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CVE-2025-39749— rcu: Protect ->defer_qs_iw_pending from data race

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于对rcu_data结构中的defer_qs_iw_pending字段缺乏保护，可能导致数据竞争。

AI Predicted 5.3 Difficulty: Theoretical EPSS 0.17% · P7

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 20

VendorProduct Version RangeStatus
Linux Linux 0864f057b050bc6dd68106b3185e02db5140012d< 74f58f382a7c8333f8d09701aefaa25913bdbe0e affected
0864f057b050bc6dd68106b3185e02db5140012d< f937759c7432d6151b73e1393b6517661813d506 affected
0864f057b050bc6dd68106b3185e02db5140012d< 0ad84d62217488e679ecc90e8628980dcc003de3 affected
0864f057b050bc6dd68106b3185e02db5140012d< b5de8d80b5d049f051b95d9b1ee50ae4ab656124 affected
0864f057b050bc6dd68106b3185e02db5140012d< b55947b725f190396f475d5d0c59aa855a4d8895 affected
0864f057b050bc6dd68106b3185e02db5140012d< e35e711c78c8a4c43330c0dcb1c4d507a19c20f4 affected
0864f057b050bc6dd68106b3185e02db5140012d< 90de9c94ea72327cfa9c2c9f6113c23a513af60b affected
0864f057b050bc6dd68106b3185e02db5140012d< 55e11f6776798b27cf09a7aa0d718415d4fc9cf5 affected
… +12 more rows
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I. Basic Information for CVE-2025-39749

Vulnerability Information
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Vulnerability Title
rcu: Protect ->defer_qs_iw_pending from data race
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: rcu: Protect ->defer_qs_iw_pending from data race On kernels built with CONFIG_IRQ_WORK=y, when rcu_read_unlock() is invoked within an interrupts-disabled region of code [1], it will invoke rcu_read_unlock_special(), which uses an irq-work handler to force the system to notice when the RCU read-side critical section actually ends. That end won't happen until interrupts are enabled at the soonest. In some kernels, such as those booted with rcutree.use_softirq=y, the irq-work handler is used unconditionally. The per-CPU rcu_data structure's ->defer_qs_iw_pending field is updated by the irq-work handler and is both read and updated by rcu_read_unlock_special(). This resulted in the following KCSAN splat: ------------------------------------------------------------------------ BUG: KCSAN: data-race in rcu_preempt_deferred_qs_handler / rcu_read_unlock_special read to 0xffff96b95f42d8d8 of 1 bytes by task 90 on cpu 8: rcu_read_unlock_special+0x175/0x260 __rcu_read_unlock+0x92/0xa0 rt_spin_unlock+0x9b/0xc0 __local_bh_enable+0x10d/0x170 __local_bh_enable_ip+0xfb/0x150 rcu_do_batch+0x595/0xc40 rcu_cpu_kthread+0x4e9/0x830 smpboot_thread_fn+0x24d/0x3b0 kthread+0x3bd/0x410 ret_from_fork+0x35/0x40 ret_from_fork_asm+0x1a/0x30 write to 0xffff96b95f42d8d8 of 1 bytes by task 88 on cpu 8: rcu_preempt_deferred_qs_handler+0x1e/0x30 irq_work_single+0xaf/0x160 run_irq_workd+0x91/0xc0 smpboot_thread_fn+0x24d/0x3b0 kthread+0x3bd/0x410 ret_from_fork+0x35/0x40 ret_from_fork_asm+0x1a/0x30 no locks held by irq_work/8/88. irq event stamp: 200272 hardirqs last enabled at (200272): [<ffffffffb0f56121>] finish_task_switch+0x131/0x320 hardirqs last disabled at (200271): [<ffffffffb25c7859>] __schedule+0x129/0xd70 softirqs last enabled at (0): [<ffffffffb0ee093f>] copy_process+0x4df/0x1cc0 softirqs last disabled at (0): [<0000000000000000>] 0x0 ------------------------------------------------------------------------ The problem is that irq-work handlers run with interrupts enabled, which means that rcu_preempt_deferred_qs_handler() could be interrupted, and that interrupt handler might contain an RCU read-side critical section, which might invoke rcu_read_unlock_special(). In the strict KCSAN mode of operation used by RCU, this constitutes a data race on the ->defer_qs_iw_pending field. This commit therefore disables interrupts across the portion of the rcu_preempt_deferred_qs_handler() that updates the ->defer_qs_iw_pending field. This suffices because this handler is not a fast path.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于对rcu_data结构中的defer_qs_iw_pending字段缺乏保护，可能导致数据竞争。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 0864f057b050bc6dd68106b3185e02db5140012d ~ 74f58f382a7c8333f8d09701aefaa25913bdbe0e -
Linux Linux 5.3 -

II. Public POCs for CVE-2025-39749

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III. Intelligence Information for CVE-2025-39749

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Same Patch Batch · Linux · 2025-09-11 · 54 CVEs total

CVE-2025-39758 9.8 CRITICAL RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages
CVE-2025-39761 8.8 HIGH wifi: ath12k: Decrement TID on RX peer frag setup error handling
CVE-2025-39750 8.8 HIGH wifi: ath12k: Correct tid cleanup when tid setup fails
CVE-2025-39790 8.4 HIGH bus: mhi: host: Detect events pointing to unexpected TREs
CVE-2025-39779 7.8 HIGH btrfs: subpage: keep TOWRITE tag until folio is cleaned
CVE-2025-39791 7.8 HIGH dm: dm-crypt: Do not partially accept write BIOs with zoned targets
CVE-2025-39780 7.8 HIGH sched/ext: Fix invalid task state transitions on class switch
CVE-2025-39785 7.8 HIGH drm/hisilicon/hibmc: fix irq_request()'s irq name variable is local
CVE-2025-39786 7.8 HIGH iio: adc: ad7173: fix channels index for syscalib_mode
CVE-2025-39787 7.8 HIGH soc: qcom: mdt_loader: Ensure we don't read past the ELF header
CVE-2025-39740 7.8 HIGH drm/xe/migrate: prevent potential UAF
CVE-2025-39770 7.5 HIGH net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM
CVE-2025-39738 7.3 HIGH btrfs: do not allow relocation of partially dropped subvolumes
CVE-2025-39789 7.3 HIGH crypto: x86/aegis - Add missing error checks
CVE-2025-39776 7.0 HIGH mm/debug_vm_pgtable: clear page table entries at destroy_args()
CVE-2025-39764 netfilter: ctnetlink: remove refcounting in expectation dumpers
CVE-2025-39768 net/mlx5: HWS, fix complex rules rehash error flow
CVE-2025-39773 net: bridge: fix soft lockup in br_multicast_query_expired()
CVE-2025-39772 drm/hisilicon/hibmc: fix the hibmc loaded failed bug
CVE-2025-39769 bnxt_en: Fix lockdep warning during rmmod

Showing top 20 of 54 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-39749

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