5.4-stable review patch. If anyone has any objections, please let me know.
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From: Tom Parkin tparkin@katalix.com
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 --- net/l2tp/l2tp_ip6.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/l2tp/l2tp_ip6.c +++ b/net/l2tp/l2tp_ip6.c @@ -644,7 +644,7 @@ static int l2tp_ip6_sendmsg(struct sock
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,