GHSA-7R96-J35V-9X4X
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 15:31In the Linux kernel, the following vulnerability has been resolved:
nstree: check listing permission before taking a namespace reference
legitimize_ns() takes a reference on the candidate namespace before may_list_ns() has decided whether the caller may see it. The __free(ns_put) cleanup on the denied path can drop the last reference to a mount namespace while we still hold the rcu read lock, and put_mnt_ns() may sleep there. This is the same problem commit 2ec2aff3c8e2 ("ns: make sure reference are dropped outside of rcu lock") fixed for the put_user() path. Neither ns_requested() nor may_list_ns() needs a reference, both only look at the namespace type and at the caller's own namespaces, so do the checks first and take the reference last.
Splat:
Voluntary context switch within RCU read-side critical section! WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0x238/0x2a0, CPU#5: a/3442 CPU: 5 UID: 1000 PID: 3442 Comm: a Not tainted 7.0.0-30-generic #30-Ubuntu PREEMPT(lazy) RIP: 0010:rcu_note_context_switch+0x238/0x2a0 Call Trace: __schedule+0xcf/0x650 schedule+0x27/0x90 schedule_preempt_disabled+0x15/0x30 __mutex_lock.constprop.0+0x550/0xaf0 __mutex_lock_slowpath+0x13/0x20 mutex_lock+0x3b/0x50 exp_funnel_lock+0xb2/0x260 synchronize_rcu_expedited+0xe7/0x220 namespace_unlock+0x26a/0x320 put_mnt_ns+0xd3/0x120 mntns_put+0xe/0x20 do_listns+0x13e/0x560 __do_sys_listns+0x126/0x2d0 __x64_sys_listns+0x20/0x30 x64_sys_call+0x2366/0x2390 do_syscall_64+0x105/0x5a0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
{
"affected": [],
"aliases": [
"CVE-2026-97971"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:24Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnstree: check listing permission before taking a namespace reference\n\nlegitimize_ns() takes a reference on the candidate namespace before\nmay_list_ns() has decided whether the caller may see it. The\n__free(ns_put) cleanup on the denied path can drop the last reference to a\nmount namespace while we still hold the rcu read lock, and put_mnt_ns()\nmay sleep there. This is the same problem commit 2ec2aff3c8e2 (\"ns: make\nsure reference are dropped outside of rcu lock\") fixed for the put_user()\npath. Neither ns_requested() nor may_list_ns() needs a reference, both\nonly look at the namespace type and at the caller\u0027s own namespaces, so do\nthe checks first and take the reference last.\n\nSplat:\n\n Voluntary context switch within RCU read-side critical section!\n WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0x238/0x2a0, CPU#5: a/3442\n CPU: 5 UID: 1000 PID: 3442 Comm: a Not tainted 7.0.0-30-generic #30-Ubuntu PREEMPT(lazy)\n RIP: 0010:rcu_note_context_switch+0x238/0x2a0\n Call Trace:\n \u003cTASK\u003e\n __schedule+0xcf/0x650\n schedule+0x27/0x90\n schedule_preempt_disabled+0x15/0x30\n __mutex_lock.constprop.0+0x550/0xaf0\n __mutex_lock_slowpath+0x13/0x20\n mutex_lock+0x3b/0x50\n exp_funnel_lock+0xb2/0x260\n synchronize_rcu_expedited+0xe7/0x220\n namespace_unlock+0x26a/0x320\n put_mnt_ns+0xd3/0x120\n mntns_put+0xe/0x20\n do_listns+0x13e/0x560\n __do_sys_listns+0x126/0x2d0\n __x64_sys_listns+0x20/0x30\n x64_sys_call+0x2366/0x2390\n do_syscall_64+0x105/0x5a0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n \u003c/TASK\u003e",
"id": "GHSA-7r96-j35v-9x4x",
"modified": "2026-09-25T15:31:44Z",
"published": "2026-09-25T12:31:30Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97971"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/56ea4e86832d8abe8930394473566c194d189f85"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9e673bf5d88aa898e52cef5c87058c3fa845bc71"
}
],
"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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