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authorWillem de Bruijn <willemb@google.com>2019-05-30 22:01:21 (GMT)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-04 05:59:45 (GMT)
commit8778dcee3f54acd4e082f36a4eafdcd39bce97ec (patch)
treee7fdd92bdb7f2c862c7f45707ffa1f88935fdd6e
parentbf24dc2b158e6a7f3f8424d0d1d33a4bdaffa425 (diff)
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net: correct zerocopy refcnt with udp MSG_MORE
[ Upstream commit 100f6d8e09905c59be45b6316f8f369c0be1b2d8 ] TCP zerocopy takes a uarg reference for every skb, plus one for the tcp_sendmsg_locked datapath temporarily, to avoid reaching refcnt zero as it builds, sends and frees skbs inside its inner loop. UDP and RAW zerocopy do not send inside the inner loop so do not need the extra sock_zerocopy_get + sock_zerocopy_put pair. Commit 52900d22288ed ("udp: elide zerocopy operation in hot path") introduced extra_uref to pass the initial reference taken in sock_zerocopy_alloc to the first generated skb. But, sock_zerocopy_realloc takes this extra reference at the start of every call. With MSG_MORE, no new skb may be generated to attach the extra_uref to, so refcnt is incorrectly 2 with only one skb. Do not take the extra ref if uarg && !tcp, which implies MSG_MORE. Update extra_uref accordingly. This conditional assignment triggers a false positive may be used uninitialized warning, so have to initialize extra_uref at define. Changes v1->v2: fix typo in Fixes SHA1 Fixes: 52900d22288e7 ("udp: elide zerocopy operation in hot path") Reported-by: syzbot <syzkaller@googlegroups.com> Diagnosed-by: Eric Dumazet <edumazet@google.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>
-rw-r--r--net/core/skbuff.c6
-rw-r--r--net/ipv4/ip_output.c4
-rw-r--r--net/ipv6/ip6_output.c4
3 files changed, 9 insertions, 5 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 40796b8..e5bfd42 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1001,7 +1001,11 @@ struct ubuf_info *sock_zerocopy_realloc(struct sock *sk, size_t size,
uarg->len++;
uarg->bytelen = bytelen;
atomic_set(&sk->sk_zckey, ++next);
- sock_zerocopy_get(uarg);
+
+ /* no extra ref when appending to datagram (MSG_MORE) */
+ if (sk->sk_type == SOCK_STREAM)
+ sock_zerocopy_get(uarg);
+
return uarg;
}
}
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index e8bb2e8..ac77094 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -883,7 +883,7 @@ static int __ip_append_data(struct sock *sk,
int csummode = CHECKSUM_NONE;
struct rtable *rt = (struct rtable *)cork->dst;
unsigned int wmem_alloc_delta = 0;
- bool paged, extra_uref;
+ bool paged, extra_uref = false;
u32 tskey = 0;
skb = skb_peek_tail(queue);
@@ -923,7 +923,7 @@ static int __ip_append_data(struct sock *sk,
uarg = sock_zerocopy_realloc(sk, length, skb_zcopy(skb));
if (!uarg)
return -ENOBUFS;
- extra_uref = true;
+ extra_uref = !skb; /* only extra ref if !MSG_MORE */
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 e51f3c6..b5e0c85 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1275,7 +1275,7 @@ static int __ip6_append_data(struct sock *sk,
int csummode = CHECKSUM_NONE;
unsigned int maxnonfragsize, headersize;
unsigned int wmem_alloc_delta = 0;
- bool paged, extra_uref;
+ bool paged, extra_uref = false;
skb = skb_peek_tail(queue);
if (!skb) {
@@ -1344,7 +1344,7 @@ emsgsize:
uarg = sock_zerocopy_realloc(sk, length, skb_zcopy(skb));
if (!uarg)
return -ENOBUFS;
- extra_uref = true;
+ extra_uref = !skb; /* only extra ref if !MSG_MORE */
if (rt->dst.dev->features & NETIF_F_SG &&
csummode == CHECKSUM_PARTIAL) {
paged = true;