275 lines
15 KiB
JSON
275 lines
15 KiB
JSON
{
|
||
"dataType": "CVE_RECORD",
|
||
"dataVersion": "5.2",
|
||
"cveMetadata": {
|
||
"cveId": "CVE-2021-46921",
|
||
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
|
||
"state": "PUBLISHED",
|
||
"assignerShortName": "Linux",
|
||
"dateReserved": "2024-02-25T13:45:52.719Z",
|
||
"datePublished": "2024-02-27T09:36:26.461Z",
|
||
"dateUpdated": "2026-08-05T08:45:05.258Z"
|
||
},
|
||
"containers": {
|
||
"cna": {
|
||
"providerMetadata": {
|
||
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
|
||
"shortName": "Linux",
|
||
"dateUpdated": "2026-08-05T08:45:05.258Z"
|
||
},
|
||
"descriptions": [
|
||
{
|
||
"lang": "en",
|
||
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlocking/qrwlock: Fix ordering in queued_write_lock_slowpath()\n\nWhile this code is executed with the wait_lock held, a reader can\nacquire the lock without holding wait_lock. The writer side loops\nchecking the value with the atomic_cond_read_acquire(), but only truly\nacquires the lock when the compare-and-exchange is completed\nsuccessfully which isn’t ordered. This exposes the window between the\nacquire and the cmpxchg to an A-B-A problem which allows reads\nfollowing the lock acquisition to observe values speculatively before\nthe write lock is truly acquired.\n\nWe've seen a problem in epoll where the reader does a xchg while\nholding the read lock, but the writer can see a value change out from\nunder it.\n\n Writer | Reader\n --------------------------------------------------------------------------------\n ep_scan_ready_list() |\n |- write_lock_irq() |\n |- queued_write_lock_slowpath() |\n\t|- atomic_cond_read_acquire() |\n\t\t\t\t | read_lock_irqsave(&ep->lock, flags);\n --> (observes value before unlock) | chain_epi_lockless()\n | | epi->next = xchg(&ep->ovflist, epi);\n | | read_unlock_irqrestore(&ep->lock, flags);\n | |\n | atomic_cmpxchg_relaxed() |\n |-- READ_ONCE(ep->ovflist); |\n\nA core can order the read of the ovflist ahead of the\natomic_cmpxchg_relaxed(). Switching the cmpxchg to use acquire\nsemantics addresses this issue at which point the atomic_cond_read can\nbe switched to use relaxed semantics.\n\n[peterz: use try_cmpxchg()]"
|
||
}
|
||
],
|
||
"metrics": [
|
||
{
|
||
"cvssV3_1": {
|
||
"version": "3.1",
|
||
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
|
||
"baseScore": 7.8,
|
||
"baseSeverity": "HIGH"
|
||
},
|
||
"scenarios": [
|
||
{
|
||
"lang": "en",
|
||
"value": "AV:L - The bug is in queued_write_lock_slowpath() for rwlock_t; the demonstrated path is local epoll_wait → ep_send_events → ep_done_scan → write_lock_irq(), which requires local syscall access rather than network or physical reachability.\nAC:L - An unprivileged attacker can drive both sides of the race (epoll_wait as writer and concurrent fd events triggering ep_poll_callback as reader), forcing lock contention into the slowpath; Amazon observed this ordering failure in production on ARM, so success is not dependent on victim-controlled conditions.\nPR:L - epoll_create/epoll_ctl/epoll_wait and ordinary process activity that take rwlocks are available to unprivileged local users with no capabilities or user-namespace privilege escalation required.\nUI:N - Exploitation requires only attacker-controlled threads and file descriptors; no separate victim action such as mounting a filesystem or opening a crafted file is needed.\nS:U - Impact remains within the host kernel's privilege boundary (incorrect mutual exclusion and resulting memory/state corruption), with no VM-escape or other cross-authority scope change.\nC:H - Missing acquire semantics let a writer observe shared kernel state before the write lock is truly held, so protected structures (e.g. ep->ovflist and any other rwlock-guarded data) can be read incorrectly; as a generic rwlock break this enables broad kernel info disclosure via corrupted/racy structure access.\nI:H - The writer then mutates state based on that stale view (e.g. ep_done_scan writing EP_UNACTIVE_PTR over an overflow chain it missed), and broken write-lock exclusivity on widely used rwlocks such as tasklist_lock can corrupt kernel pointer-rich structures, enabling integrity loss and control-flow primitives.\nA:H - Data races from broken qrwlock acquire on structures protected by rwlock_t (epoll lists, tasklist, and others on ARM64/Android) can yield list corruption, use-after-free, and kernel oops/panic under attacker-triggered contention."
