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Revert "net: ptr_ring: otherwise safe empty checks can overrun array bounds"

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This reverts commit bcecb4bbf8.

If we try to allocate an extra entry as the above commit did, and when
the requested size is UINT_MAX, addition overflows causing zero size to
be passed to kmalloc().

kmalloc then returns ZERO_SIZE_PTR with a subsequent crash.

Reported-by: syzbot+87678bcf753b44c39b67@syzkaller.appspotmail.com
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin 2018-01-26 01:36:35 +02:00 • committed by David S. Miller
parent 84328342a7
commit 9fb582b670
1 changed files with 1 additions and 6 deletions
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7
include/linux/ptr_ring.h
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@ -466,12 +466,7 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp) static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
{ {
/* Allocate an extra dummy element at end of ring to avoid consumer head return kcalloc(size, sizeof(void *), gfp);
* or produce head access past the end of the array. Possible when
* producer/consumer operations and __ptr_ring_peek operations run in
* parallel.
*/
return kcalloc(size + 1, sizeof(void *), gfp);
} }
static inline void __ptr_ring_set_size(struct ptr_ring *r, int size) static inline void __ptr_ring_set_size(struct ptr_ring *r, int size)