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Date: Fri, 27 Apr 2018 15:58:09 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org,
syzbot+7c449856228b63ac951e@...kaller.appspotmail.com,
Jiri Olsa <jolsa@...nel.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Andi Kleen <andi@...stfloor.org>,
"H. Peter Anvin" <hpa@...or.com>,
Namhyung Kim <namhyung@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
syzkaller-bugs@...glegroups.com, x86@...nel.org,
Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 4.9 19/74] perf: Fix sample_max_stack maximum check
4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Olsa <jolsa@...nel.org>
commit 5af44ca53d019de47efe6dbc4003dd518e5197ed upstream.
The syzbot hit KASAN bug in perf_callchain_store having the entry stored
behind the allocated bounds [1].
We miss the sample_max_stack check for the initial event that allocates
callchain buffers. This missing check allows to create an event with
sample_max_stack value bigger than the global sysctl maximum:
# sysctl -a | grep perf_event_max_stack
kernel.perf_event_max_stack = 127
# perf record -vv -C 1 -e cycles/max-stack=256/ kill
...
perf_event_attr:
size 112
...
sample_max_stack 256
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 4
Note the '-C 1', which forces perf record to create just single event.
Otherwise it opens event for every cpu, then the sample_max_stack check
fails on the second event and all's fine.
The fix is to run the sample_max_stack check also for the first event
with callchains.
[1] https://marc.info/?l=linux-kernel&m=152352732920874&w=2
Reported-by: syzbot+7c449856228b63ac951e@...kaller.appspotmail.com
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: syzkaller-bugs@...glegroups.com
Cc: x86@...nel.org
Fixes: 97c79a38cd45 ("perf core: Per event callchain limit")
Link: http://lkml.kernel.org/r/20180415092352.12403-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
kernel/events/callchain.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -117,19 +117,22 @@ int get_callchain_buffers(int event_max_
goto exit;
}
+ /*
+ * If requesting per event more than the global cap,
+ * return a different error to help userspace figure
+ * this out.
+ *
+ * And also do it here so that we have &callchain_mutex held.
+ */
+ if (event_max_stack > sysctl_perf_event_max_stack) {
+ err = -EOVERFLOW;
+ goto exit;
+ }
+
if (count > 1) {
/* If the allocation failed, give up */
if (!callchain_cpus_entries)
err = -ENOMEM;
- /*
- * If requesting per event more than the global cap,
- * return a different error to help userspace figure
- * this out.
- *
- * And also do it here so that we have &callchain_mutex held.
- */
- if (event_max_stack > sysctl_perf_event_max_stack)
- err = -EOVERFLOW;
goto exit;
}
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