We try to allocate one more entry for lockless peeking. The adding operation may overflow which causes zero to be passed to kmalloc(). In this case, it returns ZERO_SIZE_PTR without any notice by ptr ring. Try to do producing or consuming on such ring will lead NULL dereference. Fix this detect and fail early.
Fixes: bcecb4bbf88a ("net: ptr_ring: otherwise safe empty checks can overrun array bounds") Reported-by: syzbot+87678bcf753b44c39...@syzkaller.appspotmail.com Cc: John Fastabend <john.fastab...@gmail.com> Signed-off-by: Jason Wang <jasow...@redhat.com> --- include/linux/ptr_ring.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h index 9ca1726..3f99484 100644 --- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h @@ -453,6 +453,8 @@ 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) { + if (unlikely(size + 1 == 0)) + return NULL; /* 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 -- 2.7.4