[PATCH OLK-5.10 0/2] CVE-2025-39955
Kuniyuki Iwashima (2): tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). net/ipv4/tcp.c | 5 +++++ net/ipv4/tcp_input.c | 1 - 2 files changed, 5 insertions(+), 1 deletion(-) -- 2.9.5
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From: Kuniyuki Iwashima <kuniyu@google.com> stable inclusion from stable-v5.10.245 commit a4378dedd6e07e62f2fccb17d78c9665718763d0 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/7975 CVE: CVE-2025-39955 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 ] syzbot reported the splat below where a socket had tcp_sk(sk)->fastopen_rsk in the TCP_ESTABLISHED state. [0] syzbot reused the server-side TCP Fast Open socket as a new client before the TFO socket completes 3WHS: 1. accept() 2. connect(AF_UNSPEC) 3. connect() to another destination As of accept(), sk->sk_state is TCP_SYN_RECV, and tcp_disconnect() changes it to TCP_CLOSE and makes connect() possible, which restarts timers. Since tcp_disconnect() forgot to clear tcp_sk(sk)->fastopen_rsk, the retransmit timer triggered the warning and the intended packet was not retransmitted. Let's call reqsk_fastopen_remove() in tcp_disconnect(). [0]: WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_timer.c:542 tcp_retransmit_timer (net/ipv4/tcp_timer.c:542 (discriminator 7)) Modules linked in: CPU: 2 UID: 0 PID: 0 Comm: swapper/2 Not tainted 6.17.0-rc5-g201825fb4278 #62 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:tcp_retransmit_timer (net/ipv4/tcp_timer.c:542 (discriminator 7)) Code: 41 55 41 54 55 53 48 8b af b8 08 00 00 48 89 fb 48 85 ed 0f 84 55 01 00 00 0f b6 47 12 3c 03 74 0c 0f b6 47 12 3c 04 74 04 90 <0f> 0b 90 48 8b 85 c0 00 00 00 48 89 ef 48 8b 40 30 e8 6a 4f 06 3e RSP: 0018:ffffc900002f8d40 EFLAGS: 00010293 RAX: 0000000000000002 RBX: ffff888106911400 RCX: 0000000000000017 RDX: 0000000002517619 RSI: ffffffff83764080 RDI: ffff888106911400 RBP: ffff888106d5c000 R08: 0000000000000001 R09: ffffc900002f8de8 R10: 00000000000000c2 R11: ffffc900002f8ff8 R12: ffff888106911540 R13: ffff888106911480 R14: ffff888106911840 R15: ffffc900002f8de0 FS: 0000000000000000(0000) GS:ffff88907b768000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8044d69d90 CR3: 0000000002c30003 CR4: 0000000000370ef0 Call Trace: <IRQ> tcp_write_timer (net/ipv4/tcp_timer.c:738) call_timer_fn (kernel/time/timer.c:1747) __run_timers (kernel/time/timer.c:1799 kernel/time/timer.c:2372) timer_expire_remote (kernel/time/timer.c:2385 kernel/time/timer.c:2376 kernel/time/timer.c:2135) tmigr_handle_remote_up (kernel/time/timer_migration.c:944 kernel/time/timer_migration.c:1035) __walk_groups.isra.0 (kernel/time/timer_migration.c:533 (discriminator 1)) tmigr_handle_remote (kernel/time/timer_migration.c:1096) handle_softirqs (./arch/x86/include/asm/jump_label.h:36 ./include/trace/events/irq.h:142 kernel/softirq.c:580) irq_exit_rcu (kernel/softirq.c:614 kernel/softirq.c:453 kernel/softirq.c:680 kernel/softirq.c:696) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1050 (discriminator 35) arch/x86/kernel/apic/apic.c:1050 (discriminator 35)) </IRQ> Fixes: 8336886f786f ("tcp: TCP Fast Open Server - support TFO listeners") Reported-by: syzkaller <syzkaller@googlegroups.com> Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com> Link: https://patch.msgid.link/20250915175800.118793-2-kuniyu@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: net/ipv4/tcp.c [commit 4faeee0cf8a5 ("tcp: deny tcp_disconnect() when threads are waiting") not merged] Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> --- net/ipv4/tcp.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index e024816..f444721 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2825,6 +2825,7 @@ int tcp_disconnect(struct sock *sk, int flags) struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); int old_state = sk->sk_state; + struct request_sock *req; u32 seq; if (old_state != TCP_CLOSE) @@ -2939,6 +2940,10 @@ int tcp_disconnect(struct sock *sk, int flags) /* Clean up fastopen related fields */ + req = rcu_dereference_protected(tp->fastopen_rsk, + lockdep_sock_is_held(sk)); + if (req) + reqsk_fastopen_remove(sk, req, false); tcp_free_fastopen_req(tp); inet->defer_connect = 0; tp->fastopen_client_fail = 0; -- 2.9.5
