diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2016-01-29 15:17:51 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-03-21 09:08:18 +0100 |
| commit | 8184059e93c200757f5c0805dae0f14e880eab5d (patch) | |
| tree | 3dda3b01c57dd182c663b2700819deeb60cbe390 /kernel/events/ring_buffer.c | |
| parent | perf/x86/BTS: Fix RCU usage (diff) | |
| download | linux-8184059e93c200757f5c0805dae0f14e880eab5d.tar.xz linux-8184059e93c200757f5c0805dae0f14e880eab5d.zip | |
perf/core: Fix Undefined behaviour in rb_alloc()
Sasha reported:
[ 3494.030114] UBSAN: Undefined behaviour in kernel/events/ring_buffer.c:685:22
[ 3494.030647] shift exponent -1 is negative
Andrey spotted that this is because:
It happens if nr_pages = 0:
rb->page_order = ilog2(nr_pages);
Fix it by making both assignments conditional on nr_pages; since
otherwise they should both be 0 anyway, and will be because of the
kzalloc() used to allocate the structure.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Reported-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.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>
Link: http://lkml.kernel.org/r/20160129141751.GA407@worktop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/ring_buffer.c')
| -rw-r--r-- | kernel/events/ring_buffer.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 1faad2cfdb9e..c61f0cbd308b 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -746,8 +746,10 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) rb->user_page = all_buf; rb->data_pages[0] = all_buf + PAGE_SIZE; - rb->page_order = ilog2(nr_pages); - rb->nr_pages = !!nr_pages; + if (nr_pages) { + rb->nr_pages = 1; + rb->page_order = ilog2(nr_pages); + } ring_buffer_init(rb, watermark, flags); |