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
