From: Tom Parkin <tparkin@katalix.com> stable inclusion from stable-v4.19.308 commit 4c3ce64bc9d36ca9164dd6c77ff144c121011aae category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I970CO Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 359e54a93ab43d32ee1bff3c2f9f10cb9f6b6e79 upstream. l2tp_ip6_sendmsg needs to avoid accounting for the transport header twice when splicing more data into an already partially-occupied skbuff. To manage this, we check whether the skbuff contains data using skb_queue_empty when deciding how much data to append using ip6_append_data. However, the code which performed the calculation was incorrect: ulen = len + skb_queue_empty(&sk->sk_write_queue) ? transhdrlen : 0; ...due to C operator precedence, this ends up setting ulen to transhdrlen for messages with a non-zero length, which results in corrupted packets on the wire. Add parentheses to correct the calculation in line with the original intent. Fixes: 9d4c75800f61 ("ipv4, ipv6: Fix handling of transhdrlen in __ip{,6}_append_data()") Cc: David Howells <dhowells@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Tom Parkin <tparkin@katalix.com> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://lore.kernel.org/r/20240220122156.43131-1-tparkin@katalix.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com> --- net/l2tp/l2tp_ip6.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c index b7b172029b2c..2f03f6a0d520 100644 --- a/net/l2tp/l2tp_ip6.c +++ b/net/l2tp/l2tp_ip6.c @@ -649,7 +649,7 @@ static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) back_from_confirm: lock_sock(sk); - ulen = len + skb_queue_empty(&sk->sk_write_queue) ? transhdrlen : 0; + ulen = len + (skb_queue_empty(&sk->sk_write_queue) ? transhdrlen : 0); err = ip6_append_data(sk, ip_generic_getfrag, msg, ulen, transhdrlen, &ipc6, &fl6, (struct rt6_info *)dst, -- 2.34.1