dm thin: make get_first_thin use rcu-safe list first function
In the Linux kernel, the following vulnerability has been resolved: dm thin: make get_first_thin use rcu-safe list first function The documentation in rculist.h explains the absence of list_empty_rcu() and cautions programmers against relying on a list_empty() -> list_first() sequence in RCU safe code. This is because each of these functions performs its own READ_ONCE() of the list head. This can lead to a situation where the list_empty() sees a valid list entry, but the subsequent list_first() sees a different view of list head state after a modification. In the case of dm-thin, this author had a production box crash from a GP fault in the process_deferred_bios path. This function saw a valid list head in get_first_thin() but when it subsequently dereferenced that and turned it into a thin_c, it got the inside of the struct pool, since the list was now empty and referring to itself. The kernel on which this occurred printed both a warning about a refcount_t being saturated, and a UBSAN error for an out-of-bounds cpuid access in the queued spinlock, prior to the fault itself. When the resulting kdump was examined, it was possible to see another thread patiently waiting in thin_dtr's synchronize_rcu. The thin_dtr call managed to pull the thin_c out of the active thins list (and have it be the last entry in the active_thins list) at just the wrong moment which lead to this crash. Fortunately, the fix here is straight forward. Switch get_first_thin() function to use list_first_o
CVE-2025-21664
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-21664
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "ec037fe8c0d0f6140e3d8a49c7b29cb5582160b8",
"versionType": "git"
},
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "cd30a3960433ec2db94b3689752fa3c5df44d649",
"versionType": "git"
},
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "802666a40c71a23542c43a3f87e3a2d0f4e8fe45",
"versionType": "git"
},
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "12771050b6d059eea096993bf2001da9da9fddff",
"versionType": "git"
},
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "6b305e98de0d225ccebfb225730a9f560d28ecb0",
"versionType": "git"
},
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "cbd0d5ecfa390ac29c5380200147d09c381b2ac6",
"versionType": "git"
},
{
"status": "affected",
"version": "b10ebd34cccae1b431caf1be54919aede2be7cbe",
"lessThan": "80f130bfad1dab93b95683fc39b87235682b8f72",
"versionType": "git"
}
],
"programFiles": [
"drivers/md/dm-thin.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "3.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.4.290",
"versionType": "semver",
"lessThanOrEqual": "5.4.*"
},
{
"status": "unaffected",
"version": "5.10.234",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.177",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.125",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.72",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.10",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.13",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/md/dm-thin.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-21664
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #30426 · Revision 1
- Added to Heist Feed
- Publisher date