mark
all frames as fully read.
Instead of a call to clean_live_states(), start cleaning the current
state continuously as registers and stack become dead since the static
analysis provides complete liveness information. This makes
clean_live_states() and bpf_verifier_state->cleaned unnecessary.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-8-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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The analysis is a basis for static liveness tracking mechanism
introduced by the next two commits.
A forward fixed-point analysis that tracks which frame's FP each
register value is derived from, and at what byte offset. This is
needed because a callee can receive a pointer to its caller's stack
frame (e.g. r1 = fp-16 at the call site), then do *(u64 *)(r1 + 0)
inside the callee — a cross-frame stack access that the callee's local
liveness must attribute to the caller's stack.
Each register holds an arg_track value from a three-level lattice:
- Precise {frame=N, off=[o1,o2,...]} — known frame index and
up to 4 concrete byte offsets
- Offset-imprecise {frame=N, off_cnt=0} — known frame, unknown offset
- Fully-imprecise {frame=ARG_IMPRECISE, mask=bitmask} — unknown frame,
mask says which frames might be involved
At CFG merge points the lattice moves toward imprecision (same
frame+offset stays precise, same frame different offsets merges offset
sets or becomes offset-imprecise, different frames become
fully-imprecise with OR'd bitmask).
The analysis also tracks spills/fills to the callee's own stack
(at_stack_in/out), so FP derived values spilled and reloaded.
This pass is run recursively per call site: when subprog A calls B
with specific FP-derived arguments, B is re-analyzed with those entry
args. The recursion follows analyze_subprog -> compute_subprog_args ->
(for each call insn) -> analyze_subprog. Subprogs that receive no
FP-derived args are skipped during recursion and analyzed
independently at depth 0.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-7-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Convert liveness bitmask type from u64 to spis_t, doubling the number
of trackable stack slots from 64 to 128 to support 4-byte granularity.
Each 8-byte SPI now maps to two consecutive 4-byte sub-slots in the
bitmask: spi*2 half and spi*2+1 half. In verifier.c,
check_stack_write_fixed_off() now reports 4-byte aligned writes of
4-byte writes as half-slot marks and 8-byte aligned 8-byte writes as
two slots. Similar logic applied in check_stack_read_fixed_off().
Queries (is_live_before) are not yet migrated to half-slot
granularity.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-4-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Add helper functions for manipulating u64[2] bitmasks that represent
4-byte stack slot liveness. The 512-byte BPF stack is divided into
128 4-byte slots, requiring 128 bits (two u64s) to track.
These will be used by the static stack liveness analysis in the
next commit.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-3-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Subprogram name can be computed from function info and BTF, but it is
convenient to have the name readily available for logging purposes.
Update comment saying that bpf_subprog_info->start has to be the first
field, this is no longer true, relevant sites access .start field
by it's name.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-2-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Namely:
- bpf_subprog_is_global
- bpf_vlog_alignment
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260410-patch-set-v4-1-5d4eecb343db@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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The static stack liveness analysis needs to know how many bytes a
helper or kfunc accesses through a stack pointer argument, so it can
precisely mark the affected stack slots as stack 'def' or 'use'.
Add bpf_helper_stack_access_bytes() and bpf_kfunc_stack_access_bytes()
which resolve the access size for a given call argument.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260403024422.87231-7-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Move several helpers to header as preparation for
the subsequent stack liveness patches.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260403024422.87231-6-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Add two passes before the main verifier pass:
bpf_compute_const_regs() is a forward dataflow analysis that tracks
register values in R0-R9 across the program using fixed-point
iteration in reverse postorder. Each register is tracked with
a six-state lattice:
UNVISITED -> CONST(val) / MAP_PTR(map_index) /
MAP_VALUE(map_index, offset) / SUBPROG(num) -> UNKNOWN
At merge points, if two paths produce the same state and value for
a register, it stays; otherwise it becomes UNKNOWN.
The analysis handles:
- MOV, ADD, SUB, AND with immediate or register operands
- LD_IMM64 for plain constants, map FDs, map values, and subprogs
- LDX from read-only maps: constant-folds the load by reading the
map value directly via bpf_map_direct_read()
Results that fit in 32 bits are stored per-instruction in
insn_aux_data and bitmasks.
bpf_prune_dead_branches() uses the computed constants to evaluate
conditional branches. When both operands of a conditional jump are
known constants, the branch outcome is determined statically and the
instruction is rewritten to an unconditional jump.
