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This is long over-due: the __get_user() and __put_user() functions are
entirely historical, and are never the rigth thing to use any more. And
when mis-used (read: every case) they are not only slower than the right
thing, but also insecure because they don't check the user address
range.
Most of the usage sites have been converted long ago, but various
left-overs remained. So this started out as a single patch that I wrote
as a "show people how to convert __{get,put}_user() to modern code".
In particular, Thomas last year implemented the very nice new scoped
user access region helpers (see commit e497310b4ffb: "uaccess: Provide
scoped user access regions") that makes the modern interfaces
particularly easy to use and really removes any excuse for the old
horrors.
That small example patch then grew to this, partly using Claude as a
glorified coccinelle script to apply the pattern to other places.
There were a few different reasons for using __put_user() and
__get_user() rather than the alternatives, but the original historical
one was performance: when doing multiple accesses off the same base
pointer, doing a single range check followed by multiple non-checked
accesses used to create smaller and faster code.
The keyword here is "used to". It hasn't been true for years, because
the range check isn't actually the real cost these days. The real cost
of user accesses on modern hardware is turning the user accesses on and
off in the first place (on x86, using the STAC/CLAC instructions).
Those sequences get turned into 'scoped_user_read_access() { }' blocks,
see for example that first patch in the series: "signal: use scoped user
access for old-style sigaction".
Another, historical reason for using __get_user() and friends is that
you actually want to do a kernel pointer access, but the pointer might
not be entirely reliable (typically during fault handling), so you want
to have exception handling for the kernel access.
The modern way to do that kind of non-faulting kernel access is using
"get_kernel_nofault()", but some code predates that helper existing at
all, and used __get_user() as a way to just get a memory access with
exception handling. For that pattern, see for example "alpha: use
get_kernel_nofault() in dik_show_code()"
A third bad reason for using __get_user() and friends was that the
proper get_user() had a "might_fault()" in it, and code that ran in
atomic regions but hadn't disabled page faults would result in a
warning. That kind of code needs to explicitly disable page faults,
because "atomic region" is not well defined at run-time and can be
invisible (eg a preempt-off region in a non-preemptible kernel).
See "vdpa_sim: disable page faults around vringh_need_notify_iotlb()"
for an example of that pattern, where the local_bh_disable() now also
grows a pagefault_disable(), which makes the normal get_user() no longer
warn about the user access in non-process context, because it can see
that the potential page fault will not cause problems.
And finally, the really nasty reason to use __get_user() and friends:
pointers that can be either kernel pointers or user pointers. We've
gotten rid of almost all such cases, but a couple remained. See for
example "x86/sev: Use explicit user-or-kernel accessors for #VC memory
operands".
NOTE! This series removes all __get/put_user() calls from generic code
but only does the final removal of the whole interface on x86. Other
architectures have not been entirely converted, for a variety of reasons:
- arm64 makes __{get,put}_user() be exactly the same as
{get,put}_user() so it's harmless and didn't have the dangers of the
legacy use cases.
- any architecture that uses <asm-generic/uaccess.h> will still use
__{get,put}_user as the underlying helper function name
- several architectures had some legacy uses that weren't entirely
trivial and I didn't want to extend this patch series to things that
I don't know and that don't really matter.
but I did do a couple of the obvious "follows the exact same pattern"
just because it could be done mindlessly and automatically.
Let's see if I broke anything, but we should have done this years ago.
* uaccess-cleanups: (48 commits)
drm/i915/gem: ignore errors on presumed_offset write-back
powerpc/align: use get_user_instr() for a user-mode instruction
powerpc/signal64: use scoped user access in setup_trampoline()
powerpc/signal64: use get_user() for the single context reads
powerpc/signal32: use get_user() for the single context reads
KVM: PPC: Book3S HV: use get_user()/put_user() for the HPT fd
powerpc/powernv: use get_user()/put_user() in the LPC debugfs files
s390: use get_user()/put_user() instead of the unchecked variants
ARM: OABI: use scoped user access in epoll_put_uevent()
ARM: signal: stop using __put_user() for the signal frame
ARM: signal: check the FDPIC function descriptor address
alpha: split the prefetch check in do_page_fault() by mode
openrisc: use get_kernel_nofault() in show_registers()
alpha: use get_kernel_nofault() in dik_show_code()
nios2: use scoped user access for the signal frame
nios2: check the signal frame address before writing to it
hexagon: use scoped user access for the signal frame
alpha: use scoped user access when setting up signal frames
alpha: use scoped user access in the sigreturn path
alpha: use scoped user access in osf_sigaction()
...
