CVE: CVE-2021-47594
Published: 2024-06-19
Description: In the Linux kernel, the following vulnerability has been resolved:

mptcp: never allow the PM to close a listener subflow

Currently, when deleting an endpoint the netlink PM treverses
all the local MPTCP sockets, regardless of their status.

If an MPTCP listener socket is bound to the IP matching the
delete endpoint, the listener TCP socket will be closed.
That is unexpected, the PM should only affect data subflows.

Additionally, syzbot was able to trigger a NULL ptr dereference
due to the above:

general protection fault, probably for non-canonical address 0xdffffc[PII_REDACTED]: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x[PII_REDACTED]000018-0x[PII_REDACTED]00001f]
CPU: 1 PID: 6550 Comm: syz-executor122 Not tainted 5.16.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__lock_acquire+0xd7d/0x54a0 kernel/locking/lockdep.c:4897
Code: 0f 0e 41 be 01 00 00 00 0f 86 c8 00 00 00 89 05 69 cc 0f 0e e9 bd 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 0f 85 f3 2f 00 00 48 81 3b 20 75 17 8f 0f 84 52 f3 ff
RSP: 0018:ffffc90001f2f818 EFLAGS: 00010016
RAX: dffffc[PII_REDACTED] RBX: [PII_REDACTED] RCX: [PII_REDACTED]
RDX: [PII_REDACTED] RSI: [PII_REDACTED] RDI: [PII_REDACTED]
RBP: [PII_REDACTED] R08: [PII_REDACTED] R09: [PII_REDACTED]
R10: [PII_REDACTED] R11:[PII_REDACTED]00000a R12: [PII_REDACTED]
R13: ffff88801b98d700 R14: [PII_REDACTED] R15: [PII_REDACTED]
FS:  00007f177cd3d700(0000) GS:ffff8880b9d00000(0000) knlGS:[PII_REDACTED]
CS:  0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
CR2: 00007f177cd1b268 CR3: 000000001dd55000 CR4:[PII_REDACTED]350ee0
Call Trace:
 <TASK>
 lock_acquire kernel/locking/lockdep.c:5637 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
 finish_wait+0xc0/0x270 kernel/sched/wait.c:400
 inet_csk_wait_for_connect net/ipv4/inet_connection_sock.c:464 [inline]
 inet_csk_accept+0x7de/0x9d0 net/ipv4/inet_connection_sock.c:497
 mptcp_accept+0xe5/0x500 net/mptcp/protocol.c:2865
 inet_accept+0xe4/0x7b0 net/ipv4/af_inet.c:739
 mptcp_stream_accept+0x2e7/0x10e0 net/mptcp/protocol.c:3345
 do_accept+0x382/0x510 net/socket.c:1773
 __sys_accept4_file+0x7e/0xe0 net/socket.c:1816
 __sys_accept4+0xb0/0x100 net/socket.c:1846
 __do_sys_accept net/socket.c:1864 [inline]
 __se_sys_accept net/socket.c:1861 [inline]
 __x64_sys_accept+0x71/0xb0 net/socket.c:1861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f177cd8b8e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 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:00007f177cd3d308 EFLAGS: 00000246 ORIG_RAX:[PII_REDACTED]00002b
RAX: ffffffffffffffda RBX: 00007f177ce13408 RCX: 00007f177cd8b8e9
RDX: [PII_REDACTED] RSI: [PII_REDACTED] RDI: [PII_REDACTED]
RBP: 00007f177ce13400 R08: [PII_REDACTED] R09: [PII_REDACTED]
R10: [PII_REDACTED] R11: [PII_REDACTED] R12: 00007f177ce1340c
R13: 00007f177cde1004 R14: 6d705f706374706d R15: [PII_REDACTED]
 </TASK>

Fix the issue explicitly skipping MPTCP socket in TCP_LISTEN
status.
CVSS Score: 5.5 (MEDIUM)
CWE: CWE-476
References: https://git.kernel.org/stable/c/1456a0004cc54c58adb2501cb0c95dc8b3c83e9e; https://git.kernel.org/stable/c/b0cdc5dbcf2ba0d99785da5aabf1b17943805b8a; https://git.kernel.org/stable/c/1456a0004cc54c58adb2501cb0c95dc8b3c83e9e