GHSA-PF29-FJPW-V4G4
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32In the Linux kernel, the following vulnerability has been resolved:
tracing/user_events: Clear copied tracing state before fork duplication
dup_task_struct() copies user_event_mm from the parent into the child, without grabbing a reference to it. user_event_mm_dup() should replace it, but it leaves that copied pointer unmodified if user_event_mm_alloc() fails.
When the child exits, user_event_mm_remove() decrements a reference the child never owned, which ultimately frees user_event_mm, while the parent still as a stale pointer to it. This creates a UAF, which KASAN reports as:
BUG: KASAN: slab-use-after-free in
current_user_event_mm+0x51/0x1d0 Write of size 4 at addr
ffff888005010d30 by task init/44
Call Trace:
<TASK>
kasan_report+0xce/0x100
kasan_check_range+0x10f/0x1e0
current_user_event_mm+0x51/0x1d0
user_events_ioctl+0x82e/0x15c0
__x64_sys_ioctl+0x139/0x1c0
do_syscall_64+0xce/0x450
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Allocated by task 44:
__kasan_kmalloc+0x8f/0xa0
__kmalloc_cache_noprof+0x180/0x3a0
user_event_mm_alloc+0x3c/0x1f0
current_user_event_mm+0x88/0x1d0
Freed by task 42:
__kasan_slab_free+0x43/0x70
kfree+0x13a/0x390
process_one_work+0x696/0xf90
worker_thread+0x420/0xba0
The fix simply clears the copied pointer before any possible failure. In case of failure, the child then has nothing to free.
{
"affected": [],
"aliases": [
"CVE-2026-89750"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:20:05Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing/user_events: Clear copied tracing state before fork duplication\n\ndup_task_struct() copies user_event_mm from the parent into the child,\nwithout grabbing a reference to it. user_event_mm_dup() should\nreplace it, but it leaves that copied pointer unmodified if\nuser_event_mm_alloc() fails.\n\nWhen the child exits, user_event_mm_remove() decrements a reference\nthe child never owned, which ultimately frees user_event_mm, while\nthe parent still as a stale pointer to it. This creates a UAF, which\nKASAN reports as:\n\n BUG: KASAN: slab-use-after-free in\n current_user_event_mm+0x51/0x1d0 Write of size 4 at addr\n ffff888005010d30 by task init/44\n\n Call Trace:\n \u003cTASK\u003e\n kasan_report+0xce/0x100\n kasan_check_range+0x10f/0x1e0\n current_user_event_mm+0x51/0x1d0\n user_events_ioctl+0x82e/0x15c0\n __x64_sys_ioctl+0x139/0x1c0\n do_syscall_64+0xce/0x450\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n Allocated by task 44:\n __kasan_kmalloc+0x8f/0xa0\n __kmalloc_cache_noprof+0x180/0x3a0\n user_event_mm_alloc+0x3c/0x1f0\n current_user_event_mm+0x88/0x1d0\n\n Freed by task 42:\n __kasan_slab_free+0x43/0x70\n kfree+0x13a/0x390\n process_one_work+0x696/0xf90\n worker_thread+0x420/0xba0\n\nThe fix simply clears the copied pointer before any possible failure.\nIn case of failure, the child then has nothing to free.",
"id": "GHSA-pf29-fjpw-v4g4",
"modified": "2026-09-14T15:32:36Z",
"published": "2026-09-11T21:31:39Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89750"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/25a0758cf6bdbfddac2be71124c9bd0692f4b0b1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/33ce55b368b64d65941867add00e7f288cbb8234"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/390f6bd8583d177029d9df4bea6667509e55a765"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/63b39e49a4c9d68e010e96b26fc7374f0864f2b1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b799f67119aff179719a0b1e12441ebbdaaf62f9"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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