Description

In the Linux kernel, the following vulnerability has been resolved: ceph: do not propagate page array emplacement errors as batch errors When fscrypt is enabled, move_dirty_folio_in_page_array() may fail because it needs to allocate bounce buffers to store the encrypted versions of each folio. Each folio beyond the first allocates its bounce buffer with GFP_NOWAIT. Failures are common (and expected) under this allocation mode; they should flush (not abort) the batch. However, ceph_process_folio_batch() uses the same `rc` variable for its own return code and for capturing the return codes of its routine calls; failing to reset `rc` back to 0 results in the error being propagated out to the main writeback loop, which cannot actually tolerate any errors here: once `ceph_wbc.pages` is allocated, it must be passed to ceph_submit_write() to be freed. If it survives until the next iteration (e.g. due to the goto being followed), ceph_allocate_page_array()'s BUG_ON() will oops the worker. Note that this failure mode is currently masked due to another bug (addressed next in this series) that prevents multiple encrypted folios from being selected for the same write. For now, just reset `rc` when redirtying the folio to prevent errors in move_dirty_folio_in_page_array() from propagating. Note that move_dirty_folio_in_page_array() is careful never to return errors on the first folio, so there is no need to check for that. After this change, ceph_process_folio_batch() no longer returns errors; its only remaining failure indicator is `locked_pages == 0`, which the caller already handles correctly.

Affected Products 2

References 3

• git.kernel.org https://git.kernel.org/stable/c/4c0d84c788d89c167abf0bf84fd37890c4c84f08
  Patch
• git.kernel.org https://git.kernel.org/stable/c/707104682e3c163f7c14cdd6b07a3e95fb374759
  Patch
• git.kernel.org https://git.kernel.org/stable/c/746840c87d76b614b14d9337c466ff022fc49823
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/4c0d84c788d89c167abf0bf84fd37890c4c84f08
  Patch
• git.kernel.org https://git.kernel.org/stable/c/707104682e3c163f7c14cdd6b07a3e95fb374759
  Patch
• git.kernel.org https://git.kernel.org/stable/c/746840c87d76b614b14d9337c466ff022fc49823
  Patch