CVE-2026-72315 (GCVE-0-2026-72315)
Vulnerability from cvelistv5
Published
2026-08-15 05:55
Modified
2026-08-17 05:42
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix busy dentry warning on unmount after DIO
Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed
the issue in cifs where deferred close of a file led to a dentry reference
count not being released in umount, by flushing deferredclose_wq in
cifs_kill_sb() to solve it.
However, the cifs DIO path suffers from the same busy-dentry problem caused
by a delayed dentry reference-count release:
[dio] [cifsd] [close + umount]
netfs_unbuffered_write_iter_locked
...
cifs_demultiplex_thread
netfs_unbuffered_write
cifs_issue_write
netfs_wait_for_in_progress_stream [1]
...
netfs_write_subrequest_terminated
netfs_subreq_clear_in_progress
netfs_wake_collector // wake [1]
netfs_put_subrequest
netfs_put_request
queue_work(system_dfl_wq, xxx) [2]
// dio write return cifs_close
_cifsFileInfo_put
// cfile->count 2->1
--cfile->count [3]
// umount
cifs_kill_sb
kill_anon_super
// warning triggered!
shrink_dcache_for_umount [4]
[system_dfl_wq] [5]
netfs_free_request
...
_cifsFileInfo_put
// cfile->count 1->0
--cfile->count
queue_work(fileinfo_put_wq, xxx)
[fileinfo_put_wq] [6]
cifsFileInfo_put_work
cifsFileInfo_put_final
dput
If the umount path is triggered before [5], it results warning:
BUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1)
[unmount of cifs cifs]
The existing per-inode ictx->io_count wait in cifs_evict_inode() does not
help: it lives in the inode eviction path, which runs after
shrink_dcache_for_umount() has already warned about the busy dentries.
Fix it by adding a per-superblock outstanding-rreq counter that is
incremented in cifs_init_request() and decremented in cifs_free_request().
In cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach
0 - which guarantees that all cleanup_work for this sb have run and thus
all relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq.
Then drain the workqueue so the dentry refs are dropped.
This is a targeted wait, not a flush of the system-wide system_dfl_wq.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 340cea84f691c5206561bb2e0147158fe02070be Version: 340cea84f691c5206561bb2e0147158fe02070be Version: 708c276f516d27beaded7f372ac8111cee43926c Version: 0629a1a187e424373364d681b42b101894bdb548 Version: 0e4b8faaaebe3137bec5723ef2b3cb0437fb38fd Version: f655467a9973f964b267871e5fef533ad5014494 Version: 30afc6ea72cc6cf7c8d579e79b64232801c38d08 Version: 6.1.167 ≤ Version: 6.6.130 ≤ Version: 6.12.78 ≤ Version: 6.18.20 ≤ Version: 6.19.10 ≤ |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/smb/client/cifs_fs_sb.h",
"fs/smb/client/cifsfs.c",
"fs/smb/client/connect.c",
"fs/smb/client/file.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "f0eac9c3c3711f24efc2aaf12b8ec3e54a38c214",
"status": "affected",
"version": "340cea84f691c5206561bb2e0147158fe02070be",
"versionType": "git"
},
{
"lessThan": "75f5c412fa867efa0bf9b646bffe0d912109e84a",
"status": "affected",
"version": "340cea84f691c5206561bb2e0147158fe02070be",
"versionType": "git"
},
{
"status": "affected",
"version": "708c276f516d27beaded7f372ac8111cee43926c",
"versionType": "git"
},
{
"status": "affected",
"version": "0629a1a187e424373364d681b42b101894bdb548",
"versionType": "git"
},
{
"status": "affected",
"version": "0e4b8faaaebe3137bec5723ef2b3cb0437fb38fd",
"versionType": "git"
},
{
"status": "affected",
"version": "f655467a9973f964b267871e5fef533ad5014494",
"versionType": "git"
},
{
"status": "affected",
"version": "30afc6ea72cc6cf7c8d579e79b64232801c38d08",
"versionType": "git"
},
{
"lessThan": "6.2",
"status": "affected",
"version": "6.1.167",
"versionType": "semver"
},
{
"lessThan": "6.7",
"status": "affected",
"version": "6.6.130",
"versionType": "semver"
},
{
"lessThan": "6.13",
"status": "affected",
"version": "6.12.78",
"versionType": "semver"
},
{
"lessThan": "6.19",
"status": "affected",
"version": "6.18.20",
"versionType": "semver"
},
{
"lessThan": "6.20",
"status": "affected",
"version": "6.19.10",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/smb/client/cifs_fs_sb.h",
"fs/smb/client/cifsfs.c",
"fs/smb/client/connect.c",
"fs/smb/client/file.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"lessThan": "7.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.5",
