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The bpf_map_elem iterator, for all but the per-cpu maps, and the
bpf_sk_storage_map iterator hand the live value of an element to the
program as a writable buffer. The verifier does not know the map when it
checks the program, so nothing keeps the program from writing over a
bpf_spin_lock, a bpf_timer, a kptr or another special field, which neither
a map update nor a pointer to a map value can touch. With CAP_BPF and
CAP_PERFMON, or a BPF token, a program can so make the kernel follow a
pointer of its choice: after a write over a bpf_timer the kernel crashes
on the written value when the element is removed.
Offsets into a buffer are constants. Let the verifier record the range of
bytes that a program may write through a read-write buffer, and refuse the
program with -EACCES, at attach and at a link update, if a special field
of the map lies in that range.
A program that only reads, or that writes beside the special fields, works
as before. One that writes on both sides of a special field is refused,
since the range covers the field.
Fixes: d6c4503cc296 ("bpf: Implement bpf iterator for hash maps")
Fixes: 5ce6e77c7edf ("bpf: Implement bpf iterator for sock local storage map")
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261017163745.3341787-30-alexei.starovoitov@gmail.com
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The bpf_map_elem, bpf_sk_storage_map and sockmap iterators hand the key
and the value of an element to the program as buffers. The verifier only
records how far a program reaches into them, and ->attach_target()
compares that with the key and value size of the map.
bpf_iter_link_replace() does not. BPF_LINK_UPDATE installs a program that
an attach refuses with -EACCES, and the program then reads, and for a
value writes, behind every element that the iterator visits. It takes
CAP_BPF and CAP_PERFMON, or a BPF token.
Split the test out of the three ->attach_target() and ask it, as
->check_prog(), for the new program of an update as well. Targets without
such a test take every program of their kind, as before.
Fixes: d6c4503cc296 ("bpf: Implement bpf iterator for hash maps")
Fixes: 5ce6e77c7edf ("bpf: Implement bpf iterator for sock local storage map")
Fixes: 0365351524d7 ("net: Allow iterating sockmap and sockhash")
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261017163745.3341787-20-alexei.starovoitov@gmail.com
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BPF programs that manage their own objects have no way to run their own
logic once an RCU grace period has elapsed. bpf_obj_drop() defers a
free, but returning an index to an allocator or unpinning a resource
once readers are done has no equivalent. sched_ext's BPF library works
around this today by pushing freed nodes onto a list and having a
userspace thread call membarrier(MEMBARRIER_CMD_GLOBAL) and then run a
BPF program to reclaim them.
Add:
int bpf_call_rcu(struct bpf_rcu_head *rh, void *map,
int (*callback)(struct bpf_map *map, void *key,
void *value));
@rh is a struct bpf_rcu_head embedded in a value of @map, so the
callback runs as callback(map, key, value) for the element it lives in
and needs no cookie. A head can only be armed once, which bounds
outstanding work by the number of elements.
struct bpf_rcu_head holds the callback state inline rather than a
pointer to it, as bpf_timer, bpf_wq and bpf_task_work do, because there
is nothing to cancel and so nothing that has to outlive the map value.
That avoids an allocation and a state machine on the arming path at the
cost of 48 bytes per element.
An RCU callback cannot be cancelled, so everything it touches has to
stay alive until it runs:
- The callback is the program's text, so arming takes a program
reference as bpf_timer, bpf_wq and bpf_task_work do, dropped once
the callback returns. bpf_prog_inc_not_zero() also fails the arm
with -EBADF once the program is dying.
- The map is held by that reference through used_maps. An inner map
is not, so bpf_rcu_head is rejected in one.
- The field is only accepted in BPF_MAP_TYPE_ARRAY, whose elements
are never freed individually. A hash element can be deleted and
recycled while a callback is queued on it.
- The head is disarmed before the callback runs so it can be armed
again from there, which takes a new program reference before the
running callback drops its own. Arming therefore fails with -EPERM
once the map is held by neither a process nor bpffs.
bpf_iter hands a program a writable pointer to the live element, which
would let it overwrite a queued head, so bpf_iter_attach_map() rejects
maps carrying one.
The callback is verified non-sleepable even when the caller is
sleepable, and RCU invokes it with BH disabled.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20260922200208.3203834-2-puranjay@kernel.org
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Implement get_next_key, batch lookup/lookup-and-delete, for_each_map_elem
callback, and the seq_file BPF iterator for BPF_MAP_TYPE_RHASH.
get_next_key() and batch use rhashtable_next_key() — stateless,
matches the syscall UAPI shape (no kernel-side iterator state).
get_next_key falls back to the first key when prev_key was
concurrently deleted (matches htab semantics). Batch reports
cursor loss as -EAGAIN so userspace can distinguish it from
end-of-iteration (-ENOENT) and restart from NULL.
