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| author | Alexander Shishkin <alexander.shishkin@linux.intel.com> | 2015-08-31 17:09:28 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-09-13 11:27:22 +0200 |
| commit | d2878d642a4edd1d57c691dc3e4d7847cbf9d442 (patch) | |
| tree | 7eb6b29412ee022b6e64dec4cb81080513bfa713 /arch | |
| parent | a09d31f45224c219a4d5c728fa40150dc9d3e3e5 (diff) | |
| download | linux-d2878d642a4edd1d57c691dc3e4d7847cbf9d442.tar.bz2 | |
perf/x86/intel/bts: Disallow use by unprivileged users on paranoid systems
BTS leaks kernel addresses even in userspace-only mode due to imprecise IP
sampling, so sometimes syscall entry points or page fault handler addresses
end up in a userspace trace.
Now, intel_bts driver exports trace data zero-copy, it does not scan through
it to filter out the kernel addresses and it's would be a O(n) job.
To work around this situation, this patch forbids the use of intel_bts
driver by unprivileged users on systems with the paranoid setting above the
(kernel's) default "1", which still allows kernel profiling. In other words,
using intel_bts driver implies kernel tracing, regardless of the
"exclude_kernel" attribute setting.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/1441030168-6853-3-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event_intel_bts.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_intel_bts.c b/arch/x86/kernel/cpu/perf_event_intel_bts.c index d1c0f254afbe..2cad71d1b14c 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_bts.c +++ b/arch/x86/kernel/cpu/perf_event_intel_bts.c @@ -495,6 +495,19 @@ static int bts_event_init(struct perf_event *event) if (x86_add_exclusive(x86_lbr_exclusive_bts)) return -EBUSY; + /* + * BTS leaks kernel addresses even when CPL0 tracing is + * disabled, so disallow intel_bts driver for unprivileged + * users on paranoid systems since it provides trace data + * to the user in a zero-copy fashion. + * + * Note that the default paranoia setting permits unprivileged + * users to profile the kernel. + */ + if (event->attr.exclude_kernel && perf_paranoid_kernel() && + !capable(CAP_SYS_ADMIN)) + return -EACCES; + ret = x86_reserve_hardware(); if (ret) { x86_del_exclusive(x86_lbr_exclusive_bts); |