From: Jiayuan Chen <jiayuan.chen@linux.dev> stable inclusion from stable-v6.6.157 commit 4fd2ee4ac154c204d95d8db72221446dac5af9b8 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/19376 CVE: CVE-2026-90054 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit ce2b807f42ed5e55567b8864ab72963f90779270 ] On the normal xmit path, while in urgent mode we refuse to build a multi-segment TSO packet, so every segment gets its own urg_ptr: /* tcp_write_xmit() */ limit = mss_now; if (tso_segs > 1 && !tcp_urg_mode(tp)) limit = tcp_mss_split_point(...); The retransmit path has no such guard. __tcp_retransmit_skb() builds a segs > 1 skb and hands it to the GSO layer, which only advances th->seq per segment and copies urg_ptr verbatim: /* __tcp_retransmit_skb() */ len = cur_mss * segs; /* segs > 1, no urg_mode check */ ... /* tcp_gso_segment(): bumps seq only, urg_ptr is copied */ urg_ptr is an offset from the segment's own seq, so a copied value points at a different place on each segment. The receiver rebuilds the absolute urgent seq as seg.seq + urg_ptr, so it walks a moving urgent point instead of the one OOB byte: seg1 seq 1 urg_ptr 5001 -> urgent @ 5001 (ok) seg2 seq 1001 urg_ptr 5001 -> urgent @ 6001 (wrong, +MSS) seg3 seq 2001 urg_ptr 5001 -> urgent @ 7001 (wrong, +2*MSS) The real OOB byte is never pointed at, so the receiver stops splicing it out and delivers it as normal in-band data, corrupting the stream. Guard the retransmit length like the xmit path: keep segs = 1 while in urgent mode. Fixes: 10d3be569243 ("tcp-tso: do not split TSO packets at retransmit time") Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20260826141145.67823-1-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: JiangJieHua <jiangjiehua1@huawei.com> --- net/ipv4/tcp_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 022c40469b764..5742ee246eea2 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3478,7 +3478,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) avail_wnd = cur_mss; } - len = cur_mss * segs; + len = cur_mss * (tcp_urg_mode(tp) ? 1 : segs); if (len > avail_wnd) { len = rounddown(avail_wnd, cur_mss); if (!len) -- 2.33.8