UBUNTU-CVE-2024-53176
In the Linux kernel, the following vulnerability has been resolved: smb: During unmount, ensure all cached dir instances drop their dentry The unmount process (cifs_kill_sb() calling close_all_cached_dirs()) can race with various cached directory operations, which ultimately results in dentries not being dropped and these kernel BUGs: BUG: Dentry ffff88814f37e358{i=1000000000080,n=/} still in use (2) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) ------------[ cut here ]------------ kernel BUG at fs/super.c:661! This happens when a cfid is in the process of being cleaned up when, and has been removed from the cfids->entries list, including: - Receiving a lease break from the server - Server reconnection triggers invalidate_all_cached_dirs(), which removes all the cfids from the list - The laundromat thread decides to expire an old cfid. To solve these problems, dropping the dentry is done in queued work done in a newly-added cfid_put_wq workqueue, and close_all_cached_dirs() flushes that workqueue after it drops all the dentries of which it's aware. This is a global workqueue (rather than scoped to a mount), but the queued work is minimal. The final cleanup work for cleaning up a cfid is performed via work queued in the serverclose_wq workqueue; this is done separate from dropping the dentries so that close_all_cached_dirs() doesn't block on any server operations. Both of these queued works expect to invoked with a cfid reference and a tcon reference to avoid those objects from being freed while the work is ongoing. While we're here, add proper locking to close_all_cached_dirs(), and locking around the freeing of cfid->dentry.
02 / AFFECTED SOFTWARE
Affected packages
16 explicit affected versions
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91 explicit affected versions
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79 explicit affected versions
13 explicit affected versions
43 explicit affected versions
77 explicit affected versions
119 explicit affected versions
10 explicit affected versions
8 explicit affected versions
19 explicit affected versions
88 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
11 explicit affected versions
1 explicit affected versions
69 explicit affected versions
123 explicit affected versions
14 explicit affected versions
80 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: smb: During unmount, ensure all cached dir instances drop their dentry The unmount process (cifs_kill_sb() calling close_all_cached_dirs()) can race with various cached directory operations, which ultimately results in dentries not being dropped and these kernel BUGs: BUG: Dentry ffff88814f37e358{i=1000000000080,n=/} still in use (2) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) ------------[ cut here ]------------ kernel BUG at fs/super.c:661! This happens when a cfid is in the process of being cleaned up when, and has been removed from the cfids->entries list, including: - Receiving a lease break from the server - Server reconnection triggers invalidate_all_cached_dirs(), which removes all the cfids from the list - The laundromat thread decides to expire an old cfid. To solve these problems, dropping the dentry is done in queued work done in a newly-added cfid_put_wq workqueue, and close_all_cached_dirs() flushes that workqueue after it drops all the dentries of which it's aware. This is a global workqueue (rather than scoped to a mount), but the queued work is minimal. The final cleanup work for cleaning up a cfid is performed via work queued in the serverclose_wq workqueue; this is done separate from dropping the dentries so that close_all_cached_dirs() doesn't block on any server operations. Both of these queued works expect to invoked with a cfid reference and a tcon reference to avoid those objects from being freed while the work is ongoing. While we're here, add proper locking to close_all_cached_dirs(), and locking around the freeing of cfid->dentry.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/3fa640d035e5ae526769615c35cb9ed4be6e3662
- https://git.kernel.org/stable/c/3fa640d035e5ae526769615c35cb9ed4be6e3662
- https://git.kernel.org/stable/c/548812afd96982a76a93ba76c0582ea670c40d9e
- https://git.kernel.org/stable/c/73934e535cffbda1490fa97d82690a0f9aa73e94
- https://git.kernel.org/stable/c/ff4528bbc82d0d90073751f7b49e7b9e9c7e5638
- https://ubuntu.com/security/CVE-2024-53176
- https://ubuntu.com/security/notices/USN-7276-1
- https://ubuntu.com/security/notices/USN-7277-1
- https://ubuntu.com/security/notices/USN-7310-1
- https://ubuntu.com/security/notices/USN-7449-1
- https://ubuntu.com/security/notices/USN-7449-2
- https://ubuntu.com/security/notices/USN-7450-1
- https://ubuntu.com/security/notices/USN-7451-1
- https://ubuntu.com/security/notices/USN-7452-1
- https://ubuntu.com/security/notices/USN-7453-1
- https://ubuntu.com/security/notices/USN-7468-1
- https://ubuntu.com/security/notices/USN-7523-1
- https://ubuntu.com/security/notices/USN-7524-1
- https://www.cve.org/CVERecord?id=CVE-2024-53176