kernel/net/ipv4/tcp.c, branch linux-6.18.y

net/tcp-md5: Fix MAC comparison to be constant-time

2026-03-19T15:08:50Z

commit 46d0d6f50dab706637f4c18a470aac20a21900d3 upstream. To prevent timing attacks, MACs need to be compared in constant time. Use the appropriate helper function for this. Fixes: cfb6eeb4c860 ("[TCP]: MD5 Signature Option (RFC2385) support.") Fixes: 658ddaaf6694 ("tcp: md5: RST: getting md5 key from listener") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Link: https://patch.msgid.link/20260302203409.13388-1-ebiggers@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

net: annotate data-races around sk->sk_{data_ready,write_space}

2026-03-12T11:09:49Z

[ Upstream commit 2ef2b20cf4e04ac8a6ba68493f8780776ff84300 ] skmsg (and probably other layers) are changing these pointers while other cpus might read them concurrently. Add corresponding READ_ONCE()/WRITE_ONCE() annotations for UDP, TCP and AF_UNIX. Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") Reported-by: syzbot+87f770387a9e5dc6b79b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/699ee9fc.050a0220.1cd54b.0009.GAE@google.com/ Signed-off-by: Eric Dumazet Cc: Daniel Borkmann Cc: John Fastabend Cc: Jakub Sitnicki Cc: Willem de Bruijn Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260225131547.1085509-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: tcp_tx_timestamp() must look at the rtx queue

2026-02-26T22:59:19Z

[ Upstream commit 838eb9687691d29915797a885b861fd09353386e ] tcp_tx_timestamp() is only called at the end of tcp_sendmsg_locked() before the final tcp_push(). By the time it is called, it is possible all the copied data has been sent already (transmit queue is empty). If this is the case, use the last skb in the rtx queue. Fixes: 75c119afe14f ("tcp: implement rb-tree based retransmit queue") Signed-off-by: Eric Dumazet Reviewed-by: Jason Xing Link: https://patch.msgid.link/20260127123828.4098577-2-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: do not write to msg_get_inq in callee

2026-01-17T15:35:11Z

commit 7d11e047eda5f98514ae62507065ac961981c025 upstream. NULL pointer dereference fix. msg_get_inq is an input field from caller to callee. Don't set it in the callee, as the caller may not clear it on struct reuse. This is a kernel-internal variant of msghdr only, and the only user does reinitialize the field. So this is not critical for that reason. But it is more robust to avoid the write, and slightly simpler code. And it fixes a bug, see below. Callers set msg_get_inq to request the input queue length to be returned in msg_inq. This is equivalent to but independent from the SO_INQ request to return that same info as a cmsg (tp->recvmsg_inq). To reduce branching in the hot path the second also sets the msg_inq. That is WAI. This is a fix to commit 4d1442979e4a ("af_unix: don't post cmsg for SO_INQ unless explicitly asked for"), which fixed the inverse. Also avoid NULL pointer dereference in unix_stream_read_generic if state->msg is NULL and msg->msg_get_inq is written. A NULL state->msg can happen when splicing as of commit 2b514574f7e8 ("net: af_unix: implement splice for stream af_unix sockets"). Also collapse two branches using a bitwise or. Cc: stable@vger.kernel.org Fixes: 4d1442979e4a ("af_unix: don't post cmsg for SO_INQ unless explicitly asked for") Link: https://lore.kernel.org/netdev/willemdebruijn.kernel.24d8030f7a3de@gmail.com/ Signed-off-by: Willem de Bruijn Reviewed-by: Jens Axboe Reviewed-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260106150626.3944363-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

tcp: take care of zero tp->window_clamp in tcp_set_rcvlowat()

2025-10-06T20:08:48Z

Some applications (like selftests/net/tcp_mmap.c) call SO_RCVLOWAT on their listener, before accept(). This has an unfortunate effect on wscale selection in tcp_select_initial_window() during 3WHS. For instance, tcp_mmap was negotiating wscale 4, regardless of tcp_rmem[2] and sysctl_rmem_max. Do not change tp->window_clamp if it is zero or bigger than our computed value. Zero value is special, it allows tcp_select_initial_window() to enable autotuning. Note that SO_RCVLOWAT use on listener is probably not wise, because tp->scaling_ratio has a default value, possibly wrong. Fixes: d1361840f8c5 ("tcp: fix SO_RCVLOWAT and RCVBUF autotuning") Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Reviewed-by: Neal Cardwell Link: https://patch.msgid.link/20251003184119.2526655-1-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: move tcp_clean_acked to tcp_sock_read_tx group

2025-09-23T00:55:25Z

tp->tcp_clean_acked is fetched in tx path when snd_una is updated. This field thus belongs to tcp_sock_read_tx group. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250919204856.2977245-7-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: move tcp->rcv_tstamp to tcp_sock_write_txrx group

2025-09-23T00:55:24Z

tcp_ack() writes this field, it belongs to tcp_sock_write_txrx. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250919204856.2977245-5-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: remove CACHELINE_ASSERT_GROUP_SIZE() uses

2025-09-23T00:55:24Z

Maintaining the CACHELINE_ASSERT_GROUP_SIZE() uses for struct tcp_sock has been painful. This had little benefit, so remove them. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250919204856.2977245-4-edumazet@google.com Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2025-09-18T18:26:06Z

Cross-merge networking fixes after downstream PR (net-6.17-rc7). No conflicts. Adjacent changes: drivers/net/ethernet/mellanox/mlx5/core/en/fs.h 9536fbe10c9d ("net/mlx5e: Add PSP steering in local NIC RX") 7601a0a46216 ("net/mlx5e: Add a miss level for ipsec crypto offload") Signed-off-by: Jakub Kicinski

tcp: add datapath logic for PSP with inline key exchange

2025-09-18T10:32:06Z

Add validation points and state propagation to support PSP key exchange inline, on TCP connections. The expectation is that application will use some well established mechanism like TLS handshake to establish a secure channel over the connection and if both endpoints are PSP-capable - exchange and install PSP keys. Because the connection can existing in PSP-unsecured and PSP-secured state we need to make sure that there are no race conditions or retransmission leaks. On Tx - mark packets with the skb->decrypted bit when PSP key is at the enqueue time. Drivers should only encrypt packets with this bit set. This prevents retransmissions getting encrypted when original transmission was not. Similarly to TLS, we'll use sk->sk_validate_xmit_skb to make sure PSP skbs can't "escape" via a PSP-unaware device without being encrypted. On Rx - validation is done under socket lock. This moves the validation point later than xfrm, for example. Please see the documentation patch for more details on the flow of securing a connection, but for the purpose of this patch what's important is that we want to enforce the invariant that once connection is secured any skb in the receive queue has been encrypted with PSP. Add GRO and coalescing checks to prevent PSP authenticated data from being combined with cleartext data, or data with non-matching PSP state. On Rx, check skb's with psp_skb_coalesce_diff() at points before psp_sk_rx_policy_check(). After skb's are policy checked and on the socket receive queue, skb_cmp_decrypted() is sufficient for checking for coalescable PSP state. On Tx, tcp_write_collapse_fence() should be called when transitioning a socket into PSP Tx state to prevent data sent as cleartext from being coalesced with PSP encapsulated data. This change only adds the validation points, for ease of review. Subsequent change will add the ability to install keys, and flesh the enforcement logic out Reviewed-by: Willem de Bruijn Signed-off-by: Jakub Kicinski Co-developed-by: Daniel Zahka Signed-off-by: Daniel Zahka Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250917000954.859376-5-daniel.zahka@gmail.com Signed-off-by: Paolo Abeni