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setup_sigcontext() writes the whole register set with __put_user() and
__copy_to_user(), OR-ing the errors together, relying on its callers'
access_ok() on the frame. setup_frame() and setup_rt_frame() write the
sigreturn trampoline, and setup_rt_frame() the ucontext header, the
same way.
Do those writes inside scoped_user_write_access() with
unsafe_put_user() and unsafe_copy_to_user(). on_sig_stack() is
evaluated before the scope, and the instruction cache flush stays
outside it. The up-front access_ok()
calls stay: setup_rt_frame() still needs its own for the
__copy_to_user() of the signal mask.
A fault part way through now stops at the first failing write instead of
carrying on. Either way the frame setup fails and the task gets
SIGSEGV. alpha has no user_access_begin(), so the accesses themselves
are the same as before.
This is part of getting rid of __get_user() and __put_user() entirely.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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restore_sigcontext() reads the whole saved register set with
__get_user() and __copy_from_user(), OR-ing the errors together. It
relies on its callers having done access_ok(): do_sigreturn() on the
sigcontext, do_rt_sigreturn() on the enclosing ucontext.
Make it do its own check, with a scoped_user_read_access() around
unsafe_get_user() and unsafe_copy_from_user(). do_sigreturn() then only
needs the same for the signal mask. do_rt_sigreturn() keeps its
access_ok(), which its own __copy_from_user() of the mask still needs.
A fault part way through the frame now stops the restore there, instead
of carrying on with zeroes and still writing the user stack pointer.
Either way the sigreturn fails and the task gets SIGSEGV. alpha has no
user_access_begin(), so the accesses themselves are the same as before.
This is part of getting rid of __get_user() and __put_user() entirely.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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osf_sigaction() does one access_ok() on each user structure and then
reads or writes its fields with __get_user() or __put_user(), the same
pattern as the generic old-style sigaction().
Convert it the same way, to scoped_user_{read,write}_access() with
unsafe_{get,put}_user(). alpha has no user_access_begin(), so the
scope is the same access_ok() followed by the same plain accesses, and
the generated code does not change.
This is part of getting rid of __get_user() and __put_user() entirely.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Wire Alpha into the generic entry code for syscall entry/exit and
return-to-user handling, while keeping the low-level PALcode return paths
Alpha-specific.
Move most of the syscall entry/exit logic out of entSys and into C helpers
built around the generic entry API. Syscall entry now uses
syscall_enter_from_user_mode(), records Alpha-local syscall metadata in
thread_info, handles the ptrace/seccomp skip decision, and selects the
syscall table target in C. The final target call remains in entry.S so
Alpha can preserve its existing syscall ABI and assembly syscall-table
wrappers.
On return from syscalls, finish Alpha's r0/r19 result encoding and
skipped-syscall restart handling in C before calling
syscall_exit_to_user_mode(). Non-syscall returns to user mode use a
separate alpha_exit_to_user_mode() helper, which disables interrupts,
runs irqentry_exit_to_user_mode_prepare(), and then enters the common
exit_to_user_mode() path.
Keep the remaining PALcode restore handling in assembly. In particular,
kernel-mode returns still need Alpha-specific lockdep IRQ-state annotation
based on the saved processor status, while user-mode returns are handed to
the generic exit-to-user code.
Add the generic-entry support bits needed by common code, including
thread_info.syscall_work, syscall trace support, ptrace sysemu request
numbers, and arch_syscall_is_vdso_sigreturn().
This has been tested by booting Alpha with GENERIC_ENTRY enabled, checking
lockdep IRQ-state accounting, running fork/clone-heavy package builds, and
running the seccomp as well as strace test suites.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
Link: https://lore.kernel.org/r/20260902184058.198679-2-linmag7@gmail.com
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
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Alpha masks interrupts through the PAL IPL state, so lockdep cannot infer
hardirq state transitions from generic code alone. Add explicit
hardirq on/off annotations to the low-level entry and return paths so
lockdep's IRQ state follows the hardware IPL state.
Annotate the PAL IPL transitions and the shared return-to-user/kernel
paths where interrupts become enabled or disabled. With the preceding
irqflags, raw-lock, sysfs, and ftrace return-address preparations in
place, select LOCKDEP_SUPPORT and TRACE_IRQFLAGS_SUPPORT for Alpha.
