GHSA-M56H-PFXH-QXQ7
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: Fix use-after-free with same-name named triggers
When two hist triggers on different events are registered with the same name=, the second one reuses the first as named_data. Both are added to tr->hist_vars by save_hist_vars() during event_hist_trigger_parse(), because save_hist_vars() is called before event_trigger_register() while the named reuse is only detected later, in hist_register_trigger().
In the named-data branch hist_register_trigger() then frees the second histogram's hist_data via destroy_hist_data(), but never removes its tr->hist_vars list entry, leaving a dangling pointer and leaking the trace_array reference it holds.
A later hist trigger that references a variable makes find_var_file() walk tr->hist_vars and dereference the freed hist_data. The bug is reproducible from userspace by writing three hist triggers to tracefs:
cd /sys/kernel/tracing echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_switch/trigger echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_process_fork/trigger echo 'hist:keys=common_pid:vals=$x' > events/sched/sched_process_exit/trigger
The third write panics the kernel:
BUG: KASAN: slab-use-after-free in find_var_file.part.0+0x272/0x290 Read of size 8 at addr ffff888001f8a0e0 by task sh/1 CPU: 1 UID: 0 PID: 1 Comm: sh Tainted: G D N Call Trace: find_var_file.part.0 find_event_var parse_atom parse_expr __create_val_field event_hist_trigger_parse trigger_process_regex event_trigger_write vfs_write ksys_write do_syscall_64 entry_SYSCALL_64_after_hwframe Allocated by task 1: event_hist_trigger_parse Freed by task 1: hist_register_trigger+0x618/0xa30 event_hist_trigger_parse The buggy address belongs to freed 2048-byte region Oops: general protection fault ... RIP: find_var_file.part.0 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
Fix by removing the hist_data from tr->hist_vars and releasing the trace_array reference in the named-data branch of hist_register_trigger() before freeing the hist_data.
{
"affected": [],
"aliases": [
"CVE-2026-89746"
],
"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: Fix use-after-free with same-name named triggers\n\nWhen two hist triggers on different events are registered with the same\nname=, the second one reuses the first as named_data. Both are added to\ntr-\u003ehist_vars by save_hist_vars() during event_hist_trigger_parse(),\nbecause save_hist_vars() is called before event_trigger_register() while\nthe named reuse is only detected later, in hist_register_trigger().\n\nIn the named-data branch hist_register_trigger() then frees the second\nhistogram\u0027s hist_data via destroy_hist_data(), but never removes its\ntr-\u003ehist_vars list entry, leaving a dangling pointer and leaking the\ntrace_array reference it holds.\n\nA later hist trigger that references a variable makes find_var_file()\nwalk tr-\u003ehist_vars and dereference the freed hist_data. The bug is\nreproducible from userspace by writing three hist triggers to tracefs:\n\n cd /sys/kernel/tracing\n echo \u0027hist:keys=common_pid:x=common_pid:name=mh\u0027 \u003e events/sched/sched_switch/trigger\n echo \u0027hist:keys=common_pid:x=common_pid:name=mh\u0027 \u003e events/sched/sched_process_fork/trigger\n echo \u0027hist:keys=common_pid:vals=$x\u0027 \u003e events/sched/sched_process_exit/trigger\n\nThe third write panics the kernel:\n\n BUG: KASAN: slab-use-after-free in find_var_file.part.0+0x272/0x290\n Read of size 8 at addr ffff888001f8a0e0 by task sh/1\n CPU: 1 UID: 0 PID: 1 Comm: sh Tainted: G D N\n Call Trace:\n find_var_file.part.0\n find_event_var\n parse_atom\n parse_expr\n __create_val_field\n event_hist_trigger_parse\n trigger_process_regex\n event_trigger_write\n vfs_write\n ksys_write\n do_syscall_64\n entry_SYSCALL_64_after_hwframe\n Allocated by task 1:\n event_hist_trigger_parse\n Freed by task 1:\n hist_register_trigger+0x618/0xa30\n event_hist_trigger_parse\n The buggy address belongs to freed 2048-byte region\n Oops: general protection fault ... RIP: find_var_file.part.0\n Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b\n\nFix by removing the hist_data from tr-\u003ehist_vars and releasing the\ntrace_array reference in the named-data branch of hist_register_trigger()\nbefore freeing the hist_data.",
"id": "GHSA-m56h-pfxh-qxq7",
"modified": "2026-09-14T15:32:36Z",
"published": "2026-09-11T21:31:39Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89746"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3a8534664426c071c2dfb5b4ffa36b18a2abfd79"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/441aa6742dff70297b5f64533a07a6189a026e91"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/477d762be4b0ffaf01429ccd88859e93b0ec28cc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/83d1ae0406d8eade219a81b401e201702dd9dc55"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a7318172aa332a161fb9618286e64454c827f8fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b1a49c22de01faf176d44e5caa765e237353a579"
}
],
"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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