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CVE-2026-31580: bcache: fix cached_dev.sb_bio use-after-free and crash

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-24 · updated 2026-10-15
• Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: bcache: fix cached_dev.sb_bio use-after-free and crash In our production environment, we have received multiple crash reports regarding libceph, which have caught our attention: ``` [6888366.280350] Call Trace: [6888366.280452] blk_update_request+0x14e/0x370 [6888366.280561] blk_mq_end_request+0x1a/0x130 [6888366.280671] rbd_img_handle_request+0x1a0/0x1b0 [rbd] [6888366.280792] rbd_obj_handle_request+0x32/0x40 [rbd] [6888366.280903] __complete_request+0x22/0x70 [libceph] [6888366.281032] osd_dispatch+0x15e/0xb40 [libceph] [6888366.281164] ? inet_recvmsg+0x5b/0xd0 [6888366.281272] ? ceph_tcp_recvmsg+0x6f/0xa0 [libceph] [6888366.281405] ceph_con_process_message+0x79/0x140 [libceph] [6888366.281534] ceph_con_v1_try_read+0x5d7/0xf30 [libceph] [6888366.281661] ceph_con_workfn+0x329/0x680 [libceph] ``` After analyzing the coredump file, we found that the address of dc->sb_bio has been freed. We know that cached_dev is only freed when it is stopped. Since sb_bio is a part of struct cached_dev, rather than an alloc every time. If the device is stopped while writing to the superblock, the released address will be accessed at endio. This patch hopes to wait for sb_write to complete in cached_dev_free. It should be noted that we analyzed the cause of the problem, then tell all details to the QWEN and adopted the modifications it made.

Affected products

• Linux kernel: before 6.6.136; from 6.12 before 6.12.83; from 6.13 before 6.18.24; from 6.19 before 6.19.14; from 7.0 before 7.0.1 — fixed in 6.12.83, 6.18.24, 6.19.14, 6.6.136, 7.0.1

How to fix

Upgrade to a fixed version: Linux kernel 6.12.83, 6.18.24, 6.19.14, 6.6.136. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/2d6965581e164fa2ba3f7652ddae5535f6336576
• https://git.kernel.org/stable/c/383f7fec0de8cee1cf7ae1f9d9f14044a61f10f9
• https://git.kernel.org/stable/c/47fa09fe7f3e09df28a51cb2cbd8f5d2f7f6edc1
• https://git.kernel.org/stable/c/4f71c8ba2dc009042493021d94a9718fbe2ebf27
• https://git.kernel.org/stable/c/81f44ed8c3f54abb7561ece774ea4cca5070b2f2
• https://git.kernel.org/stable/c/9467d360be70e6ee55b0c1cd2a1f1424f57b5b85
• https://git.kernel.org/stable/c/add4982510f3b7c318a2dd7438bdc9c63171e753
• https://git.kernel.org/stable/c/f50e7c325ab1207fe941555bcff659f6d7050572
• https://git.kernel.org/stable/c/fec114a98b8735ee89c75216c45a78e28be0f128
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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