Messages in this thread Patch in this message | | | Date | Sat, 4 May 2013 01:21:45 -0700 | From | tip-bot for Peter Zijlstra <> | Subject | [tip:perf/urgent] perf/x86/intel/lbr: Fix LBR filter |
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Commit-ID: 6e15eb3ba6c0249c9e8c783517d131b47db995ca Gitweb: http://git.kernel.org/tip/6e15eb3ba6c0249c9e8c783517d131b47db995ca Author: Peter Zijlstra <a.p.zijlstra@chello.nl> AuthorDate: Fri, 3 May 2013 14:11:24 +0200 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Sat, 4 May 2013 08:37:47 +0200
perf/x86/intel/lbr: Fix LBR filter
The LBR 'from' adddress is under full userspace control; ensure we validate it before reading from it.
Note: is_module_text_address() can potentially be quite expensive; for those running into that with high overhead in modules optimize it using an RCU backed rb-tree.
Reported-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: <stable@kernel.org> Cc: eranian@google.com Link: http://lkml.kernel.org/r/20130503121256.158211806@chello.nl Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: http://lkml.kernel.org/n/tip-mk8i82ffzax01cnqo829iy1q@git.kernel.org --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index da02e9c..de341d4 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -442,8 +442,18 @@ static int branch_type(unsigned long from, unsigned long to) return X86_BR_NONE; addr = buf; - } else - addr = (void *)from; + } else { + /* + * The LBR logs any address in the IP, even if the IP just + * faulted. This means userspace can control the from address. + * Ensure we don't blindy read any address by validating it is + * a known text address. + */ + if (kernel_text_address(from)) + addr = (void *)from; + else + return X86_BR_NONE; + } /* * decoder needs to know the ABI especially
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