This keeps CONFIG_PROVE_LOCKING usable on Alpha instead of disabling
debug_locks due to IRQ-state mismatches.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Tested-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
Link: https://lore.kernel.org/r/20260706170019.2941459-7-linmag7@gmail.com
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
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On each context switch we save the FPU registers on stack
of old process and restore FPU registers from the stack of new one.
That allows us to avoid doing that each time we enter/leave the
kernel mode; however, that can get suboptimal in some cases.
For one thing, we don't need to bother saving anything
for kernel threads. For another, if between entering and leaving
the kernel a thread gives CPU up more than once, it will do
useless work, saving the same values every time, only to discard
the saved copy as soon as it returns from switch_to().
Alternative solution:
* move the array we save into from switch_stack to thread_info
* have a (thread-synchronous) flag set when we save them
* have another flag set when they should be restored on return to userland.
* do *NOT* save/restore them in do_switch_stack()/undo_switch_stack().
* restore on the exit to user mode if the restore flag had
been set. Clear both flags.
* on context switch, entry to fork/clone/vfork, before entry into do_signal()
and on entry into straced syscall save the registers and set the 'saved' flag
unless it had been already set.
* on context switch set the 'restore' flag as well.
* have copy_thread() set both flags for child, so the registers would be
restored once the child returns to userland.
* use the saved data in setup_sigcontext(); have restore_sigcontext() set both flags
and copy from sigframe to save area.
* teach ptrace to look for FPU registers in thread_info instead of
switch_stack.
* teach isolated accesses to FPU registers (rdfpcr, wrfpcr, etc.)
to check the 'saved' flag (under preempt_disable()) and work with the save area
if it's been set; if 'saved' flag is found upon write access, set 'restore' flag
as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Matt Turner <mattst88@gmail.com>
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Move set_notify_resume and tracehook_notify_resume into resume_user_mode.h.
While doing that rename tracehook_notify_resume to resume_user_mode_work.
Update all of the places that included tracehook.h for these functions to
include resume_user_mode.h instead.
Update all of the callers of tracehook_notify_resume to call
resume_user_mode_work.
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-12-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.
To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.
Convert them all to the new flag accessor helpers.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Link: https://lore.kernel.org/r/20211129130653.2037928-5-mark.rutland@arm.com
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While reviewing the signal handlers on alpha it became clear that
si_trapno is only set to a non-zero value when sending SIGFPE and when
sending SITGRAP with si_code TRAP_UNK.
Add send_sig_fault_trapno and send SIGTRAP TRAP_UNK, and SIGFPE with it.
Remove the define of __ARCH_SI_TRAPNO and remove the always zero
si_trapno parameter from send_sig_fault and force_sig_fault.
v1: https://lkml.kernel.org/r/m1eeers7q7.fsf_-_@fess.ebiederm.org
v2: https://lkml.kernel.org/r/20210505141101.11519-7-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/87h7gvxx7l.fsf_-_@disp2133
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Wire up TIF_NOTIFY_SIGNAL handling for alpha.
Cc: linux-alpha@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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All the callers currently do this, clean it up and move the clearing
into tracehook_notify_resume() instead.
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.
[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
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All of the remaining callers pass current into force_sig so
remove the task parameter to make this obvious and to make
misuse more difficult in the future.
This also makes it clear force_sig passes current into force_sig_info.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.
It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access. But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.
A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model. And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.
This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.
There were a couple of notable cases:
- csky still had the old "verify_area()" name as an alias.
- the iter_iov code had magical hardcoded knowledge of the actual
values of VERIFY_{READ,WRITE} (not that they mattered, since nothing
really used it)
- microblaze used the type argument for a debug printout
but other than those oddities this should be a total no-op patch.
I tried to fix up all architectures, did fairly extensive grepping for
access_ok() uses, and the changes are trivial, but I may have missed
something. Any missed conversion should be trivially fixable, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Filling in struct siginfo before calling send_sig_info a tedious and
error prone process, where once in a great while the wrong fields
are filled out, and siginfo has been inconsistently cleared.
Simplify this process by using the helper send_sig_fault. Which
takes as a parameters all of the information it needs, ensures
all of the fiddly bits of filling in struct siginfo are done properly
and then calls send_sig_info.
In short about a 5 line reduction in code for every time send_sig_info
is called, which makes the calling function clearer.
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: linux-alpha@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Call clear_siginfo to ensure every stack allocated siginfo is properly
initialized before being passed to the signal sending functions.
Note: It is not safe to depend on C initializers to initialize struct
siginfo on the stack because C is allowed to skip holes when
initializing a structure.
