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authorEric Dumazet <edumazet@google.com>2021-01-19 19:49:00 +0300
committerJakub Kicinski <kuba@kernel.org>2021-01-20 04:57:59 +0300
commitb160c28548bc0a87cbd16d5af6d3edcfd70b8c9a (patch)
tree0e0da53f6dc8add3a37b6db8b35b2180e82cb416 /net
parentfd23d2dc180fccfad4b27a8e52ba1bc415d18509 (diff)
downloadlinux-b160c28548bc0a87cbd16d5af6d3edcfd70b8c9a.tar.xz
tcp: do not mess with cloned skbs in tcp_add_backlog()
Heiner Kallweit reported that some skbs were sent with the following invalid GSO properties : - gso_size > 0 - gso_type == 0 This was triggerring a WARN_ON_ONCE() in rtl8169_tso_csum_v2. Juerg Haefliger was able to reproduce a similar issue using a lan78xx NIC and a workload mixing TCP incoming traffic and forwarded packets. The problem is that tcp_add_backlog() is writing over gso_segs and gso_size even if the incoming packet will not be coalesced to the backlog tail packet. While skb_try_coalesce() would bail out if tail packet is cloned, this overwriting would lead to corruptions of other packets cooked by lan78xx, sharing a common super-packet. The strategy used by lan78xx is to use a big skb, and split it into all received packets using skb_clone() to avoid copies. The drawback of this strategy is that all the small skb share a common struct skb_shared_info. This patch rewrites TCP gso_size/gso_segs handling to only happen on the tail skb, since skb_try_coalesce() made sure it was not cloned. Fixes: 4f693b55c3d2 ("tcp: implement coalescing on backlog queue") Signed-off-by: Eric Dumazet <edumazet@google.com> Bisected-by: Juerg Haefliger <juergh@canonical.com> Tested-by: Juerg Haefliger <juergh@canonical.com> Reported-by: Heiner Kallweit <hkallweit1@gmail.com> Link: https://bugzilla.kernel.org/show_bug.cgi?id=209423 Link: https://lore.kernel.org/r/20210119164900.766957-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_ipv4.c25
1 files changed, 13 insertions, 12 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 58207c7769d0..4e82745d336f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1760,6 +1760,7 @@ int tcp_v4_early_demux(struct sk_buff *skb)
bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
{
u32 limit = READ_ONCE(sk->sk_rcvbuf) + READ_ONCE(sk->sk_sndbuf);
+ u32 tail_gso_size, tail_gso_segs;
struct skb_shared_info *shinfo;
const struct tcphdr *th;
struct tcphdr *thtail;
@@ -1767,6 +1768,7 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
unsigned int hdrlen;
bool fragstolen;
u32 gso_segs;
+ u32 gso_size;
int delta;
/* In case all data was pulled from skb frags (in __pskb_pull_tail()),
@@ -1792,13 +1794,6 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
*/
th = (const struct tcphdr *)skb->data;
hdrlen = th->doff * 4;
- shinfo = skb_shinfo(skb);
-
- if (!shinfo->gso_size)
- shinfo->gso_size = skb->len - hdrlen;
-
- if (!shinfo->gso_segs)
- shinfo->gso_segs = 1;
tail = sk->sk_backlog.tail;
if (!tail)
@@ -1821,6 +1816,15 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
goto no_coalesce;
__skb_pull(skb, hdrlen);
+
+ shinfo = skb_shinfo(skb);
+ gso_size = shinfo->gso_size ?: skb->len;
+ gso_segs = shinfo->gso_segs ?: 1;
+
+ shinfo = skb_shinfo(tail);
+ tail_gso_size = shinfo->gso_size ?: (tail->len - hdrlen);
+ tail_gso_segs = shinfo->gso_segs ?: 1;
+
if (skb_try_coalesce(tail, skb, &fragstolen, &delta)) {
TCP_SKB_CB(tail)->end_seq = TCP_SKB_CB(skb)->end_seq;
@@ -1847,11 +1851,8 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
}
/* Not as strict as GRO. We only need to carry mss max value */
- skb_shinfo(tail)->gso_size = max(shinfo->gso_size,
- skb_shinfo(tail)->gso_size);
-
- gso_segs = skb_shinfo(tail)->gso_segs + shinfo->gso_segs;
- skb_shinfo(tail)->gso_segs = min_t(u32, gso_segs, 0xFFFF);
+ shinfo->gso_size = max(gso_size, tail_gso_size);
+ shinfo->gso_segs = min_t(u32, gso_segs + tail_gso_segs, 0xFFFF);
sk->sk_backlog.len += delta;
__NET_INC_STATS(sock_net(sk),