perf: Fix use-after-free when perf mmap() revival races with the last munmap()
In the Linux kernel, the following vulnerability has been resolved: perf: Fix use-after-free when perf mmap() revival races with the last munmap() perf_mmap_close() drops rb->mmap_count *without* holding event->mmap_mutex (the refcount_dec_and_test() right before the refcount_dec_and_mutex_lock() of event->mmap_count). A concurrent perf_mmap_rb() can slot its entire "revival" path into that window (perf_mmap holds event->mmap_mutex for its whole duration, including rb_alloc): munmap side (perf_mmap_close) mmap side (perf_mmap_rb) ----------------------------------- -------------------------------- rb->mmap_count 1 -> 0 (no lock) (holds event->mmap_mutex) inc_not_zero(rb->mmap_count) fails ring_buffer_attach(event, NULL) rb_alloc() + attach new rb refcount_set(&event->mmap_count, 1) lock; event->mmap_count 1 -> 0 ring_buffer_attach(event, NULL) ring_buffer_put() -> frees the *new* rb The revival's refcount_set(&event->mmap_count, 1) is an invisible 1 -> 1 write: the close frees the just-revived buffer although the other process still has it mapped -- a page-level use-after-free allowing local privilege escalation to root by any unprivileged user (default kernel.perf_event_paranoid=2). Swap the order of the two counter updates: event->mmap_count is dropped first via refcount_dec_and_mutex_lock(), so its 1 -> 0 transition and the ring_buffer_attach() stay serialized with perf_mmap(). rb->mmap_count == 0 then implies every event using the buffer is detached already, so the result
CVE-2026-89791
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-2026-89791
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": "59741451b49ce9964a9758c19d6f7df2a1255c75",
"lessThan": "929cb3b9dc818dd9fa89d510d4ff2b255e42badd",
"versionType": "git"
},
{
"status": "affected",
"version": "59741451b49ce9964a9758c19d6f7df2a1255c75",
"lessThan": "0c739f54f1c77f3a4643160cd2e031b6c2f2aab6",
"versionType": "git"
},
{
"status": "affected",
"version": "59741451b49ce9964a9758c19d6f7df2a1255c75",
"lessThan": "58a8108bc73de0740d5b88150465d6690ea5f85f",
"versionType": "git"
}
],
"programFiles": [
"kernel/events/core.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.18"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.18",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.18.52",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.5",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/events/core.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89791
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #36261 · Revision 1
- Added to Heist Feed
- Publisher date