| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-54680: smb: client: fix TCP timers deadlock after rmmod |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2024-54680 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.6.62 with commit e8c71494181153a134c96da28766a57bd1eac8cb and fixed in 6.6.68 with commit 906807c734ed219dcb2e7bbfde5c4168ed72a3d0 |
| Issue introduced in 6.12 with commit ef7134c7fc48e1441b398e55a862232868a6f0a7 and fixed in 6.12.7 with commit 127e907e11ccd54b59bb78fc22c43ccb76c71079 |
| Issue introduced in 6.12 with commit ef7134c7fc48e1441b398e55a862232868a6f0a7 and fixed in 6.13 with commit e9f2517a3e18a54a3943c098d2226b245d488801 |
| Issue introduced in 6.11.9 with commit c7f9282fc27fc36dbaffc8527c723de264a132f8 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-54680 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| fs/smb/client/connect.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/906807c734ed219dcb2e7bbfde5c4168ed72a3d0 |
| https://git.kernel.org/stable/c/127e907e11ccd54b59bb78fc22c43ccb76c71079 |
| https://git.kernel.org/stable/c/e9f2517a3e18a54a3943c098d2226b245d488801 |