From: Kuniyuki Iwashima <kuniyu@google.com> mainline inclusion from mainline-v6.18-rc1 commit 2e7cbbbe3d61c63606994b7ff73c72537afe2e1c category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/7975 CVE: CVE-2025-39955 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- syzbot reported the splat below in tcp_conn_request(). [0] If a listener is close()d while a TFO socket is being processed in tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk and calls inet_child_forget(), which calls tcp_disconnect() for the TFO socket. After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(), where reqsk_put() is called due to !reqsk->sk. Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the drop_and_free label causes the refcount underflow for the listener and double-free of the reqsk. Let's remove reqsk_fastopen_remove() in tcp_conn_request(). Note that other callers make sure tp->fastopen_rsk is not NULL. [0]: refcount_t: underflow; use-after-free. WARNING: CPU: 12 PID: 5563 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28) Modules linked in: CPU: 12 UID: 0 PID: 5563 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:refcount_warn_saturate (lib/refcount.c:28) Code: ab e8 8e b4 98 ff 0f 0b c3 cc cc cc cc cc 80 3d a4 e4 d6 01 00 75 9c c6 05 9b e4 d6 01 01 48 c7 c7 e8 df fb ab e8 6a b4 98 ff <0f> 0b e9 03 5b 76 00 cc 80 3d 7d e4 d6 01 00 0f 85 74 ff ff ff c6 RSP: 0018:ffffa79fc0304a98 EFLAGS: 00010246 RAX: d83af4db1c6b3900 RBX: ffff9f65c7a69020 RCX: d83af4db1c6b3900 RDX: 0000000000000000 RSI: 00000000ffff7fff RDI: ffffffffac78a280 RBP: 000000009d781b60 R08: 0000000000007fff R09: ffffffffac6ca280 R10: 0000000000017ffd R11: 0000000000000004 R12: ffff9f65c7b4f100 R13: ffff9f65c7d23c00 R14: ffff9f65c7d26000 R15: ffff9f65c7a64ef8 FS: 00007f9f962176c0(0000) GS:ffff9f65fcf00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000180 CR3: 000000000dbbe006 CR4: 0000000000372ef0 Call Trace: <IRQ> tcp_conn_request (./include/linux/refcount.h:400 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 ./include/net/sock.h:1965 ./include/net/request_sock.h:131 net/ipv4/tcp_input.c:7301) tcp_rcv_state_process (net/ipv4/tcp_input.c:6708) tcp_v6_do_rcv (net/ipv6/tcp_ipv6.c:1670) tcp_v6_rcv (net/ipv6/tcp_ipv6.c:1906) ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:438) ip6_input (net/ipv6/ip6_input.c:500) ipv6_rcv (net/ipv6/ip6_input.c:311) __netif_receive_skb (net/core/dev.c:6104) process_backlog (net/core/dev.c:6456) __napi_poll (net/core/dev.c:7506) net_rx_action (net/core/dev.c:7569 net/core/dev.c:7696) handle_softirqs (kernel/softirq.c:579) do_softirq (kernel/softirq.c:480) </IRQ> Fixes: 45c8a6cc2bcd ("tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect().") Reported-by: syzkaller <syzkaller@googlegroups.com> Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com> Link: https://patch.msgid.link/20251001233755.1340927-1-kuniyu@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> --- net/ipv4/tcp_input.c | 1 - 1 file changed, 1 deletion(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 0c783f8..a7ceff6 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6983,7 +6983,6 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, &foc, TCP_SYNACK_FASTOPEN, skb); /* Add the child socket directly into the accept queue */ if (!inet_csk_reqsk_queue_add(sk, req, fastopen_sk)) { - reqsk_fastopen_remove(fastopen_sk, req, false); bh_unlock_sock(fastopen_sk); sock_put(fastopen_sk); goto drop_and_free; -- 2.9.5
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