The seq_file BPF iterator uses rhashtable_walk_* instead. It runs
only from read() syscall context, so the walker's spin_lock is
safe, and seq_file's per-fd state lets the walker handle rehash
correctly (retry on -EAGAIN) for stronger coverage than the
stateless API can provide.
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20260605-rhash-v7-5-5b8e05f8630d@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Exclusive maps (aka excl_prog_hash) are meant to be reachable only
from the single program whose hash matches. This is enforced by
check_map_prog_compatibility() when the map is referenced from a
program such as signed BPF loaders.
A bpf_map_elem iterator, however, binds its target map at attach
time in bpf_iter_attach_map() instead of referencing it from the
program, so the exclusivity check is never reached. On top of that,
the iterator exposes the map value as a writable buffer.
Fixes: baefdbdf6812 ("bpf: Implement exclusive map creation")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260602133052.423725-2-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Now that KF_TRUSTED_ARGS is the default for all kfuncs, remove the
explicit KF_TRUSTED_ARGS flag from all kfunc definitions and remove the
flag itself.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260102180038.2708325-3-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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This commit marks kfuncs as such inside the .BTF_ids section. The upshot
of these annotations is that we'll be able to automatically generate
kfunc prototypes for downstream users. The process is as follows:
1. In source, use BTF_KFUNCS_START/END macro pair to mark kfuncs
2. During build, pahole injects into BTF a "bpf_kfunc" BTF_DECL_TAG for
each function inside BTF_KFUNCS sets
3. At runtime, vmlinux or module BTF is made available in sysfs
4. At runtime, bpftool (or similar) can look at provided BTF and
generate appropriate prototypes for functions with "bpf_kfunc" tag
To ensure future kfunc are similarly tagged, we now also return error
inside kfunc registration for untagged kfuncs. For vmlinux kfuncs,
we also WARN(), as initcall machinery does not handle errors.
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Acked-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/e55150ceecbf0a5d961e608941165c0bee7bc943.1706491398.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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BPF kfuncs are meant to be called from BPF programs. Accordingly, most
kfuncs are not called from anywhere in the kernel, which the
-Wmissing-prototypes warning is unhappy about. We've peppered
__diag_ignore_all("-Wmissing-prototypes", ... everywhere kfuncs are
defined in the codebase to suppress this warning.
This patch adds two macros meant to bound one or many kfunc definitions.
All existing kfunc definitions which use these __diag calls to suppress
-Wmissing-prototypes are migrated to use the newly-introduced macros.
A new __diag_ignore_all - for "-Wmissing-declarations" - is added to the
__bpf_kfunc_start_defs macro based on feedback from Andrii on an earlier
version of this patch [0] and another recent mailing list thread [1].
In the future we might need to ignore different warnings or do other
kfunc-specific things. This change will make it easier to make such
modifications for all kfunc defs.
[0]: https://lore.kernel.org/bpf/CAEf4BzaE5dRWtK6RPLnjTW-MW9sx9K3Fn6uwqCTChK2Dcb1Xig@mail.gmail.com/
[1]: https://lore.kernel.org/bpf/ZT+2qCc%2FaXep0%2FLf@krava/
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20231031215625.2343848-1-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Register the bpf_map_sum_elem_count func for all programs, and update the
map_ptr subtest of the test_progs test to test the new functionality.
The usage is allowed as long as the pointer to the map is trusted (when
using tracing programs) or is a const pointer to map, as in the following
example:
struct {
__uint(type, BPF_MAP_TYPE_HASH);
...
} hash SEC(".maps");
...
static inline int some_bpf_prog(void)
{
struct bpf_map *map = (struct bpf_map *)&hash;
__s64 count;
count = bpf_map_sum_elem_count(map);
...
}
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Link: https://lore.kernel.org/r/20230719092952.41202-5-aspsk@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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We use the map pointer only to read the counter values, no locking
involved, so mark the argument as const.
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Link: https://lore.kernel.org/r/20230719092952.41202-4-aspsk@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Add the BTF id of struct bpf_map to the reg2btf_ids array. This makes the
values of the CONST_PTR_TO_MAP type to be considered as trusted by kfuncs.
