Re: [PATCH net-next 06/12] Revert "net: ptr_ring: otherwise safe empty checks can overrun array bounds"
From: John Fastabend <john.fastabend@gmail.com>
Date: 2018-01-26 00:13:07
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On 01/25/2018 03:36 PM, Michael S. Tsirkin wrote:
This reverts commit bcecb4bbf88aa03171c30652bca761cf27755a6b. 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> ---
Dang, I missed this case. Thanks. Acked-by: John Fastabend <john.fastabend@gmail.com>
quoted hunk ↗ jump to hunk
include/linux/ptr_ring.h | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h index f175846..3a19ebd 100644 --- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h@@ -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) { - /* Allocate an extra dummy element at end of ring to avoid consumer head - * 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); + return kcalloc(size, sizeof(void *), gfp); } static inline void __ptr_ring_set_size(struct ptr_ring *r, int size)