The initialization of struct siginfo in tracehook_report_syscall_exit
was moved from the helper user_single_step_siginfo into
tracehook_report_syscall_exit itself, to make it clear that the local
variable siginfo gets fully initialized.
In a few cases the scope of struct siginfo has been reduced to make it
clear that siginfo siginfo is not used on other paths in the function
in which it is declared.
Instances of using memset to initialize siginfo have been replaced
with calls clear_siginfo for clarity.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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<linux/sched/task_stack.h>
We are going to split <linux/sched/task_stack.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task_stack.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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<linux/sched/signal.h>
We are going to split <linux/sched/signal.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/signal.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This was entirely automated, using the script by Al:
PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>'
sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \
$(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)
to do the replacement at the end of the merge window.
Requested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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If an attacker can cause a controlled kernel stack overflow, overwriting
the restart block is a very juicy exploit target. This is because the
restart_block is held in the same memory allocation as the kernel stack.
Moving the restart block to struct task_struct prevents this exploit by
making the restart_block harder to locate.
Note that there are other fields in thread_info that are also easy
targets, at least on some architectures.
It's also a decent simplification, since the restart code is more or less
identical on all architectures.
[james.hogan@imgtec.com: metag: align thread_info::supervisor_stack]
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: David Miller <davem@davemloft.net>
Acked-by: Richard Weinberger <richard@nod.at>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Steven Miao <realmz6@gmail.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Aurelien Jacquiot <a-jacquiot@ti.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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... and use the new helpers
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and now the asm glue side of that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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It's needed only in setup_sigcontext() and it's always reg - <constant>;
no point passing it all way down through the call chain. This is just
the signal.c side of that stuff; next will come the asm glue one...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Turn the slow side of work_pending into C function, including all
the looping. What we get out of that:
* we do _not_ call get_signal_to_deliver() with IRQs disabled
anymore
* no need to save/restore volatiles on each pass if there
turns to be more than one (unlikely, but still)
* all double-restart prevention is in C now.
* glue gets simpler.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Does block_sigmask() + tracehook_signal_handler(); called when
sigframe has been successfully built. All architectures converted
to it; block_sigmask() itself is gone now (merged into this one).
I'm still not too happy with the signature, but that's a separate
story (IMO we need a structure that would contain signal number +
siginfo + k_sigaction, so that get_signal_to_deliver() would fill one,
signal_delivered(), handle_signal() and probably setup...frame() -
take one).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Only 3 out of 63 do not. Renamed the current variant to __set_current_blocked(),
added set_current_blocked() that will exclude unblockable signals, switched
open-coded instances to it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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replace boilerplate "should we use ->saved_sigmask or ->blocked?"
with calls of obvious inlined helper...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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first fruits of ..._restore_sigmask() helpers: now we can take
boilerplate "signal didn't have a handler, clear RESTORE_SIGMASK
and restore the blocked mask from ->saved_mask" into a common
helper. Open-coded instances switched...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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* move force_sigsegv() (from setup...frame()) and clearing RESTART_SIGMASK
(from do_signal()) into hanlde_signal()
* get rid of handle_signal() return value and oldset argument
* checking for TIF_SIGPENDING is enough; set_restart_sigmask() sets this
one as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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guts of saved_sigmask-based sigsuspend/rt_sigsuspend. Takes
kernel sigset_t *.
Open-coded instances replaced with calling it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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As described in e6fa16ab9c1e ("signal: sigprocmask() should do
retarget_shared_pending()") the modification of current->blocked is
incorrect as we need to check for shared signals we're about to block.
Also, use the new helper function introduced in commit 5e6292c0f28f
("signal: add block_sigmask() for adding sigmask to current->blocked")
which centralises the code for updating current->blocked after
successfully delivering a signal and reduces the amount of duplicate
code across architectures. In the past some architectures got this code
wrong, so using this helper function should stop that from happening
again.
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit c52c2ddc1dfa ("alpha: switch osf_sigprocmask() to use of
sigprocmask()") had several problems. The more obvious compile issues
got fixed in commit 0f44fbd297e1 ("alpha: fix compile problem in
arch/alpha/kernel/signal.c"), but it also caused a regression.
Since _BLOCKABLE is already the set of signals that can be blocked, the
code should do "newmask & _BLOCKABLE" rather than inverting _BLOCKABLE
before masking.
Reported-by: Michael Cree <mcree@orcon.net.nz>
Patch-by: Al Viro <viro@zeniv.linux.org.uk>
Patch-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tssk. Apparently Al hadn't checked commit c52c2ddc1dfa ("alpha: switch
osf_sigprocmask() to use of sigprocmask()") at all. It doesn't compile.
