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 either stop using modules as
all sane people do or optimize it using an RCU backed rb-tree.
Reported-by: Andi Kleen <[email protected]>
Cc: [email protected]
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
---
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- 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 fro
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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