# CVE-2026-46031: net: ks8851: Reinstate disabling of BHs around IRQ handler

CVE-2026-46031 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-46031, released May 27, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-46031
- Priority: High
- CVSS: 7.5 (Moderate)
- EPSS: 0.0037
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 27, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-46031

## Description

In the Linux kernel, the following vulnerability has been resolved:  net: ks8851: Reinstate disabling of BHs around IRQ handler  If the driver executes ks8851_irq() AND a TX packet has been sent, then the driver enables TX queue via netif_wake_queue() which schedules TX softirq to queue packets for this device.  If CONFIG_PREEMPT_RT=y is set AND a packet has also been received by the MAC, then ks8851_rx_pkts() calls netdev_alloc_skb_ip_align() to allocate SKBs for the received packets. If netdev_alloc_skb_ip_align() is called with BH enabled, then local_bh_enable() at the end of netdev_alloc_skb_ip_align() will trigger the pending softirq processing, which may ultimately call the .xmit callback ks8851_start_xmit_par(). The ks8851_start_xmit_par() will try to lock struct ks8851_net_par .lock spinlock, which is already locked by ks8851_irq() from which ks8851_start_xmit_par() was called. This leads to a deadlock, which is reported by the kernel, including a trace listed below.  If CONFIG_PREEMPT_RT is not set, then since commit 0913ec336a6c0 ("net: ks8851: Fix deadlock with the SPI chip variant") the deadlock can also be triggered without received packet in the RX FIFO. The pending softirqs will be processed on return from spin_unlock_bh(&ks->statelock) in ks8851_irq(), which triggers the deadlock as well.  Fix the problem by disabling BH around critical sections, including the IRQ handler, thus preventing the net_tx_action() softirq from triggering during these critical sections. The net_tx_action() softirq is triggered once BH are re-enabled and at the end of the IRQ handler, once all the other IRQ handler actions have been completed.   __schedule from schedule_rtlock+0x1c/0x34  schedule_rtlock from rtlock_slowlock_locked+0x548/0x904  rtlock_slowlock_locked from rt_spin_lock+0x60/0x9c  rt_spin_lock from ks8851_start_xmit_par+0x74/0x1a8  ks8851_start_xmit_par from netdev_start_xmit+0x20/0x44  netdev_start_xmit from dev_hard_start_xmit+0xd0/0x188  dev_hard_start_xmit from sch_direct_xmit+0xb8/0x25c  sch_direct_xmit from __qdisc_run+0x1f8/0x4ec  __qdisc_run from qdisc_run+0x1c/0x28  qdisc_run from net_tx_action+0x1f0/0x268  net_tx_action from handle_softirqs+0x1a4/0x270  handle_softirqs from __local_bh_enable_ip+0xcc/0xe0  __local_bh_enable_ip from __alloc_skb+0xd8/0x128  __alloc_skb from __netdev_alloc_skb+0x3c/0x19c  __netdev_alloc_skb from ks8851_irq+0x388/0x4d4  ks8851_irq from irq_thread_fn+0x24/0x64  irq_thread_fn from irq_thread+0x178/0x28c  irq_thread from kthread+0x12c/0x138  kthread from ret_from_fork+0x14/0x28

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.176-1 | [DEBIAN-CVE-2026-46031](https://patchblox.com/security/data/fix/linux/debian-cve-2026-46031.md) | May 27, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.86-1 | [DEBIAN-CVE-2026-46031](https://patchblox.com/security/data/fix/linux/debian-cve-2026-46031.md) | May 27, 2026 |
| Linux | linux Debian 14 | 7.0.4-1 | [DEBIAN-CVE-2026-46031](https://patchblox.com/security/data/fix/linux/debian-cve-2026-46031.md) | May 27, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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