Linux Kernel: smc91x IRQ Context Bug (PREEMPT_RT)
CVE-2025-71132 Published on January 14, 2026
smc91x: fix broken irq-context in PREEMPT_RT
In the Linux kernel, the following vulnerability has been resolved:
smc91x: fix broken irq-context in PREEMPT_RT
When smc91x.c is built with PREEMPT_RT, the following splat occurs
in FVP_RevC:
[ 13.055000] smc91x LNRO0003:00 eth0: link up, 10Mbps, half-duplex, lpa 0x0000
[ 13.062137] BUG: workqueue leaked atomic, lock or RCU: kworker/2:1[106]
[ 13.062137] preempt=0x00000000 lock=0->0 RCU=0->1 workfn=mld_ifc_work
[ 13.062266] C
** replaying previous printk message **
[ 13.062266] CPU: 2 UID: 0 PID: 106 Comm: kworker/2:1 Not tainted 6.18.0-dirty #179 PREEMPT_{RT,(full)}
[ 13.062353] Hardware name: , BIOS
[ 13.062382] Workqueue: mld mld_ifc_work
[ 13.062469] Call trace:
[ 13.062494] show_stack+0x24/0x40 (C)
[ 13.062602] __dump_stack+0x28/0x48
[ 13.062710] dump_stack_lvl+0x7c/0xb0
[ 13.062818] dump_stack+0x18/0x34
[ 13.062926] process_scheduled_works+0x294/0x450
[ 13.063043] worker_thread+0x260/0x3d8
[ 13.063124] kthread+0x1c4/0x228
[ 13.063235] ret_from_fork+0x10/0x20
This happens because smc_special_trylock() disables IRQs even on PREEMPT_RT,
but smc_special_unlock() does not restore IRQs on PREEMPT_RT.
The reason is that smc_special_unlock() calls spin_unlock_irqrestore(),
and rcu_read_unlock_bh() in __dev_queue_xmit() cannot invoke
rcu_read_unlock() through __local_bh_enable_ip() when current->softirq_disable_cnt becomes zero.
To address this issue, replace smc_special_trylock() with spin_trylock_irqsave().
Products Associated with CVE-2025-71132
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Affected Versions
Linux:- Version 342a93247e0837101f27bbcca26f402902df98dc and below 1c4cb705e733250d13243f6a69b8b5a92e39b9f6 is affected.
- Version 342a93247e0837101f27bbcca26f402902df98dc and below 9d222141b00156509d67d80c771fbefa92c43ace is affected.
- Version 342a93247e0837101f27bbcca26f402902df98dc and below ef277ae121b3249c99994652210a326b52d527b0 is affected.
- Version 342a93247e0837101f27bbcca26f402902df98dc and below 36561b86cb2501647662cfaf91286dd6973804a6 is affected.
- Version 342a93247e0837101f27bbcca26f402902df98dc and below b6018d5c1a8f09d5efe4d6961d7ee45fdf3a7ce3 is affected.
- Version 342a93247e0837101f27bbcca26f402902df98dc and below 6402078bd9d1ed46e79465e1faaa42e3458f8a33 is affected.
- Version 5.15 is affected.
- Before 5.15 is unaffected.
- Version 5.15.198, <= 5.15.* is unaffected.
- Version 6.1.160, <= 6.1.* is unaffected.
- Version 6.6.120, <= 6.6.* is unaffected.
- Version 6.12.64, <= 6.12.* is unaffected.
- Version 6.18.4, <= 6.18.* is unaffected.
- Version 6.19, <= * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.