Messages in this thread Patch in this message | | | Date | Mon, 21 Mar 2016 02:51:03 -0700 | From | tip-bot for Peter Zijlstra <> | Subject | [tip:perf/urgent] perf/core: Fix Undefined behaviour in rb_alloc() |
| |
Commit-ID: 8184059e93c200757f5c0805dae0f14e880eab5d Gitweb: http://git.kernel.org/tip/8184059e93c200757f5c0805dae0f14e880eab5d Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Fri, 29 Jan 2016 15:17:51 +0100 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 21 Mar 2016 09:08:18 +0100
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> --- kernel/events/ring_buffer.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 1faad2c..c61f0cb 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);
| |