diff options
| author | Jiri Olsa <jolsa@kernel.org> | 2018-04-15 11:23:51 +0200 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2018-04-17 09:47:40 -0300 |
| commit | 5af44ca53d019de47efe6dbc4003dd518e5197ed (patch) | |
| tree | 4cbc50c2ff819adbbb4cd27648576ae9709b6e32 /kernel/events | |
| parent | 78b562fbfa2cf0a9fcb23c3154756b690f4905c1 (diff) | |
perf: Fix sample_max_stack maximum check
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@syzkaller.appspotmail.com
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: syzkaller-bugs@googlegroups.com
Cc: x86@kernel.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@redhat.com>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/callchain.c | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 772a43fea825..73cc26e321de 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -119,19 +119,22 @@ int get_callchain_buffers(int event_max_stack) 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; } |