CVE-2022-49018

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

mptcp: fix sleep in atomic at close time

Matt reported a splat at msk close time:

BUG: sleeping function called from invalid context at net/mptcp/protocol.c:2877
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 155, name: packetdrill
preempt_count: 201, expected: 0
RCU nest depth: 0, expected: 0
4 locks held by packetdrill/155:
#0: ffff888001536990 (&sb->s_type->i_mutex_key#6){+.+.}-{3:3}, at: __sock_release (net/socket.c:650)
#1: ffff88800b498130 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close (net/mptcp/protocol.c:2973)
#2: ffff88800b49a130 (sk_lock-AF_INET/1){+.+.}-{0:0}, at: __mptcp_close_ssk (net/mptcp/protocol.c:2363)
#3: ffff88800b49a0b0 (slock-AF_INET){+...}-{2:2}, at: __lock_sock_fast (include/net/sock.h:1820)
Preemption disabled at:
0x0
CPU: 1 PID: 155 Comm: packetdrill Not tainted 6.1.0-rc5 #365
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:107 (discriminator 4))
__might_resched.cold (kernel/sched/core.c:9891)
__mptcp_destroy_sock (include/linux/kernel.h:110)
__mptcp_close (net/mptcp/protocol.c:2959)
mptcp_subflow_queue_clean (include/net/sock.h:1777)
__mptcp_close_ssk (net/mptcp/protocol.c:2363)
mptcp_destroy_common (net/mptcp/protocol.c:3170)
mptcp_destroy (include/net/sock.h:1495)
__mptcp_destroy_sock (net/mptcp/protocol.c:2886)
__mptcp_close (net/mptcp/protocol.c:2959)
mptcp_close (net/mptcp/protocol.c:2974)
inet_release (net/ipv4/af_inet.c:432)
__sock_release (net/socket.c:651)
sock_close (net/socket.c:1367)
__fput (fs/file_table.c:320)
task_work_run (kernel/task_work.c:181 (discriminator 1))
exit_to_user_mode_prepare (include/linux/resume_user_mode.h:49)
syscall_exit_to_user_mode (kernel/entry/common.c:130)
do_syscall_64 (arch/x86/entry/common.c:87)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)

We cant call mptcp_close under the fast socket lock variant, replace it with a sock_lock_nested() as the relevant code is already under the listening msk socket lock protection.

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/b4f166651d03b5484fa179817ba8ad4899a5a6ac
• https://git.kernel.org/stable/c/d8e6c5500dbf0f3e87aace90d4beba6ae928e866