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| author | Peter Zijlstra <peterz@infradead.org> | 2016-01-27 23:24:29 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-01-29 08:35:23 +0100 |
| commit | e01d8718de4170373cd7fbf5cf6f9cb61cebb1e9 (patch) | |
| tree | 4ed51f0158d170fc54ca744aa6f24089d377266e /arch | |
| parent | perf: Fix race in perf_event_exit_task_context() (diff) | |
| download | linux-e01d8718de4170373cd7fbf5cf6f9cb61cebb1e9.tar.xz linux-e01d8718de4170373cd7fbf5cf6f9cb61cebb1e9.zip | |
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.c | 3 |
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; |