diff options
| author | Will Deacon <will.deacon@arm.com> | 2017-05-09 18:00:04 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-05-10 07:54:00 +0200 |
| commit | 88b0193d9418c00340e45e0a913a0813bc6c8c96 (patch) | |
| tree | 027a83b76832b465f3f120471ce58518e4fce2e0 /kernel | |
| parent | cefec668868be847ac3733c927ccd527c305b529 (diff) | |
perf/callchain: Force USER_DS when invoking perf_callchain_user()
Perf can generate and record a user callchain in response to a synchronous
request, such as a tracepoint firing. If this happens under set_fs(KERNEL_DS),
then we can end up walking the user stack (and dereferencing/saving whatever we
find there) without the protections usually afforded by checks such as
access_ok.
Rather than play whack-a-mole with each architecture's stack unwinding
implementation, fix the root of the problem by ensuring that we force USER_DS
when invoking perf_callchain_user from the perf core.
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/events/callchain.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index c04917cad1bf..1b2be63c8528 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -229,12 +229,18 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, } if (regs) { + mm_segment_t fs; + if (crosstask) goto exit_put; if (add_mark) perf_callchain_store_context(&ctx, PERF_CONTEXT_USER); + + fs = get_fs(); + set_fs(USER_DS); perf_callchain_user(&ctx, regs); + set_fs(fs); } } |