4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit aff6db454599d62191aabc208930e891748e4322 ]
__ptr_ring_swap_queue() tries to move pointers from the old ring to the new one, but it forgets to check if ->producer is beyond the new size at the end of the operation. This leads to an out-of-bound access in __ptr_ring_produce() as reported by syzbot.
Reported-by: syzbot+8993c0fa96d57c399735@syzkaller.appspotmail.com Fixes: 5d49de532002 ("ptr_ring: resize support") Cc: "Michael S. Tsirkin" mst@redhat.com Cc: John Fastabend john.fastabend@gmail.com Cc: Jason Wang jasowang@redhat.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Acked-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/ptr_ring.h | 2 ++ 1 file changed, 2 insertions(+)
--- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h @@ -573,6 +573,8 @@ static inline void **__ptr_ring_swap_que else if (destroy) destroy(ptr);
+ if (producer >= size) + producer = 0; __ptr_ring_set_size(r, size); r->producer = producer; r->consumer_head = 0;