CVE-2023-53088

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

mptcp: fix UaF in listener shutdown

As reported by Christoph after having refactored the passive

socket initialization, the mptcp listener shutdown path is prone

to an UaF issue.

BUG: KASAN: use-after-free in _raw_spin_lock_bh+0x73/0xe0

Write of size 4 at addr ffff88810cb23098 by task syz-executor731/1266

CPU: 1 PID: 1266 Comm: syz-executor731 Not tainted 6.2.0-rc59af4eaa31c1f6c00c8f1e448ed99a45c66340dd5 #6

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014

Call Trace:

<TASK>

dump_stack_lvl+0x6e/0x91

print_report+0x16a/0x46f

kasan_report+0xad/0x130

kasan_check_range+0x14a/0x1a0

_raw_spin_lock_bh+0x73/0xe0

subflow_error_report+0x6d/0x110

sk_error_report+0x3b/0x190

tcp_disconnect+0x138c/0x1aa0

inet_child_forget+0x6f/0x2e0

inet_csk_listen_stop+0x209/0x1060

__mptcp_close_ssk+0x52d/0x610

mptcp_destroy_common+0x165/0x640

mptcp_destroy+0x13/0x80

__mptcp_destroy_sock+0xe7/0x270

__mptcp_close+0x70e/0x9b0

mptcp_close+0x2b/0x150

inet_release+0xe9/0x1f0

__sock_release+0xd2/0x280

sock_close+0x15/0x20

__fput+0x252/0xa20

task_work_run+0x169/0x250

exit_to_user_mode_prepare+0x113/0x120

syscall_exit_to_user_mode+0x1d/0x40

do_syscall_64+0x48/0x90

entry_SYSCALL_64_after_hwframe+0x72/0xdc

The msk grace period can legitly expire in between the last

reference count dropped in mptcp_subflow_queue_clean() and

the later eventual access in inet_csk_listen_stop()

After the previous patch we don't need anymore special-casing

msk listener socket cleanup: the mptcp worker will process each

of the unaccepted msk sockets.

Just drop the now unnecessary code.

Please note this commit depends on the two parent ones:

mptcp: refactor passive socket initialization

mptcp: use the workqueue to destroy unaccepted sockets