| From | Luis Henriques <> | Subject | [PATCH 039/115] perf/x86/intel/lbr: Fix LBR filter | Date | Mon, 20 May 2013 11:50:39 +0100 |
| |
3.5.7.13 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
commit 6e15eb3ba6c0249c9e8c783517d131b47db995ca upstream.
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: 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 Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- 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 520b426..62a93a4 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 -- 1.8.1.2
|