CVE-2025-71132

Description

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().

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel smc91x driver (PREEMPT_RT enabled)

FVP_RevC platform with smc91x ethernet interface

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

// CVE-2025-71132 PoC - 触发smc91x IRQ上下文泄漏
// 条件：Linux Kernel with PREEMPT_RT enabled, smc91x driver loaded

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>

/* Trigger conditions:
 * 1. Kernel compiled with CONFIG_PREEMPT_RT
 * 2. smc91x network driver loaded and active
 * 3. Network interface operational (link up)
 * 4. Trigger network traffic to invoke smc91x transmit path
 * 
 * Expected result: BUG warning about workqueue leaked atomic context
 */

static int __init cve_2025_71132_init(void)
{
    printk(KERN_INFO "CVE-2025-71132 PoC: smc91x RT lock issue\n");
    /* The bug is triggered through normal network operations
     * when smc91x driver processes TX packets with PREEMPT_RT
     */
    return 0;
}

static void __exit cve_2025_71132_exit(void)
{
    printk(KERN_INFO "CVE-2025-71132 PoC unloaded\n");
}

module_init(cve_2025_71132_init);
module_exit(cve_2025_71132_exit);
MODULE_LICENSE("GPL");

/* Mitigation: Apply kernel patch replacing smc_special_trylock()
 * with spin_trylock_irqsave() in smc91x.c
 * Commit: 1c4cb705e733250d13243f6a69b8b5a92e39b9f6
 */

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2025-71132
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2025-71132
[3] CVE Details https://www.cvedetails.com/cve/CVE-2025-71132/
[4] VulDB https://vuldb.com/cve/CVE-2025-71132
[5] https://git.kernel.org/stable/c/1c4cb705e733250d13243f6a69b8b5a92e39b9f6
[6] https://git.kernel.org/stable/c/36561b86cb2501647662cfaf91286dd6973804a6
[7] https://git.kernel.org/stable/c/6402078bd9d1ed46e79465e1faaa42e3458f8a33
[8] https://git.kernel.org/stable/c/9d222141b00156509d67d80c771fbefa92c43ace
[9] https://git.kernel.org/stable/c/b6018d5c1a8f09d5efe4d6961d7ee45fdf3a7ce3
[10] https://git.kernel.org/stable/c/ef277ae121b3249c99994652210a326b52d527b0

Raw JSON Data

JSON

{"cve": {"id": "CVE-2025-71132", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-01-14T15:16:02.947", "lastModified": "2026-03-25T19:56:03.873", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmc91x: fix broken irq-context in PREEMPT_RT\n\nWhen smc91x.c is built with PREEMPT_RT, the following splat occurs\nin FVP_RevC:\n\n[ 13.055000] smc91x LNRO0003:00 eth0: link up, 10Mbps, half-duplex, lpa 0x0000\n[ 13.062137] BUG: workqueue leaked atomic, lock or RCU: kworker/2:1[106]\n[ 13.062137] preempt=0x00000000 lock=0->0 RCU=0->1 workfn=mld_ifc_work\n[ 13.062266] C\n** replaying previous printk message **\n[ 13.062266] CPU: 2 UID: 0 PID: 106 Comm: kworker/2:1 Not tainted 6.18.0-dirty #179 PREEMPT_{RT,(full)}\n[ 13.062353] Hardware name: , BIOS\n[ 13.062382] Workqueue: mld mld_ifc_work\n[ 13.062469] Call trace:\n[ 13.062494] show_stack+0x24/0x40 (C)\n[ 13.062602] __dump_stack+0x28/0x48\n[ 13.062710] dump_stack_lvl+0x7c/0xb0\n[ 13.062818] dump_stack+0x18/0x34\n[ 13.062926] process_scheduled_works+0x294/0x450\n[ 13.063043] worker_thread+0x260/0x3d8\n[ 13.063124] kthread+0x1c4/0x228\n[ 13.063235] ret_from_fork+0x10/0x20\n\nThis happens because smc_special_trylock() disables IRQs even on PREEMPT_RT,\nbut smc_special_unlock() does not restore IRQs on PREEMPT_RT.\nThe reason is that smc_special_unlock() calls spin_unlock_irqrestore(),\nand rcu_read_unlock_bh() in __dev_queue_xmit() cannot invoke\nrcu_read_unlock() through __local_bh_enable_ip() when current->softirq_disable_cnt becomes zero.\n\nTo address this issue, replace smc_special_trylock() with spin_trylock_irqsave()."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nsmc91x: corregir el contexto de IRQ roto en PREEMPT_RT\n\nCuando smc91x.c se compila con PREEMPT_RT, ocurre el siguiente 'splat' en FVP_RevC:\n\n[ 13.055000] smc91x LNRO0003:00 eth0: link up, 10Mbps, half-duplex, lpa 0x0000\n[ 13.062137] BUG: workqueue leaked atomic, lock or RCU: kworker/2:1[106]\n[ 13.062137] preempt=0x00000000 lock=0->0 RCU=0->1 workfn=mld_ifc_work\n[ 13.062266] C\n replaying previous printk message \n[ 13.062266] CPU: 2 UID: 0 PID: 106 Comm: kworker/2:1 Not tainted 6.18.0-dirty #179 PREEMPT_{RT,(full)}\n[ 13.062353] Hardware name: , BIOS\n[ 13.062382] Workqueue: mld mld_ifc_work\n[ 13.062469] Call trace:\n[ 13.062494] show_stack+0x24/0x40 (C)\n[ 13.062602] __dump_stack+0x28/0x48\n[ 13.062710] dump_stack_lvl+0x7c/0xb0\n[ 13.062818] dump_stack+0x18/0x34\n[ 13.062926] process_scheduled_works+0x294/0x450\n[ 13.063043] worker_thread+0x260/0x3d8\n[ 13.063124] kthread+0x1c4/0x228\n[ 13.063235] ret_from_fork+0x10/0x20\n\nEsto ocurre porque smc_special_trylock() deshabilita las IRQ incluso en PREEMPT_RT, pero smc_special_unlock() no restaura las IRQ en PREEMPT_RT.\nLa razón es que smc_special_unlock() llama a spin_unlock_irqrestore(), y rcu_read_unlock_bh() en __dev_queue_xmit() no puede invocar a rcu_read_unlock() a través de __local_bh_enable_ip() cuando current->softirq_disable_cnt se vuelve cero.\n\nPara abordar este problema, reemplace smc_special_trylock() con spin_trylock_irqsave()."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.1", "versionEndExcluding": "5.15.198", "matchCriteriaId": "5BEC28A5-0DC2-4D3D-A401-40D4AEA6C42A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.160", "matchCriteriaId": "C10CC03E-16A9-428A-B449-40D3763E15F6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.120", "matchCriteriaId": "43C3A206-5EEE-417B-AA0F-EF8972E7A9F0"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.64", "matchCriteriaId": "32BF4A52-377C-44ED-B5E6-7EA5D896E98B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionE ... (truncated)