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perf/core: Fix possible Spectre-v1 indexing for ->aux_pages[]

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> kernel/events/ring_buffer.c:871 perf_mmap_to_page() warn: potential spectre issue 'rb->aux_pages'

Userspace controls @pgoff through the fault address. Sanitize the
array index before doing the array dereference.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2018-04-20 14:03:18 +02:00 committed by Ingo Molnar
parent 354d779307
commit 4411ec1d19
1 changed files with 5 additions and 2 deletions
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7
kernel/events/ring_buffer.c
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@ -14,6 +14,7 @@
#include <linux/slab.h>
#include <linux/circ_buf.h>
#include <linux/poll.h>
#include <linux/nospec.h>
#include "internal.h"
@ -867,8 +868,10 @@ perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
return NULL;
/* AUX space */
if (pgoff >= rb->aux_pgoff)
return virt_to_page(rb->aux_pages[pgoff - rb->aux_pgoff]);
if (pgoff >= rb->aux_pgoff) {
int aux_pgoff = array_index_nospec(pgoff - rb->aux_pgoff, rb->aux_nr_pages);
return virt_to_page(rb->aux_pages[aux_pgoff]);
}
}
return __perf_mmap_to_page(rb, pgoff);