In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix TCP timers deadlock after rmmod
Commit ef7134c7fc48 ("smb: client: Fix use-after-free of network namespace.")
fixed a netns UAF by manually enabled socket refcounting
(sk->sk_net_refcnt=1 and sock_inuse_add(net, 1)).
The reason the patch worked for that bug was because we now hold
references to the netns (get_net_track() gets a ref internally)
and they're properly released (internally, on __sk_destruct()),
but only because sk->sk_net_refcnt was set.
Problem:
(this happens regardless of CONFIG_NET_NS_REFCNT_TRACKER and regardless
if init_net or other)
Setting sk->sk_net_refcnt=1 *manually* and *after* socket creation is not
only out of cifs scope, but also technically wrong -- it's set conditionally
based on user (=1) vs kernel (=0) sockets. And net/ implementations
seem to base their user vs kernel space operations on it.
e.g. upon TCP socket close, the TCP timers are not cleared because
sk->sk_net_refcnt=1:
(cf. commit 151c9c724d05 ("tcp: properly terminate timers for kernel sockets"))
net/ipv4/tcp.c:
void tcp_close(struct sock *sk, long timeout)
{
lock_sock(sk);
__tcp_close(sk, timeout);
release_sock(sk);
if (!sk->sk_net_refcnt)
inet_csk_clear_xmit_timers_sync(sk);
sock_put(sk);
}
Which will throw a lockdep warning and then, as expected, deadlock on
tcp_write_timer().
A way to reproduce this is by running the reproducer from ef7134c7fc48
and then 'rmmod cifs'. A few seconds later, the deadlock/lockdep
warning shows up.
Fix:
We shouldn't mess with socket internals ourselves, so do not set
sk_net_refcnt manually.
Also change __sock_create() to sock_create_kern() for explicitness.
As for non-init_net network namespaces, we deal with it the best way
we can -- hold an extra netns reference for server->ssocket and drop it
when it's released. This ensures that the netns still exists whenever
we need to create/destroy server->ssocket, but is not directly tied to
it.
Metrics
Affected Vendors & Products
No data.
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References
History
Tue, 14 Jan 2025 08:45:00 +0000
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threat_severity
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cvssV3_1
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Sat, 11 Jan 2025 12:45:00 +0000
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| Description | In the Linux kernel, the following vulnerability has been resolved: smb: client: fix TCP timers deadlock after rmmod Commit ef7134c7fc48 ("smb: client: Fix use-after-free of network namespace.") fixed a netns UAF by manually enabled socket refcounting (sk->sk_net_refcnt=1 and sock_inuse_add(net, 1)). The reason the patch worked for that bug was because we now hold references to the netns (get_net_track() gets a ref internally) and they're properly released (internally, on __sk_destruct()), but only because sk->sk_net_refcnt was set. Problem: (this happens regardless of CONFIG_NET_NS_REFCNT_TRACKER and regardless if init_net or other) Setting sk->sk_net_refcnt=1 *manually* and *after* socket creation is not only out of cifs scope, but also technically wrong -- it's set conditionally based on user (=1) vs kernel (=0) sockets. And net/ implementations seem to base their user vs kernel space operations on it. e.g. upon TCP socket close, the TCP timers are not cleared because sk->sk_net_refcnt=1: (cf. commit 151c9c724d05 ("tcp: properly terminate timers for kernel sockets")) net/ipv4/tcp.c: void tcp_close(struct sock *sk, long timeout) { lock_sock(sk); __tcp_close(sk, timeout); release_sock(sk); if (!sk->sk_net_refcnt) inet_csk_clear_xmit_timers_sync(sk); sock_put(sk); } Which will throw a lockdep warning and then, as expected, deadlock on tcp_write_timer(). A way to reproduce this is by running the reproducer from ef7134c7fc48 and then 'rmmod cifs'. A few seconds later, the deadlock/lockdep warning shows up. Fix: We shouldn't mess with socket internals ourselves, so do not set sk_net_refcnt manually. Also change __sock_create() to sock_create_kern() for explicitness. As for non-init_net network namespaces, we deal with it the best way we can -- hold an extra netns reference for server->ssocket and drop it when it's released. This ensures that the netns still exists whenever we need to create/destroy server->ssocket, but is not directly tied to it. | |
| Title | smb: client: fix TCP timers deadlock after rmmod | |
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2025-01-11T12:35:43.170Z
Updated: 2025-01-11T12:35:43.170Z
Reserved: 2025-01-11T12:33:33.715Z
Link: CVE-2024-54680
Vulnrichment
No data.
NVD
Status : Received
Published: 2025-01-11T13:15:27.340
Modified: 2025-01-11T13:15:27.340
Link: CVE-2024-54680
Redhat