Description

In the Linux kernel, the following vulnerability has been resolved: tcp: defer shutdown(SEND_SHUTDOWN) for TCP_SYN_RECV sockets TCP_SYN_RECV state is really special, it is only used by cross-syn connections, mostly used by fuzzers. In the following crash [1], syzbot managed to trigger a divide by zero in tcp_rcv_space_adjust() A socket makes the following state transitions, without ever calling tcp_init_transfer(), meaning tcp_init_buffer_space() is also not called. TCP_CLOSE connect() TCP_SYN_SENT TCP_SYN_RECV shutdown() -> tcp_shutdown(sk, SEND_SHUTDOWN) TCP_FIN_WAIT1 To fix this issue, change tcp_shutdown() to not perform a TCP_SYN_RECV -> TCP_FIN_WAIT1 transition, which makes no sense anyway. When tcp_rcv_state_process() later changes socket state from TCP_SYN_RECV to TCP_ESTABLISH, then look at sk->sk_shutdown to finally enter TCP_FIN_WAIT1 state, and send a FIN packet from a sane socket state. This means tcp_send_fin() can now be called from BH context, and must use GFP_ATOMIC allocations. [1] divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 1 PID: 5084 Comm: syz-executor358 Not tainted 6.9.0-rc6-syzkaller-00022-g98369dccd2f8 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 RIP: 0010:tcp_rcv_space_adjust+0x2df/0x890 net/ipv4/tcp_input.c:767 Code: e3 04 4c 01 eb 48 8b 44 24 38 0f b6 04 10 84 c0 49 89 d5 0f 85 a5 03 00 00 41 8b 8e c8 09 00 00 89 e8 29 c8 48 0f af c3 31 d2 <48> f7 f1 48 8d 1c 43 49 8d 96 76 08 00 00 48 89 d0 48 c1 e8 03 48 RSP: 0018:ffffc900031ef3f0 EFLAGS: 00010246 RAX: 0c677a10441f8f42 RBX: 000000004fb95e7e RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000027d4b11f R08: ffffffff89e535a4 R09: 1ffffffff25e6ab7 R10: dffffc0000000000 R11: ffffffff8135e920 R12: ffff88802a9f8d30 R13: dffffc0000000000 R14: ffff88802a9f8d00 R15: 1ffff1100553f2da FS: 00005555775c0380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1155bf2304 CR3: 000000002b9f2000 CR4: 0000000000350ef0 Call Trace: <TASK> tcp_recvmsg_locked+0x106d/0x25a0 net/ipv4/tcp.c:2513 tcp_recvmsg+0x25d/0x920 net/ipv4/tcp.c:2578 inet6_recvmsg+0x16a/0x730 net/ipv6/af_inet6.c:680 sock_recvmsg_nosec net/socket.c:1046 [inline] sock_recvmsg+0x109/0x280 net/socket.c:1068 ____sys_recvmsg+0x1db/0x470 net/socket.c:2803 ___sys_recvmsg net/socket.c:2845 [inline] do_recvmmsg+0x474/0xae0 net/socket.c:2939 __sys_recvmmsg net/socket.c:3018 [inline] __do_sys_recvmmsg net/socket.c:3041 [inline] __se_sys_recvmmsg net/socket.c:3034 [inline] __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3034 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7faeb6363db9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffcc1997168 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007faeb6363db9 RDX: 0000000000000001 RSI: 0000000020000bc0 RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000000 R09: 000000000000001c R10: 0000000000000122 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001

Metrics

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.

CVSS 4.0 Severity and Vector Strings:

NIST: NVD

N/A

NVD assessment not yet provided.

CVSS 3.x Severity and Vector Strings:

NIST: NVD

Base Score:  N/A

NVD assessment not yet provided.

ADP:  CISA-ADP

Base Score:  5.5 MEDIUM

Vector:  CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS 2.0 Severity and Vector Strings:

NIST: NVD

Base Score: N/A

NVD assessment not yet provided.

kernel.org https://www.openwall.com/lists/oss-security/2024/10/29/1 [No types assigned]

CISA-ADP AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CISA-ADP AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

kernel.org https://lists.debian.org/debian-lts-announce/2024/06/msg00019.html

kernel.org https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html

CISA-ADP AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA-ADP CWE-369

kernel.org https://lists.debian.org/debian-lts-announce/2024/06/msg00019.html [No types assigned]

kernel.org https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html [No types assigned]

In the Linux kernel, the following vulnerability has been resolved:

tcp: defer shutdown(SEND_SHUTDOWN) for TCP_SYN_RECV sockets

TCP_SYN_RECV state is really special, it is only used by
cross-syn connections, mostly used by fuzzers.

In the following crash [1], syzbot managed to trigger a divide
by zero in tcp_rcv_space_adjust()

A socket makes the following state transitions,
without ever calling tcp_init_transfer(),
meaning tcp_init_buffer_space() is also not called.

         TCP_CLOSE
conne

kernel.org https://git.kernel.org/stable/c/2552c9d9440f8e7a2ed0660911ff00f25b90a0a4 [No types assigned]

kernel.org https://git.kernel.org/stable/c/34e41a031fd7523bf1cd00a2adca2370aebea270 [No types assigned]

kernel.org https://git.kernel.org/stable/c/3fe4ef0568a48369b1891395d13ac593b1ba41b1 [No types assigned]

kernel.org https://git.kernel.org/stable/c/413c33b9f3bc36fdf719690a78824db9f88a9485 [No types assigned]

kernel.org https://git.kernel.org/stable/c/94062790aedb505bdda209b10bea47b294d6394f [No types assigned]

kernel.org https://git.kernel.org/stable/c/cbf232ba11bc86a5281b4f00e1151349ef4d45cf [No types assigned]

kernel.org https://git.kernel.org/stable/c/ed5e279b69e007ce6c0fe82a5a534c1b19783214 [No types assigned]

kernel.org https://git.kernel.org/stable/c/f47d0d32fa94e815fdd78b8b88684873e67939f4 [No types assigned]