This, in turn, allows users to execute trusted kfuncs which accept `struct
bpf_map *` arguments from non-tracing programs.
While exporting the btf_bpf_map_id variable, save some bytes by defining
it as BTF_ID_LIST_GLOBAL_SINGLE (which is u32[1]) and not as BTF_ID_LIST
(which is u32[64]).
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Link: https://lore.kernel.org/r/20230719092952.41202-3-aspsk@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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A bpf_map_sum_elem_count kfunc was added to simplify getting the sum of the map
per-cpu element counters. If a map doesn't implement the counter, then the
function will always return 0.
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Link: https://lore.kernel.org/r/20230706133932.45883-3-aspsk@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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This patch introduce a flag MEM_RDONLY to tag a reg value
pointing to read-only memory. It makes the following changes:
1. PTR_TO_RDWR_BUF -> PTR_TO_BUF
2. PTR_TO_RDONLY_BUF -> PTR_TO_BUF | MEM_RDONLY
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-6-haoluo@google.com
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We have introduced a new type to make bpf_reg composable, by
allocating bits in the type to represent flags.
One of the flags is PTR_MAYBE_NULL which indicates a pointer
may be NULL. This patch switches the qualified reg_types to
use this flag. The reg_types changed in this patch include:
1. PTR_TO_MAP_VALUE_OR_NULL
2. PTR_TO_SOCKET_OR_NULL
3. PTR_TO_SOCK_COMMON_OR_NULL
4. PTR_TO_TCP_SOCK_OR_NULL
5. PTR_TO_BTF_ID_OR_NULL
6. PTR_TO_MEM_OR_NULL
7. PTR_TO_RDONLY_BUF_OR_NULL
8. PTR_TO_RDWR_BUF_OR_NULL
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211217003152.48334-5-haoluo@google.com
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For bpf_map_elem and bpf_sk_local_storage bpf iterators,
additional map_id should be shown for fdinfo and
userspace query. For example, the following is for
a bpf_map_elem iterator.
$ cat /proc/1753/fdinfo/9
pos: 0
flags: 02000000
mnt_id: 14
link_type: iter
link_id: 34
prog_tag: 104be6d3fe45e6aa
prog_id: 173
target_name: bpf_map_elem
map_id: 127
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200821184419.574240-1-yhs@fb.com
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Commit a5cbe05a6673 ("bpf: Implement bpf iterator for
map elements") added bpf iterator support for
map elements. The map element bpf iterator requires
info to identify a particular map. In the above
commit, the attr->link_create.target_fd is used
to carry map_fd and an enum bpf_iter_link_info
is added to uapi to specify the target_fd actually
representing a map_fd:
enum bpf_iter_link_info {
BPF_ITER_LINK_UNSPEC = 0,
BPF_ITER_LINK_MAP_FD = 1,
MAX_BPF_ITER_LINK_INFO,
};
This is an extensible approach as we can grow
enumerator for pid, cgroup_id, etc. and we can
unionize target_fd for pid, cgroup_id, etc.
But in the future, there are chances that
more complex customization may happen, e.g.,
for tasks, it could be filtered based on
both cgroup_id and user_id.
This patch changed the uapi to have fields
__aligned_u64 iter_info;
__u32 iter_info_len;
for additional iter_info for link_create.
The iter_info is defined as
union bpf_iter_link_info {
struct {
__u32 map_fd;
} map;
};
So future extension for additional customization
will be easier. The bpf_iter_link_info will be
passed to target callback to validate and generic
bpf_iter framework does not need to deal it any
more.
Note that map_fd = 0 will be considered invalid
and -EBADF will be returned to user space.
Fixes: a5cbe05a6673 ("bpf: Implement bpf iterator for map elements")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
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The bpf iterators for array and percpu array
are implemented. Similar to hash maps, for percpu
array map, bpf program will receive values
from all cpus.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184115.590532-1-yhs@fb.com
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The bpf iterators for hash, percpu hash, lru hash
and lru percpu hash are implemented. During link time,
bpf_iter_reg->check_target() will check map type
and ensure the program access key/value region is
within the map defined key/value size limit.
For percpu hash and lru hash maps, the bpf program
will receive values for all cpus. The map element
bpf iterator infrastructure will prepare value
properly before passing the value pointer to the
bpf program.
This patch set supports readonly map keys and
read/write map values. It does not support deleting
map elements, e.g., from hash tables. If there is
a user case for this, the following mechanism can
be used to support map deletion for hashtab, etc.