The CFG postorder is then recomputed to reflect new control flow.
This eliminates dead edges so that subsequent liveness analysis
doesn't propagate through dead code.
Also add runtime sanity check to validate that precomputed
constants match the verifier's tracked state.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260403024422.87231-5-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Add a pass that sorts subprogs in topological order so that iterating
subprog_topo_order[] walks leaf subprogs first, then their callers.
This is computed as a DFS post-order traversal of the CFG.
The pass runs after check_cfg() to ensure the CFG has been validated
before traversing and after postorder has been computed to avoid
walking dead code.
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260403024422.87231-3-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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In a subsequent patch, the regs_refine_cond_op and reg_bounds_sync
functions will be called in is_branch_taken instead of reg_set_min_max,
to simulate each branch's outcome. Since they will run before we branch
out, these two functions will need to work on temporary registers for
the two branches.
This refactoring patch prepares for that change, by introducing the
temporary registers on bpf_verifier_env and using them in
reg_set_min_max.
This change also allows us to save one fake_reg slot as we don't need to
allocate an additional temporary buffer in case of a BPF_K condition.
Finally, you may notice that this patch removes the check for
"false_reg1 == false_reg2" in reg_set_min_max. That check was introduced
in commit d43ad9da8052 ("bpf: Skip bounds adjustment for conditional
jumps on same scalar register") to avoid an invariant violation. Given
that "env->false_reg1 == env->false_reg2" doesn't make sense and
invariant violations are addressed in a subsequent commit, this patch
just removes the check.
Suggested-by: Eduard Zingerman <eddyz87@gmail.com>
Co-developed-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/260b0270052944a420e1c56e6a92df4d43cadf03.1775142354.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Factor the return value range calculation logic in check_return_code
out of the function in preparation for separating the return value
validation logic for BPF_EXIT and bpf_throw().
No functional changes. The change made in return_retval_code's handling
of PROG_TRACING program types (not error'ing on the default case) is a
no-op because the match on the program attach type is exhaustive.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260228184759.108145-2-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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This field is now used only for linked scalar registers tracking.
Rename it to 'delta' to better describe it's purpose:
constant delta between "linked" scalars with the same ID.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260212-ptrs-off-migration-v2-4-00820e4d3438@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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This commit consolidates static and varying pointer offset tracking
logic. All offsets are now represented solely using `.var_off` and
min/max fields. The reasons are twofold:
- This simplifies pointer tracking code, as each relevant function
needs to check the `.var_off` field anyway.
- It makes it easier to widen pointer registers for the purpose of loop
convergence checks, by forgoing the `regsafe()` logic demanding
`.off` fields to be identical.
The changes are spread across many functions and are hard to group
into smaller patches. Some of the logical changes include:
- Checks in __check_ptr_off_reg() are reordered so that the
tnum_is_const() check is done before operating on reg->var_off.value.
- check_packet_access() now uses check_mem_region_access() to handle
possible 'off' overflow cases.
- In check_helper_mem_access() utility functions like
check_packet_access() are now called with 'off=0', as these utility
functions now account for the complete register offset range.
- In check_reg_type() a call to __check_ptr_off_reg() is added before
a call to btf_struct_ids_match(). This prevents
btf_struct_ids_match() from potentially working on non-constant
reg->var_off.value.
- regsafe() is relaxed to avoid comparing '.off' field for pointers.
As a precaution, the changes are verified in [1] by adding a pass
checking that no pointer has non-zero '.off' field on each
do_check_insn() iteration.
[1] https://github.com/eddyz87/bpf/tree/ptrs-off-migration
Notable selftests changes:
- `.var_off` value changed because it now combines static and varying
offsets. Affected tests:
- linked_list/incorrect_node_var_off
- linked_list/incorrect_head_var_off2
- verifier_align/packet_variable_offset
- Overflowing `smax_value` bound leads to a pointer with big negative
or positive offset to be rejected immediately (previously overflowing
`rX += const` instruction updated `.off` field avoiding the overflow).
Affected tests:
- verifier_align/dubious_pointer_arithmetic
- verifier_bounds/var_off_insn_off_test1
- Invalid access to packet now reports full offset inside a packet.
