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authorPeter Zijlstra <peterz@infradead.org>2016-01-27 23:24:29 +0100
committerIngo Molnar <mingo@kernel.org>2016-01-29 08:35:23 +0100
commite01d8718de4170373cd7fbf5cf6f9cb61cebb1e9 (patch)
tree4ed51f0158d170fc54ca744aa6f24089d377266e /arch
parent6a3351b612b72c558910c88a43e2ef6d7d68bc97 (diff)
downloadlinux-e01d8718de4170373cd7fbf5cf6f9cb61cebb1e9.tar.bz2
perf/x86: Fix uninitialized value usage
When calling intel_alt_er() with .idx != EXTRA_REG_RSP_* we will not initialize alt_idx and then use this uninitialized value to index an array. When that is not fatal, it can result in an infinite loop in its caller __intel_shared_reg_get_constraints(), with IRQs disabled. Alternative error modes are random memory corruption due to the cpuc->shared_regs->regs[] array overrun, which manifest in either get_constraints or put_constraints doing weird stuff. Only took 6 hours of painful debugging to find this. Neither GCC nor Smatch warnings flagged this bug. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kan Liang <kan.liang@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Fixes: ae3f011fc251 ("perf/x86/intel: Fix SLM MSR_OFFCORE_RSP1 valid_mask") Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/perf_event_intel.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index a667078a5180..4264a084e59b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1960,7 +1960,8 @@ intel_bts_constraints(struct perf_event *event)
static int intel_alt_er(int idx, u64 config)
{
- int alt_idx;
+ int alt_idx = idx;
+
if (!(x86_pmu.flags & PMU_FL_HAS_RSP_1))
return idx;