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

Status: published. Published: 2026-04-24. Updated: 2026-11-05.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < 81f44ed8c3f54abb7561ece774ea4cca5070b2f2 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < f50e7c325ab1207fe941555bcff659f6d7050572 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < 9467d360be70e6ee55b0c1cd2a1f1424f57b5b85 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < 47fa09fe7f3e09df28a51cb2cbd8f5d2f7f6edc1 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < add4982510f3b7c318a2dd7438bdc9c63171e753 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < 2d6965581e164fa2ba3f7652ddae5535f6336576 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < 4f71c8ba2dc009042493021d94a9718fbe2ebf27 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < 383f7fec0de8cee1cf7ae1f9d9f14044a61f10f9 (affected, git); ≥ cafe563591446cf80bfbc2fe3bc72a2e36cf1060; < fec114a98b8735ee89c75216c45a78e28be0f128 (affected, git). Source: CNA: Linux
- Linux / Linux: 3.10 (affected); ≥ 0; < 3.10 (unaffected, semver); ≥ 5.10.258; ≤ 5.10.* (unaffected, semver); ≥ 5.15.209; ≤ 5.15.* (unaffected, semver); ≥ 6.1.175; ≤ 6.1.* (unaffected, semver); ≥ 6.6.136; ≤ 6.6.* (unaffected, semver); ≥ 6.12.83; ≤ 6.12.* (unaffected, semver); ≥ 6.18.24; ≤ 6.18.* (unaffected, semver); ≥ 6.19.14; ≤ 6.19.* (unaffected, semver); ≥ 7.0.1; ≤ 7.0.* (unaffected, semver); ≥ 7.1; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 TM MFP - GNU/Linux subsystem: ≥ 0; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.13% as of 2026-11-05; percentile 2.74%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/81f44ed8c3f54abb7561ece774ea4cca5070b2f2 (CNA: Linux)

- https://git.kernel.org/stable/c/f50e7c325ab1207fe941555bcff659f6d7050572 (CNA: Linux)

- https://git.kernel.org/stable/c/9467d360be70e6ee55b0c1cd2a1f1424f57b5b85 (CNA: Linux)

- https://git.kernel.org/stable/c/47fa09fe7f3e09df28a51cb2cbd8f5d2f7f6edc1 (CNA: Linux)

- https://git.kernel.org/stable/c/add4982510f3b7c318a2dd7438bdc9c63171e753 (CNA: Linux)

- https://git.kernel.org/stable/c/2d6965581e164fa2ba3f7652ddae5535f6336576 (CNA: Linux)

- https://git.kernel.org/stable/c/4f71c8ba2dc009042493021d94a9718fbe2ebf27 (CNA: Linux)

- https://git.kernel.org/stable/c/383f7fec0de8cee1cf7ae1f9d9f14044a61f10f9 (CNA: Linux)

- https://git.kernel.org/stable/c/fec114a98b8735ee89c75216c45a78e28be0f128 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-31580; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-31580; retrieved 2026-11-05; source updated Not reported

Revision: 77ff75e30b6630e5b3b5d9087a5d484aa45bc34e18a5d1d5f9a2105645ae2174

Canonical: https://y2.dev/cve/CVE-2026-31580

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