CVE-2026-45949 (GCVE-0-2026-45949)
Vulnerability from cvelistv5
Published
2026-05-27 12:18
Modified
2026-10-30 12:25
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
hwrng: core - use RCU and work_struct to fix race condition
Currently, hwrng_fill is not cleared until the hwrng_fillfn() thread
exits. Since hwrng_unregister() reads hwrng_fill outside the rng_mutex
lock, a concurrent hwrng_unregister() may call kthread_stop() again on
the same task.
Additionally, if hwrng_unregister() is called immediately after
hwrng_register(), the stopped thread may have never been executed. Thus,
hwrng_fill remains dirty even after hwrng_unregister() returns. In this
case, subsequent calls to hwrng_register() will fail to start new
threads, and hwrng_unregister() will call kthread_stop() on the same
freed task. In both cases, a use-after-free occurs:
refcount_t: addition on 0; use-after-free.
WARNING: ... at lib/refcount.c:25 refcount_warn_saturate+0xec/0x1c0
Call Trace:
kthread_stop+0x181/0x360
hwrng_unregister+0x288/0x380
virtrng_remove+0xe3/0x200
This patch fixes the race by protecting the global hwrng_fill pointer
inside the rng_mutex lock, so that hwrng_fillfn() thread is stopped only
once, and calls to kthread_run() and kthread_stop() are serialized
with the lock held.
To avoid deadlock in hwrng_fillfn() while being stopped with the lock
held, we convert current_rng to RCU, so that get_current_rng() can read
current_rng without holding the lock. To remove the lock from put_rng(),
we also delay the actual cleanup into a work_struct.
Since get_current_rng() no longer returns ERR_PTR values, the IS_ERR()
checks are removed from its callers.
With hwrng_fill protected by the rng_mutex lock, hwrng_fillfn() can no
longer clear hwrng_fill itself. Therefore, if hwrng_fillfn() returns
directly after current_rng is dropped, kthread_stop() would be called on
a freed task_struct later. To fix this, hwrng_fillfn() calls schedule()
now to keep the task alive until being stopped. The kthread_stop() call
is also moved from hwrng_unregister() to drop_current_rng(), ensuring
kthread_stop() is called on all possible paths where current_rng becomes
NULL, so that the thread would not wait forever.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: be4000bc4644d027c519b6361f5ae3bbfc52c347 Version: be4000bc4644d027c519b6361f5ae3bbfc52c347 Version: be4000bc4644d027c519b6361f5ae3bbfc52c347 Version: be4000bc4644d027c519b6361f5ae3bbfc52c347 Version: be4000bc4644d027c519b6361f5ae3bbfc52c347 Version: be4000bc4644d027c519b6361f5ae3bbfc52c347 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"drivers/char/hw_random/core.c",
"include/linux/hw_random.h"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "d60bd663b746f17fc01fdc44dd01642594176344",
"status": "affected",
"version": "be4000bc4644d027c519b6361f5ae3bbfc52c347",
"versionType": "git"
},
{
"lessThan": "1cde96d5d53b9105b48617afbc4682a83db4ff04",
"status": "affected",
"version": "be4000bc4644d027c519b6361f5ae3bbfc52c347",
"versionType": "git"
},
{
"lessThan": "d5b7730f06994499632026c30e38e0317c4569e2",
"status": "affected",
"version": "be4000bc4644d027c519b6361f5ae3bbfc52c347",
"versionType": "git"
},
{
"lessThan": "dcf416eb88eafe1e3c0f920a14bdffd10bc4d259",
"status": "affected",
"version": "be4000bc4644d027c519b6361f5ae3bbfc52c347",
"versionType": "git"
},
{
"lessThan": "ad38f2cdfef9a2f2899c30cad269baec5bfd4a5d",
"status": "affected",
"version": "be4000bc4644d027c519b6361f5ae3bbfc52c347",
"versionType": "git"
},
{
"lessThan": "cc2f39d6ac48e6e3cb2d6240bc0d6df839dd0828",
"status": "affected",
"version": "be4000bc4644d027c519b6361f5ae3bbfc52c347",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"drivers/char/hw_random/core.c",
"include/linux/hw_random.h"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.17"
},
{
