Bug 2394635 (CVE-2025-39745) - CVE-2025-39745 kernel: rcutorture: Fix rcutorture_one_extend_check() splat in RT kernels
Summary: CVE-2025-39745 kernel: rcutorture: Fix rcutorture_one_extend_check() splat in...
Keywords:
Status: NEW
Alias: CVE-2025-39745
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
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Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2025-09-11 17:03 UTC by OSIDB Bzimport
Modified: 2025-09-22 13:26 UTC (History)
0 users

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Description OSIDB Bzimport 2025-09-11 17:03:49 UTC 
In the Linux kernel, the following vulnerability has been resolved:

rcutorture: Fix rcutorture_one_extend_check() splat in RT kernels

For built with CONFIG_PREEMPT_RT=y kernels, running rcutorture
tests resulted in the following splat:

[   68.797425] rcutorture_one_extend_check during change: Current 0x1  To add 0x1  To remove 0x0  preempt_count() 0x0
[   68.797533] WARNING: CPU: 2 PID: 512 at kernel/rcu/rcutorture.c:1993 rcutorture_one_extend_check+0x419/0x560 [rcutorture]
[   68.797601] Call Trace:
[   68.797602]  <TASK>
[   68.797619]  ? lockdep_softirqs_off+0xa5/0x160
[   68.797631]  rcutorture_one_extend+0x18e/0xcc0 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c]
[   68.797646]  ? local_clock+0x19/0x40
[   68.797659]  rcu_torture_one_read+0xf0/0x280 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c]
[   68.797678]  ? __pfx_rcu_torture_one_read+0x10/0x10 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c]
[   68.797804]  ? __pfx_rcu_torture_timer+0x10/0x10 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c]
[   68.797815] rcu-torture: rcu_torture_reader task started
[   68.797824] rcu-torture: Creating rcu_torture_reader task
[   68.797824]  rcu_torture_reader+0x238/0x580 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c]
[   68.797836]  ? kvm_sched_clock_read+0x15/0x30

Disable BH does not change the SOFTIRQ corresponding bits in
preempt_count() for RT kernels, this commit therefore use
softirq_count() to check the if BH is disabled.
Comment 1 Mauro Matteo Cascella 2025-09-22 13:23:41 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025091140-CVE-2025-39745-ac0b@gregkh/T
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