Description
In 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:
<TASK>
__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
</TASK>
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:
<TASK>
__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
</TASK>
Published:
2026-09-25
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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Advisories
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References
History
Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In 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: <TASK> __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 </TASK> | |
| Title | nstree: check listing permission before taking a namespace reference | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:23:11.539Z
Reserved: 2026-09-25T10:18:58.207Z
Link: CVE-2026-97971
Vulnrichment
No data.
NVD
No data.
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.