GHSA-66HG-CMFH-7HVM
Vulnerability from github – Published: 2024-12-27 15:31 – Updated: 2025-10-08 15:32In 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.
{
"affected": [],
"aliases": [
"CVE-2024-53176"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-12-27T14:15:24Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: During unmount, ensure all cached dir instances drop their dentry\n\nThe unmount process (cifs_kill_sb() calling close_all_cached_dirs()) can\nrace with various cached directory operations, which ultimately results\nin dentries not being dropped and these kernel BUGs:\n\nBUG: Dentry ffff88814f37e358{i=1000000000080,n=/} still in use (2) [unmount of cifs cifs]\nVFS: Busy inodes after unmount of cifs (cifs)\n------------[ cut here ]------------\nkernel BUG at fs/super.c:661!\n\nThis happens when a cfid is in the process of being cleaned up when, and\nhas been removed from the cfids-\u003eentries list, including:\n\n- Receiving a lease break from the server\n- Server reconnection triggers invalidate_all_cached_dirs(), which\n removes all the cfids from the list\n- The laundromat thread decides to expire an old cfid.\n\nTo solve these problems, dropping the dentry is done in queued work done\nin a newly-added cfid_put_wq workqueue, and close_all_cached_dirs()\nflushes that workqueue after it drops all the dentries of which it\u0027s\naware. This is a global workqueue (rather than scoped to a mount), but\nthe queued work is minimal.\n\nThe final cleanup work for cleaning up a cfid is performed via work\nqueued in the serverclose_wq workqueue; this is done separate from\ndropping the dentries so that close_all_cached_dirs() doesn\u0027t block on\nany server operations.\n\nBoth of these queued works expect to invoked with a cfid reference and\na tcon reference to avoid those objects from being freed while the work\nis ongoing.\n\nWhile we\u0027re here, add proper locking to close_all_cached_dirs(), and\nlocking around the freeing of cfid-\u003edentry.",
"id": "GHSA-66hg-cmfh-7hvm",
"modified": "2025-10-08T15:32:25Z",
"published": "2024-12-27T15:31:50Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-53176"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3fa640d035e5ae526769615c35cb9ed4be6e3662"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/548812afd96982a76a93ba76c0582ea670c40d9e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/73934e535cffbda1490fa97d82690a0f9aa73e94"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ff4528bbc82d0d90073751f7b49e7b9e9c7e5638"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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