Commit 6e15eb3b authored May 03, 2013 by Peter Zijlstra Committed by Ingo Molnar May 04, 2013

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

parent 741a698f

arch/x86/kernel/cpu/perf_event_intel_lbr.c

+12 −2

Original line number	Diff line number	Diff line
		@@ -442,8 +442,18 @@ static int branch_type(unsigned long from, unsigned long to)
		return X86_BR_NONE;

		addr = buf;
		} else
		} 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