|
||
}
|
||
]
|
||
}
|
||
],
|
||
"affected": [
|
||
{
|
||
"product": "Linux",
|
||
"vendor": "Linux",
|
||
"defaultStatus": "unaffected",
|
||
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
|
||
"programFiles": [
|
||
"kernel/locking/qrwlock.c"
|
||
],
|
||
"versions": [
|
||
{
|
||
"version": "b519b56e378ee82caf9b079b04f5db87dedc3251",
|
||
"lessThan": "5902f9453a313be8fe78cbd7e7ca9dba9319fc6e",
|
||
"status": "affected",
|
||
"versionType": "git"
|
||
},
|
||
{
|
||
"version": "b519b56e378ee82caf9b079b04f5db87dedc3251",
|
||
"lessThan": "82808cc026811fbc3ecf0c0b267a12a339eead56",
|
||
"status": "affected",
|
||
"versionType": "git"
|
||
},
|
||
{
|
||
"version": "b519b56e378ee82caf9b079b04f5db87dedc3251",
|
||
"lessThan": "82fa9ced35d88581cffa4a1c856fc41fca96d80a",
|
||
"status": "affected",
|
||
"versionType": "git"
|
||
},
|
||
{
|
||
"version": "b519b56e378ee82caf9b079b04f5db87dedc3251",
|
||
"lessThan": "d558fcdb17139728347bccc60a16af3e639649d2",
|
||
"status": "affected",
|
||
"versionType": "git"
|
||
},
|
||
{
|
||
"version": "b519b56e378ee82caf9b079b04f5db87dedc3251",
|
||
"lessThan": "84a24bf8c52e66b7ac89ada5e3cfbe72d65c1896",
|
||
"status": "affected",
|
||
"versionType": "git"
|
||
}
|
||
]
|
||
},
|
||
{
|
||
"product": "Linux",
|
||
"vendor": "Linux",
|
||
"defaultStatus": "affected",
|
||
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
|
||
"programFiles": [
|
||
"kernel/locking/qrwlock.c"
|
||
],
|
||
"versions": [
|
||
{
|
||
"version": "4.15",
|
||
"status": "affected"
|
||
},
|
||
{
|
||
"version": "0",
|
||
"lessThan": "4.15",
|
||
"status": "unaffected",
|
||
"versionType": "semver"
|
||
},
|
||
{
|
||
"version": "4.19.189",
|
||
"lessThanOrEqual": "4.19.*",
|
||
"status": "unaffected",
|
||
"versionType": "semver"
|
||
},
|
||
{
|
||
"version": "5.4.115",
|
||
"lessThanOrEqual": "5.4.*",
|
||
"status": "unaffected",
|
||
"versionType": "semver"
|
||
},
|
||
{
|
||
"version": "5.10.33",
|
||
"lessThanOrEqual": "5.10.*",
|
||
"status": "unaffected",
|
||
"versionType": "semver"
|
||
},
|
||
{
|
||
"version": "5.11.17",
|
||
"lessThanOrEqual": "5.11.*",
|
||
"status": "unaffected",
|
||
"versionType": "semver"
|
||
},
|
||
{
|
||
"version": "5.12",
|
||
"lessThanOrEqual": "*",
|
||
"status": "unaffected",
|
||
"versionType": "original_commit_for_fix"
|
||
}
|
||
]
|
||
}
|
||
],
|
||
"cpeApplicability": [
|
||
{
|
||
"nodes": [
|
||
{
|
||
"operator": "OR",
|
||
"negate": false,
|
||
"cpeMatch": [
|
||
{
|
||
"vulnerable": true,
|
||
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
|
||
"versionStartIncluding": "4.15",
|
||
"versionEndExcluding": "4.19.189"
|
||
},
|
||
{
|
||
"vulnerable": true,
|
||
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
|
||
"versionStartIncluding": "4.15",
|
||
"versionEndExcluding": "5.4.115"
|
||
},
|
||