Affected tests:
- verifier_direct_packet_access/test23_x_pkt_ptr_4
- A change in check_mem_region_access() behavior:
when register `.smin_value` is negative, it reports
"rX min value is negative..." before calling into __check_mem_access()
which reports "invalid access to ...".
In the tests below, the `.off` field was negative, while `.smin_value`
remained positive. This is no longer the case after the changes in
this commit. Affected tests:
- verifier_gotox/jump_table_invalid_mem_acceess_neg
- verifier_helper_packet_access/test15_cls_helper_fail_sub
- verifier_helper_value_access/imm_out_of_bound_2
- verifier_helper_value_access/reg_out_of_bound_2
- verifier_meta_access/meta_access_test2
- verifier_value_ptr_arith/known_scalar_from_different_maps
- lower_oob_arith_test_1
- value_ptr_known_scalar_3
- access_value_ptr_known_scalar
- Usage of check_mem_region_access() instead of __check_mem_access()
in check_packet_access() changes the reported message from
"rX offset is outside ..." to "rX min/max value is outside ...".
Affected tests:
- verifier_xdp_direct_packet_access/*
- In check_func_arg_reg_off() the check for zero offset now operates
on `.var_off` field instead of `.off` field. For tests where the
pattern looks like `kfunc(reg_with_var_off, ...)`, this changes the
reported error:
- previously the error "variable ... access ... disallowed"
was reported by __check_ptr_off_reg();
- now "R1 must have zero offset ..." is reported by
check_func_arg_reg_off() itself.
Affected tests:
- verifier/calls.c
"calls: invalid kfunc call: PTR_TO_BTF_ID with variable offset"
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260212-ptrs-off-migration-v2-2-00820e4d3438@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Previously, the verifier only tracked positive constant deltas between
linked registers using BPF_ADD. This limitation meant patterns like:
r1 = r0;
r1 += -4;
if r1 s>= 0 goto l0_%=; // r1 >= 0 implies r0 >= 4
// verifier couldn't propagate bounds back to r0
if r0 != 0 goto l0_%=;
r0 /= 0; // Verifier thinks this is reachable
l0_%=:
Similar limitation exists for 32-bit registers.
With this change, the verifier can now track negative deltas in reg->off
enabling bound propagation for the above pattern.
For alu32, we make sure the destination register has the upper 32 bits
as 0s before creating the link. BPF_ADD_CONST is split into
BPF_ADD_CONST64 and BPF_ADD_CONST32, the latter is used in case of alu32
and sync_linked_regs uses this to zext the result if known_reg has this
flag.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260204151741.2678118-2-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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The verifier assigns ids to scalar registers/stack slots when they are
linked through a mov or stack spill/fill instruction. These ids are
later used to propagate newly found bounds from one register to all
registers that share the same id. The verifier also compares the ids of
these registers in current state and cached state when making pruning
decisions.
When an ID becomes singular (i.e., only a single register or stack slot
has that ID), it can no longer participate in bounds propagation. During
comparisons between current and cached states for pruning decisions,
however, such stale IDs can prevent pruning of otherwise equivalent
states.
Find and clear all singular ids before caching a state in
is_state_visited(). struct bpf_idset which is currently unused has been
repurposed for this use case.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260203165102.2302462-3-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Currently, reset_idmap_scratch() performs a 4.7KB memset() in every
states_equal() call. Optimize this by using a counter to track used
ID mappings, replacing the O(N) memset() with an O(1) reset and
bounding the search loop in check_ids().
Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20260120023234.77673-1-realwujing@gmail.com
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Currently, nested rcu critical sections are rejected by the verifier and
rcu_lock state is managed by a boolean variable. Add support for nested
rcu critical sections by make active_rcu_locks a counter similar to
active_preempt_locks. bpf_rcu_read_lock() increments this counter and
bpf_rcu_read_unlock() decrements it, MEM_RCU -> PTR_UNTRUSTED transition
happens when active_rcu_locks drops to 0.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251117200411.25563-2-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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This updates bpf_insn_successors() reflecting that control flow might
jump over the instructions between tail call and function exit, verifier
might assume that some writes to parent stack always happen, which is
not the case.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Martin Teichmann <martin.teichmann@xfel.eu>
Link: https://lore.kernel.org/r/20251119160355.1160932-4-martin.teichmann@xfel.eu
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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