| 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-2024-53176: smb: During unmount, ensure all cached dir instances drop their dentry |
| |
| Description |
| =========== |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2024-53176 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.1 with commit ebe98f1447bbccf8228335c62d86af02a0ed23f7 and fixed in 6.6.64 with commit 73934e535cffbda1490fa97d82690a0f9aa73e94 |
| Issue introduced in 6.1 with commit ebe98f1447bbccf8228335c62d86af02a0ed23f7 and fixed in 6.11.11 with commit ff4528bbc82d0d90073751f7b49e7b9e9c7e5638 |
| Issue introduced in 6.1 with commit ebe98f1447bbccf8228335c62d86af02a0ed23f7 and fixed in 6.12.2 with commit 548812afd96982a76a93ba76c0582ea670c40d9e |
| Issue introduced in 6.1 with commit ebe98f1447bbccf8228335c62d86af02a0ed23f7 and fixed in 6.13 with commit 3fa640d035e5ae526769615c35cb9ed4be6e3662 |
| |
| 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-2024-53176 |
| 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/cached_dir.c |
| fs/smb/client/cached_dir.h |
| fs/smb/client/cifsfs.c |
| fs/smb/client/cifsglob.h |
| fs/smb/client/inode.c |
| fs/smb/client/trace.h |
| |
| |
| 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/73934e535cffbda1490fa97d82690a0f9aa73e94 |
| https://git.kernel.org/stable/c/ff4528bbc82d0d90073751f7b49e7b9e9c7e5638 |
| https://git.kernel.org/stable/c/548812afd96982a76a93ba76c0582ea670c40d9e |
| https://git.kernel.org/stable/c/3fa640d035e5ae526769615c35cb9ed4be6e3662 |
