lkml.org 
[lkml]   [2016]   [Sep]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:perf/urgent] perf/x86/intel/bts: Make sure debug store is valid
Commit-ID:  f1e1c9e5e357c05253affb13be29285c5cb56bf0
Gitweb: http://git.kernel.org/tip/f1e1c9e5e357c05253affb13be29285c5cb56bf0
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Tue, 20 Sep 2016 15:12:21 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 20 Sep 2016 16:06:09 +0200

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: [<ffffffff8100c463>] intel_bts_interrupt+0x43/0x130
| Call Trace:
| <NMI> d [<ffffffff8100b341>] intel_pmu_handle_irq+0x51/0x4b0
| [<ffffffff81004d47>] 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 <bigeasy@linutronix.de>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: vince@deater.net
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/20160920131220.xg5pbdjtznszuyzb@breakpoint.cc
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
arch/x86/events/intel/bts.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index bdcd651..6ff66ef 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;

/*
\
 
 \ /
  Last update: 2016-09-20 16:16    [W:0.837 / U:0.000 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site