"lessThan": "3.17",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.191",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.75",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.14",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.191",
"versionStartIncluding": "3.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.160",
"versionStartIncluding": "3.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.75",
"versionStartIncluding": "3.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.14",
"versionStartIncluding": "3.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.4",
"versionStartIncluding": "3.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0",
"versionStartIncluding": "3.17",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nhwrng: core - use RCU and work_struct to fix race condition\n\nCurrently, hwrng_fill is not cleared until the hwrng_fillfn() thread\nexits. Since hwrng_unregister() reads hwrng_fill outside the rng_mutex\nlock, a concurrent hwrng_unregister() may call kthread_stop() again on\nthe same task.\n\nAdditionally, if hwrng_unregister() is called immediately after\nhwrng_register(), the stopped thread may have never been executed. Thus,\nhwrng_fill remains dirty even after hwrng_unregister() returns. In this\ncase, subsequent calls to hwrng_register() will fail to start new\nthreads, and hwrng_unregister() will call kthread_stop() on the same\nfreed task. In both cases, a use-after-free occurs:\n\nrefcount_t: addition on 0; use-after-free.\nWARNING: ... at lib/refcount.c:25 refcount_warn_saturate+0xec/0x1c0\nCall Trace:\n kthread_stop+0x181/0x360\n hwrng_unregister+0x288/0x380\n virtrng_remove+0xe3/0x200\n\nThis patch fixes the race by protecting the global hwrng_fill pointer\ninside the rng_mutex lock, so that hwrng_fillfn() thread is stopped only\nonce, and calls to kthread_run() and kthread_stop() are serialized\nwith the lock held.\n\nTo avoid deadlock in hwrng_fillfn() while being stopped with the lock\nheld, we convert current_rng to RCU, so that get_current_rng() can read\ncurrent_rng without holding the lock. To remove the lock from put_rng(),\nwe also delay the actual cleanup into a work_struct.\n\nSince get_current_rng() no longer returns ERR_PTR values, the IS_ERR()\nchecks are removed from its callers.\n\nWith hwrng_fill protected by the rng_mutex lock, hwrng_fillfn() can no\nlonger clear hwrng_fill itself. Therefore, if hwrng_fillfn() returns\ndirectly after current_rng is dropped, kthread_stop() would be called on\na freed task_struct later. To fix this, hwrng_fillfn() calls schedule()\nnow to keep the task alive until being stopped. The kthread_stop() call\nis also moved from hwrng_unregister() to drop_current_rng(), ensuring\nkthread_stop() is called on all possible paths where current_rng becomes\nNULL, so that the thread would not wait forever."
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:25:49.889Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/d60bd663b746f17fc01fdc44dd01642594176344"
},
{
"url": "https://git.kernel.org/stable/c/1cde96d5d53b9105b48617afbc4682a83db4ff04"
},
{
"url": "https://git.kernel.org/stable/c/d5b7730f06994499632026c30e38e0317c4569e2"
},
{
"url": "https://git.kernel.org/stable/c/dcf416eb88eafe1e3c0f920a14bdffd10bc4d259"
},
{
"url": "https://git.kernel.org/stable/c/ad38f2cdfef9a2f2899c30cad269baec5bfd4a5d"
},
{
"url": "https://git.kernel.org/stable/c/cc2f39d6ac48e6e3cb2d6240bc0d6df839dd0828"
}
],
"title": "hwrng: core - use RCU and work_struct to fix race condition",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-45949",
"datePublished": "2026-05-27T12:18:05.718Z",
"dateReserved": "2026-05-13T15:03:33.088Z",
"dateUpdated": "2026-10-30T12:25:49.889Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
Loading…
Loading…
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.
Loading…
Loading…