From: Willem de Bruijn willemb@google.com
[ Upstream commit 522924b583082f51b8a2406624a2f27c22119b20 ]
The below patch fixes an incorrect zerocopy refcnt increment when appending with MSG_MORE to an existing zerocopy udp skb.
send(.., MSG_ZEROCOPY | MSG_MORE); // refcnt 1 send(.., MSG_ZEROCOPY | MSG_MORE); // refcnt still 1 (bar frags)
But it missed that zerocopy need not be passed at the first send. The right test whether the uarg is newly allocated and thus has extra refcnt 1 is not !skb, but !skb_zcopy.
send(.., MSG_MORE); // <no uarg> send(.., MSG_ZEROCOPY); // refcnt 1
Fixes: 100f6d8e09905 ("net: correct zerocopy refcnt with udp MSG_MORE") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/ip_output.c | 2 +- net/ipv6/ip6_output.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
--- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -923,7 +923,7 @@ static int __ip_append_data(struct sock uarg = sock_zerocopy_realloc(sk, length, skb_zcopy(skb)); if (!uarg) return -ENOBUFS; - extra_uref = !skb; /* only extra ref if !MSG_MORE */ + extra_uref = !skb_zcopy(skb); /* only ref on new uarg */ if (rt->dst.dev->features & NETIF_F_SG && csummode == CHECKSUM_PARTIAL) { paged = true; --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1344,7 +1344,7 @@ emsgsize: uarg = sock_zerocopy_realloc(sk, length, skb_zcopy(skb)); if (!uarg) return -ENOBUFS; - extra_uref = !skb; /* only extra ref if !MSG_MORE */ + extra_uref = !skb_zcopy(skb); /* only ref on new uarg */ if (rt->dst.dev->features & NETIF_F_SG && csummode == CHECKSUM_PARTIAL) { paged = true;