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authorWill Deacon <will.deacon@arm.com>2017-05-09 18:00:04 +0100
committerIngo Molnar <mingo@kernel.org>2017-05-10 07:54:00 +0200
commit88b0193d9418c00340e45e0a913a0813bc6c8c96 (patch)
tree027a83b76832b465f3f120471ce58518e4fce2e0 /kernel/events
parentcefec668868be847ac3733c927ccd527c305b529 (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/events')
-rw-r--r--kernel/events/callchain.c6
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);
}
}