- permit a new bpf program return value, e.g., 2,
to let bpf iterator know the map element should
be removed.
- since bucket lock is taken, the map element will be
queued.
- once bucket lock is released after all elements under
this bucket are traversed, all to-be-deleted map
elements can be deleted.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184114.590470-1-yhs@fb.com
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The bpf iterator for map elements are implemented.
The bpf program will receive four parameters:
bpf_iter_meta *meta: the meta data
bpf_map *map: the bpf_map whose elements are traversed
void *key: the key of one element
void *value: the value of the same element
Here, meta and map pointers are always valid, and
key has register type PTR_TO_RDONLY_BUF_OR_NULL and
value has register type PTR_TO_RDWR_BUF_OR_NULL.
The kernel will track the access range of key and value
during verification time. Later, these values will be compared
against the values in the actual map to ensure all accesses
are within range.
A new field iter_seq_info is added to bpf_map_ops which
is used to add map type specific information, i.e., seq_ops,
init/fini seq_file func and seq_file private data size.
Subsequent patches will have actual implementation
for bpf_map_ops->iter_seq_info.
In user space, BPF_ITER_LINK_MAP_FD needs to be
specified in prog attr->link_create.flags, which indicates
that attr->link_create.target_fd is a map_fd.
The reason for such an explicit flag is for possible
future cases where one bpf iterator may allow more than
one possible customization, e.g., pid and cgroup id for
task_file.
Current kernel internal implementation only allows
the target to register at most one required bpf_iter_link_info.
To support the above case, optional bpf_iter_link_info's
are needed, the target can be extended to register such link
infos, and user provided link_info needs to match one of
target supported ones.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184112.590360-1-yhs@fb.com
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There is no functionality change for this patch.
Struct bpf_iter_reg is used to register a bpf_iter target,
which includes information for both prog_load, link_create
and seq_file creation.
This patch puts fields related seq_file creation into
a different structure. This will be useful for map
elements iterator where one iterator covers different
map types and different map types may have different
seq_ops, init/fini private_data function and
private_data size.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184109.590030-1-yhs@fb.com
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Currently, the pos pointer in bpf iterator map/task/task_file
seq_ops->start() is always incremented.
This is incorrect. It should be increased only if
*pos is 0 (for SEQ_START_TOKEN) since these start()
function actually returns the first real object.
If *pos is not 0, it merely found the object
based on the state in seq->private, and not really
advancing the *pos. This patch fixed this issue
by only incrementing *pos if it is 0.
Note that the old *pos calculation, although not
correct, does not affect correctness of bpf_iter
as bpf_iter seq_file->read() does not support llseek.
This patch also renamed "mid" in bpf_map iterator
seq_file private data to "map_id" for better clarity.
Fixes: 6086d29def80 ("bpf: Add bpf_map iterator")
Fixes: eaaacd23910f ("bpf: Add task and task/file iterator targets")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722195156.4029817-1-yhs@fb.com
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One additional field btf_id is added to struct
bpf_ctx_arg_aux to store the precomputed btf_ids.
The btf_id is computed at build time with
BTF_ID_LIST or BTF_ID_LIST_GLOBAL macro definitions.
All existing bpf iterators are changed to used
pre-compute btf_ids.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200720163403.1393551-1-yhs@fb.com
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Commit b121b341e598 ("bpf: Add PTR_TO_BTF_ID_OR_NULL
support") adds a field btf_id_or_null_non0_off to
bpf_prog->aux structure to indicate that the
first ctx argument is PTR_TO_BTF_ID reg_type and
all others are PTR_TO_BTF_ID_OR_NULL.
This approach does not really scale if we have
other different reg types in the future, e.g.,
a pointer to a buffer.
This patch enables bpf_iter targets registering ctx argument
reg types which may be different from the default one.
For example, for pointers to structures, the default reg_type
is PTR_TO_BTF_ID for tracing program. The target can register
a particular pointer type as PTR_TO_BTF_ID_OR_NULL which can
be used by the verifier to enforce accesses.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200513180221.2949882-1-yhs@fb.com
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Currently bpf_iter_reg_target takes parameters from target
and allocates memory to save them. This is really not
necessary, esp. in the future we may grow information
passed from targets to bpf_iter manager.
The patch refactors the code so target reg_info
becomes static and bpf_iter manager can just take
a reference to it.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200513180219.2949605-1-yhs@fb.com
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Implement seq_file operations to traverse all bpf_maps.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175909.2476096-1-yhs@fb.com
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