From: Willem de Bruijn <will...@google.com>
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 <syzkal...@googlegroups.com>
Signed-off-by: Willem de Bruijn <will...@google.com>
---
net/ipv4/ip_output.c | 2 +-
net/ipv6/ip6_output.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 8c9189a41b136..16f9159234a20 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -918,7 +918,7 @@ static int __ip_append_data(struct sock *sk,
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;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 934c88f128abb..834475717110e 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1340,7 +1340,7 @@ static int __ip6_append_data(struct sock *sk,
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;
--
2.22.0.rc2.383.gf4fbbf30c2-goog
