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Message-ID: <20240926075646.15592-1-lena.wang@mediatek.com>
Date: Thu, 26 Sep 2024 15:56:38 +0800
From: Lena Wang <lena.wang@...iatek.com>
To: <edumazet@...gle.com>, <davem@...emloft.net>, <dsahern@...nel.org>,
<pabeni@...hat.com>, <kuba@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>, Lena Wang
<lena.wang@...iatek.com>
Subject: [PATCH net] tcp: check if skb is true to avoid crash
A kernel NULL pointer dereference reported.
Backtrace:
vmlinux tcp_can_coalesce_send_queue_head(sk=0xFFFFFF80316D9400, len=755)
+ 28 </alps/OfficialRelease/Of/alps/kernel-6.6/net/ipv4/tcp_output.c:2315>
vmlinux tcp_mtu_probe(sk=0xFFFFFF80316D9400) + 3196
</alps/OfficialRelease/Of/alps/kernel-6.6/net/ipv4/tcp_output.c:2452>
vmlinux tcp_write_xmit(sk=0xFFFFFF80316D9400, mss_now=128,
nonagle=-2145862684, push_one=0, gfp=2080) + 3296
</alps/OfficialRelease/Of/alps/kernel-6.6/net/ipv4/tcp_output.c:2689>
vmlinux tcp_tsq_write() + 172
</alps/OfficialRelease/Of/alps/kernel-6.6/net/ipv4/tcp_output.c:1033>
vmlinux tcp_tsq_handler() + 104
</alps/OfficialRelease/Of/alps/kernel-6.6/net/ipv4/tcp_output.c:1042>
vmlinux tcp_tasklet_func() + 208
When there is no pending skb in sk->sk_write_queue, tcp_send_head
returns NULL. Directly dereference of skb->len will result crash.
So it is necessary to evaluate the skb to be true here.
Fixes: 808cf9e38cd7 ("tcp: Honor the eor bit in tcp_mtu_probe")
Signed-off-by: Lena Wang <lena.wang@...iatek.com>
---
net/ipv4/tcp_output.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4fd746bd4d54..12cde5d879c5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2338,17 +2338,19 @@ static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
struct sk_buff *skb, *next;
skb = tcp_send_head(sk);
- tcp_for_write_queue_from_safe(skb, next, sk) {
- if (len <= skb->len)
- break;
+ if (skb) {
+ tcp_for_write_queue_from_safe(skb, next, sk) {
+ if (len <= skb->len)
+ break;
- if (unlikely(TCP_SKB_CB(skb)->eor) ||
- tcp_has_tx_tstamp(skb) ||
- !skb_pure_zcopy_same(skb, next) ||
- skb_frags_readable(skb) != skb_frags_readable(next))
- return false;
+ if (unlikely(TCP_SKB_CB(skb)->eor) ||
+ tcp_has_tx_tstamp(skb) ||
+ !skb_pure_zcopy_same(skb, next) ||
+ skb_frags_readable(skb) != skb_frags_readable(next))
+ return false;
- len -= skb->len;
+ len -= skb->len;
+ }
}
return true;
--
2.45.2
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