From: Sebastian Andrzej Siewior Date: Tue, 20 Sep 2016 13:12:21 +0000 (+0200) Subject: perf/x86/intel/bts: Make sure debug store is valid X-Git-Tag: v4.8-rc8~8^2~2 X-Git-Url: http://git.cascardo.info/?p=cascardo%2Flinux.git;a=commitdiff_plain;h=f1e1c9e5e357c05253affb13be29285c5cb56bf0 perf/x86/intel/bts: Make sure debug store is valid Since commit 4d4c47412464 ("perf/x86/intel/bts: Fix BTS PMI detection") my box goes boom on boot: | .... node #0, CPUs: #1 #2 #3 #4 #5 #6 #7 | BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 | IP: [] intel_bts_interrupt+0x43/0x130 | Call Trace: | d [] intel_pmu_handle_irq+0x51/0x4b0 | [] perf_event_nmi_handler+0x27/0x40 This happens because the code introduced in this commit dereferences the debug store pointer unconditionally. The debug store is not guaranteed to be available, so a NULL pointer check as on other places is required. Fixes: 4d4c47412464 ("perf/x86/intel/bts: Fix BTS PMI detection") Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: vince@deater.net Cc: eranian@google.com Link: http://lkml.kernel.org/r/20160920131220.xg5pbdjtznszuyzb@breakpoint.cc Signed-off-by: Thomas Gleixner --- diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c index bdcd6510992c..6ff66efa0feb 100644 --- a/arch/x86/events/intel/bts.c +++ b/arch/x86/events/intel/bts.c @@ -455,7 +455,7 @@ int intel_bts_interrupt(void) * The only surefire way of knowing if this NMI is ours is by checking * the write ptr against the PMI threshold. */ - if (ds->bts_index >= ds->bts_interrupt_threshold) + if (ds && (ds->bts_index >= ds->bts_interrupt_threshold)) handled = 1; /*