Fixed as per suggestions from Michael Cree.
Reported-by: Michael Cree <mcree@orcon.net.nz>
Cc: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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get rid of a useless wrapper, while we are at it
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Old code used to set regs->r0 and regs->r19 to force the right
return value. Leaving that after switch to ERESTARTNOHAND
was a Bad Idea(tm), since now that screws the restart - if we
hit the case when get_signal_to_deliver() returns 0, we will
step back to syscall insn, with v0 set to EINTR and a3 to 1.
The latter won't matter, since EINTR is 4, aka __NR_write.
Testcase:
#include <signal.h>
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
main()
{
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, SIGCONT);
sigprocmask(SIG_SETMASK, &mask, NULL);
kill(0, SIGCONT);
syscall(__NR_sigsuspend, 1, "b0rken\n", 7);
}
results on alpha in immediate message to stdout...
Fix is obvious; moreover, since we don't need regs anymore, we can
switch to normal prototypes for these guys and lose the wrappers.
Even better, rt_sigsuspend() is identical to generic version in
kernel/signal.c now.
Tested-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Matt Turner <mattst88@gmail.com>
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same thing as had been done on other targets back in 2003 -
move setting ->restart_block.fn into {rt_,}sigreturn().
Tested-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Matt Turner <mattst88@gmail.com>
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Add #inclusions of linux/tracehook.h to those arch files that had the tracehook
call for TIF_NOTIFY_RESUME added when support for that flag was added to that
arch.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Add a keyctl to install a process's session keyring onto its parent. This
replaces the parent's session keyring. Because the COW credential code does
not permit one process to change another process's credentials directly, the
change is deferred until userspace next starts executing again. Normally this
will be after a wait*() syscall.
To support this, three new security hooks have been provided:
cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
the blank security creds and key_session_to_parent() - which asks the LSM if
the process may replace its parent's session keyring.
The replacement may only happen if the process has the same ownership details
as its parent, and the process has LINK permission on the session keyring, and
the session keyring is owned by the process, and the LSM permits it.
Note that this requires alteration to each architecture's notify_resume path.
This has been done for all arches barring blackfin, m68k* and xtensa, all of
which need assembly alteration to support TIF_NOTIFY_RESUME. This allows the
replacement to be performed at the point the parent process resumes userspace
execution.
This allows the userspace AFS pioctl emulation to fully emulate newpag() and
the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
alter the parent process's PAG membership. However, since kAFS doesn't use
PAGs per se, but rather dumps the keys into the session keyring, the session
keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
the newpag flag.
This can be tested with the following program:
#include <stdio.h>
#include <stdlib.h>
#include <keyutils.h>
#define KEYCTL_SESSION_TO_PARENT 18
#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)
int main(int argc, char **argv)
{
key_serial_t keyring, key;
long ret;
keyring = keyctl_join_session_keyring(argv[1]);
OSERROR(keyring, "keyctl_join_session_keyring");
key = add_key("user", "a", "b", 1, keyring);
OSERROR(key, "add_key");
ret = keyctl(KEYCTL_SESSION_TO_PARENT);
OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");
return 0;
}
Compiled and linked with -lkeyutils, you should see something like:
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: _ses
355907932 --alswrv 4043 -1 \_ keyring: _uid.4043
[dhowells@andromeda ~]$ /tmp/newpag
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: _ses
1055658746 --alswrv 4043 4043 \_ user: a
[dhowells@andromeda ~]$ /tmp/newpag hello
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: hello
340417692 --alswrv 4043 4043 \_ user: a
Where the test program creates a new session keyring, sticks a user key named
'a' into it and then installs it on its parent.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Implement TIF_NOTIFY_RESUME for most of those architectures in which isn't yet
available, and, whilst we're at it, have it call the appropriate tracehook.
After this patch, blackfin, m68k* and xtensa still lack support and need
alteration of assembly code to make it work.
Resume notification can then be used (by a later patch) to install a new
session keyring on the parent of a process.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
cc: linux-arch@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
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Convert OSF syscalls and add alpha specific SYSCALL_ALIAS() macro.
Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Some of the new syscalls require supporting TIF_RESTORE_SIGMASK.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove includes of <linux/smp_lock.h> where it is not used/needed.
Suggested by Al Viro.
Builds cleanly on x86_64, i386, alpha, ia64, powerpc, sparc,
sparc64, and arm (all 59 defconfigs).
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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