{
|
||
"vulnerable": true,
|
||
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
|
||
"versionStartIncluding": "4.15",
|
||
"versionEndExcluding": "5.10.33"
|
||
},
|
||
{
|
||
"vulnerable": true,
|
||
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
|
||
"versionStartIncluding": "4.15",
|
||
"versionEndExcluding": "5.11.17"
|
||
},
|
||
{
|
||
"vulnerable": true,
|
||
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
|
||
"versionStartIncluding": "4.15",
|
||
"versionEndExcluding": "5.12"
|
||
}
|
||
]
|
||
}
|
||
]
|
||
}
|
||
],
|
||
"references": [
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/5902f9453a313be8fe78cbd7e7ca9dba9319fc6e"
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/82808cc026811fbc3ecf0c0b267a12a339eead56"
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/82fa9ced35d88581cffa4a1c856fc41fca96d80a"
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/d558fcdb17139728347bccc60a16af3e639649d2"
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/84a24bf8c52e66b7ac89ada5e3cfbe72d65c1896"
|
||
}
|
||
],
|
||
"title": "locking/qrwlock: Fix ordering in queued_write_lock_slowpath()",
|
||
"x_generator": {
|
||
"engine": "bippy-1.2.0"
|
||
}
|
||
},
|
||
"adp": [
|
||
{
|
||
"metrics": [
|
||
{
|
||
"other": {
|
||
"type": "ssvc",
|
||
"content": {
|
||
"id": "CVE-2021-46921",
|
||
"role": "CISA Coordinator",
|
||
"options": [
|
||
{
|
||
"Exploitation": "none"
|
||
},
|
||
{
|
||
"Automatable": "no"
|
||
},
|
||
{
|
||
"Technical Impact": "partial"
|
||
}
|
||
],
|
||
"version": "2.0.3",
|
||
"timestamp": "2024-02-27T16:11:46.310286Z"
|
||
}
|
||
}
|
||
}
|
||
],
|
||
"title": "CISA ADP Vulnrichment",
|
||
"providerMetadata": {
|
||
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
|
||
"shortName": "CISA-ADP",
|
||
"dateUpdated": "2024-07-05T17:22:01.427Z"
|
||
}
|
||
},
|
||
{
|
||
"providerMetadata": {
|
||
"orgId": "af854a3a-2127-422b-91ae-364da2661108",
|
||
"shortName": "CVE",
|
||
"dateUpdated": "2024-08-04T05:17:42.848Z"
|
||
},
|
||
"title": "CVE Program Container",
|
||
"references": [
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/5902f9453a313be8fe78cbd7e7ca9dba9319fc6e",
|
||
"tags": [
|
||
"x_transferred"
|
||
]
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/82808cc026811fbc3ecf0c0b267a12a339eead56",
|
||
"tags": [
|
||
"x_transferred"
|
||
]
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/82fa9ced35d88581cffa4a1c856fc41fca96d80a",
|
||
"tags": [
|
||
"x_transferred"
|
||
]
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/d558fcdb17139728347bccc60a16af3e639649d2",
|
||
"tags": [
|
||
"x_transferred"
|
||
]
|
||
},
|
||
{
|
||
"url": "https://git.kernel.org/stable/c/84a24bf8c52e66b7ac89ada5e3cfbe72d65c1896",
|
||
"tags": [
|
||
"x_transferred"
|
||
]
|
||
}
|
||
]
|
||
}
|
||
]
|
||
}
|
||
} |