netfs: clear post-EOF pagecache when extending a file via write

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98844
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:17:38 UTC
Updated2026-10-19 10:19:48 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: netfs: clear post-EOF pagecache when extending a file via write Fix netfs to erase the contents of a hole created after the EOF by an ordinary write if dirty data has been previously left there by writes through an mmapped region. Neither the buffered nor the unbuffered/DIO write path clears that stale pagecache. Zero the tail of the folio straddling the EOF before an extending write. That is the only folio that can hold data written past the EOF through an mmap, as pages wholly beyond the EOF can't be faulted in. The folio is zeroed rather than dropped so a concurrent extending write can't lose data. Both write paths downgrade the i_rwsem to shared, so extending writes can run concurrently and the i_size read by the caller may be stale by the time the folio is locked. Re-read i_size under the folio lock and clamp the zeroed range up to it, so a racing write that already put data into the folio isn't clobbered. Wait for any writeback on the folio to finish before zeroing it so that the pagecache isn't modified while it may still be read by the transport during transmission. Honour IOCB_NOWAIT by returning -EAGAIN rather than blocking on the folio lock, on writeback, or in folio_mkclean()'s rmap walk when the folio is mapped. truncate_pagecache() can't be used here: it must be called with the i_rwsem held exclusively, but these write paths only hold it shared, and it would block unconditionally, breaking IOCB_NOWAIT. Callers that hold i_rwsem exclusively for the whole resize (truncate, setattr, fallocate, clone) exclude any genuine concurrent buffered writer, so staleness can instead be decided from the folio's dirty state, as pagecache_isize_extended() already does for filesystems that serialise writes against truncate/setattr via a single i_rwsem. Export netfs_clear_stale_post_isize() helper to handle such case. The helper is required by the CIFS client to fix generic/363.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 153a9961b551101cd38e94e26cd92fbfd198b19b f8f7d86b3537e885ee620898a38b749fba8a8456 git Not specified
CNA Linux Linux affected 153a9961b551101cd38e94e26cd92fbfd198b19b 98f6a4589e0f5f6cf819b8dd45605efc481c06ce git Not specified
CNA Linux Linux affected 153a9961b551101cd38e94e26cd92fbfd198b19b a7036a73671fc83d299bc770710fe996d9fef9ca git Not specified
CNA Linux Linux affected 153a9961b551101cd38e94e26cd92fbfd198b19b 69bf14300b50631e7c2271289d347bbd1b19a06c git Not specified
CNA Linux Linux affected 6.8 Not specified
CNA Linux Linux unaffected 6.8 semver Not specified
CNA Linux Linux unaffected 6.12.113 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.56 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.10 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/98f6a4589e0f5f6cf819b8dd45605efc481c06ce 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a7036a73671fc83d299bc770710fe996d9fef9ca 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/69bf14300b50631e7c2271289d347bbd1b19a06c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f8f7d86b3537e885ee620898a38b749fba8a8456 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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