GHSA-RFHV-4P96-VM65
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-10-21 15:41In the Linux kernel, the following vulnerability has been resolved:
tracing: Undo the registration when enabling the histogram trigger fails
Commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers list") described how a trigger that is registered but not on file->triggers ends up freed while still on the global named_triggers list, and moved the registration down so that hist_trigger_enable() follows it immediately. One path still gets there. hist_trigger_enable() adds the trigger and takes it straight back out when the event cannot be enabled:
list_add_tail_rcu(&data->list, &file->triggers);
update_cond_flag(file);
if (trace_event_trigger_enable_disable(file, 1) < 0) {
list_del_rcu(&data->list);
update_cond_flag(file);
ret--;
}
so the list walk in hist_unregister_trigger() matches nothing, test stays NULL, and the ->free() that would call del_named_trigger() is skipped. out_unreg falls through to out_free, which frees the trigger anyway:
BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0 Read of size 8 at addr ffff8880091d3160 by task init/1 find_named_trigger+0xac/0xc0 hist_register_trigger+0xc1/0xa00 event_hist_trigger_parse+0x3146/0x6af0 event_trigger_write+0xce/0x160 Freed by task 69: kfree+0x154/0x420 trigger_kthread_fn+0xfd/0x160
Leave the trigger where hist_unregister_trigger() can find it and let that undo the registration, which is the only code that knows all of what cmd_ops->init() took: the named list entry, the hist_pad reference, the reference on the trigger a named histogram is shared with, and the copied cmd_ops. It also pairs the failed trace_event_trigger_enable_disable(), whose sm_ref and buffered event reference are otherwise left behind.
Since ->free() releases trigger_data and, for a trigger that does not share its histogram, hist_data with it, out_unreg can no longer fall through to out_free. For a trigger that does share, hist_register_trigger() has already destroyed the caller's hist_data, so the fall-through was reading freed memory there as well.
Move the enable_timestamps check in hist_unregister_trigger() above the ->free() call for the same reason: hist_data does not outlive it once the trigger being removed is the one that owns it.
{
"affected": [],
"aliases": [
"CVE-2026-97918"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:18Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Undo the registration when enabling the histogram trigger fails\n\nCommit 6f86bdeab633 (\"tracing: Fix bad hist from corrupting named_triggers\nlist\") described how a trigger that is registered but not on file-\u003etriggers\nends up freed while still on the global named_triggers list, and moved the\nregistration down so that hist_trigger_enable() follows it immediately. One\npath still gets there. hist_trigger_enable() adds the trigger and takes it\nstraight back out when the event cannot be enabled:\n\n\tlist_add_tail_rcu(\u0026data-\u003elist, \u0026file-\u003etriggers);\n\n\tupdate_cond_flag(file);\n\n\tif (trace_event_trigger_enable_disable(file, 1) \u003c 0) {\n\t\tlist_del_rcu(\u0026data-\u003elist);\n\t\tupdate_cond_flag(file);\n\t\tret--;\n\t}\n\nso the list walk in hist_unregister_trigger() matches nothing, test stays\nNULL, and the -\u003efree() that would call del_named_trigger() is skipped.\nout_unreg falls through to out_free, which frees the trigger anyway:\n\n BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0\n Read of size 8 at addr ffff8880091d3160 by task init/1\n find_named_trigger+0xac/0xc0\n hist_register_trigger+0xc1/0xa00\n event_hist_trigger_parse+0x3146/0x6af0\n event_trigger_write+0xce/0x160\n Freed by task 69:\n kfree+0x154/0x420\n trigger_kthread_fn+0xfd/0x160\n\nLeave the trigger where hist_unregister_trigger() can find it and let that\nundo the registration, which is the only code that knows all of what\ncmd_ops-\u003einit() took: the named list entry, the hist_pad reference, the\nreference on the trigger a named histogram is shared with, and the copied\ncmd_ops. It also pairs the failed trace_event_trigger_enable_disable(),\nwhose sm_ref and buffered event reference are otherwise left behind.\n\nSince -\u003efree() releases trigger_data and, for a trigger that does not share\nits histogram, hist_data with it, out_unreg can no longer fall through to\nout_free. For a trigger that does share, hist_register_trigger() has\nalready destroyed the caller\u0027s hist_data, so the fall-through was reading\nfreed memory there as well.\n\nMove the enable_timestamps check in hist_unregister_trigger() above the\n-\u003efree() call for the same reason: hist_data does not outlive it once the\ntrigger being removed is the one that owns it.",
"id": "GHSA-rfhv-4p96-vm65",
"modified": "2026-10-21T15:41:36Z",
"published": "2026-09-25T12:31:28Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97918"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/51b07104d563d4be2be34158d3b9d922ca417642"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/880712b6f48103ba3a04b154ff076d45fe86dcec"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/92383cef66791a0c63a2f27755cadbdb2fbf270b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bfa6bc11aef93a3d9db0ac9564b734849a9d959b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c7ee2d5733574d4694f7c0035e4381f54c1fca27"
}
],
"schema_version": "1.4.0",
"severity": []
}
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