From: Willem de Bruijn <will...@google.com>
Syzkaller hits WARN_ON(sk->sk_wmem_queued) in sk_stream_kill_queues
after triggering an EFAULT in __zerocopy_sg_from_iter.
On this error, skb_zerocopy_stream_iter resets the skb to its state
before the operation with __pskb_trim. It cannot kfree_skb like
datagram callers, as the skb may have data from a previous send call.
__pskb_trim calls skb_condense for unowned skbs, which adjusts their
truesize. These tcp skbuffs are owned and their truesize must add up
to sk_wmem_queued. But they match because their skb->sk is NULL until
tcp_transmit_skb.
Temporarily set skb->sk when calling __pskb_trim to signal that the
skbuffs are owned and avoid the skb_condense path.
Fixes: 52267790ef52 ("sock: add MSG_ZEROCOPY")
Signed-off-by: Willem de Bruijn <will...@google.com>
---
net/core/skbuff.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e62476beee95..24656076906d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1124,9 +1124,13 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct
sk_buff *skb,
err = __zerocopy_sg_from_iter(sk, skb, &msg->msg_iter, len);
if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) {
+ struct sock *save_sk = skb->sk;
+
/* Streams do not free skb on error. Reset to prev state. */
msg->msg_iter = orig_iter;
+ skb->sk = sk;
___pskb_trim(skb, orig_len);
+ skb->sk = save_sk;
return err;
}
--
2.15.0.rc1.287.g2b38de12cc-goog