"versionStartIncluding": "7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.1.167",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.6.130",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.12.78",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.18.20",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.19.10",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix busy dentry warning on unmount after DIO\n\nCommit c68337442f03 (\"cifs: Fix busy dentry used after unmounting\") fixed\nthe issue in cifs where deferred close of a file led to a dentry reference\ncount not being released in umount, by flushing deferredclose_wq in\ncifs_kill_sb() to solve it.\n\nHowever, the cifs DIO path suffers from the same busy-dentry problem caused\nby a delayed dentry reference-count release:\n\n\t[dio]\t\t\t[cifsd]\t\t\t[close + umount]\nnetfs_unbuffered_write_iter_locked\n...\n\t\t\t\tcifs_demultiplex_thread\n netfs_unbuffered_write\n cifs_issue_write\n netfs_wait_for_in_progress_stream [1]\n\t\t\t\t...\n\t\t\t\t netfs_write_subrequest_terminated\n\t\t\t\t netfs_subreq_clear_in_progress\n\t\t\t\t netfs_wake_collector // wake [1]\n\t\t\t\t netfs_put_subrequest\n netfs_put_request\n queue_work(system_dfl_wq, xxx) [2]\n // dio write return\t\t\t\t\tcifs_close\n\t\t\t\t\t\t\t _cifsFileInfo_put\n\t\t\t\t\t\t\t // cfile-\u003ecount 2-\u003e1\n\t\t\t\t\t\t\t --cfile-\u003ecount [3]\n\n\t\t\t\t\t\t\t// umount\n\t\t\t\t\t\t\tcifs_kill_sb\n\t\t\t\t\t\t\t kill_anon_super\n\t\t\t\t\t\t\t // warning triggered!\n\t\t\t\t\t\t\t shrink_dcache_for_umount [4]\n[system_dfl_wq] [5]\nnetfs_free_request\n ...\n _cifsFileInfo_put\n // cfile-\u003ecount 1-\u003e0\n --cfile-\u003ecount\n queue_work(fileinfo_put_wq, xxx)\n\n[fileinfo_put_wq] [6]\ncifsFileInfo_put_work\n cifsFileInfo_put_final\n dput\n\nIf the umount path is triggered before [5], it results warning:\nBUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1)\n[unmount of cifs cifs]\n\nThe existing per-inode ictx-\u003eio_count wait in cifs_evict_inode() does not\nhelp: it lives in the inode eviction path, which runs after\nshrink_dcache_for_umount() has already warned about the busy dentries.\n\nFix it by adding a per-superblock outstanding-rreq counter that is\nincremented in cifs_init_request() and decremented in cifs_free_request().\nIn cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach\n0 - which guarantees that all cleanup_work for this sb have run and thus\nall relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq.\nThen drain the workqueue so the dentry refs are dropped.\n\nThis is a targeted wait, not a flush of the system-wide system_dfl_wq."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The flaw is reached through local VFS syscalls (open with O_DIRECT, pwrite, close, umount) on the in-kernel CIFS/SMB3 client mount teardown path, not via remote SMB packet handling or ksmbd server code.\nAC:L - The attacker controls both sides of the race by issuing concurrent O_DIRECT writes and close/umount from separate threads, can flood system_dfl_wq to widen the cleanup delay window, and can retry until the post-pwrite/pre-cleanup_work window is hit.\nPR:L - Exploitation requires only a local user with write access to files on an already-mounted CIFS/SMB3 share; mount/umount can be performed by the same attacker with namespace capabilities or triggered by autofs lazy-unmount on shared enterprise home-directory mounts.\nUI:N - No victim interaction is required; the attacker directly drives the open/pwrite/close/umount syscall sequence in a tight loop without relying on another user to open files or perform any action.\nS:U - Impact is confined to kernel heap corruption and privilege escalation within the same host; this is not a VM escape, sandbox escape, or cross-security-authority boundary flaw.\nC:H - Delayed netfs cleanup causes cifsFileInfo_put_final() to dereference dentry, inode, and cifsInodeInfo structures after superblock teardown has begun, constituting a use-after-free that can be leveraged for arbitrary kernel memory read.\nI:H - Post-unmount cifsFileInfo_put_final() performs lock operations and list manipulation on freed kernel objects via fileinfo_put_wq, enabling heap metadata corruption and control-flow hijacking for arbitrary write or code execution.\nA:H - The race triggers WARN in shrink_dcache_for_umount during umount, and subsequent use-after-free in the deferred dentry put worker can cause kernel oops, panic, or hang."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:42:41.932Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/f0eac9c3c3711f24efc2aaf12b8ec3e54a38c214"
},
{
"url": "https://git.kernel.org/stable/c/75f5c412fa867efa0bf9b646bffe0d912109e84a"
}
],
"title": "smb: client: fix busy dentry warning on unmount after DIO",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-72315",
"datePublished": "2026-08-15T05:55:29.761Z",
"dateReserved": "2026-08-09T03:40:39.919Z",
"dateUpdated": "2026-08-17T05:42:41.932Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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