path: root/arch
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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2013-05-03 14:11:24 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-05-11 07:18:21 -0700
commitd851a41c72181e5170a3a81fa124c678bd449a1c (patch)
treee4bd48ff5564e296ba27d5a9a33db0fc730804b5 /arch
parent1a2d6c494667deb43c5dfca27b719a1446a1d641 (diff)
perf/x86/intel/lbr: Fix LBR filter
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
1 files 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 da02e9cc375..de341d4ec92 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