fuse: invalidate the correct range after O_APPEND direct write

Summary

In the Linux kernel, the following vulnerability has been resolved: fuse: invalidate the correct range after O_APPEND direct write fuse_direct_write_iter() captures pos before generic_write_checks(), which moves ki_pos to EOF for O_APPEND writes: fuse_direct_write_iter() { pos = iocb->ki_pos; /* 0 (user-supplied) */ generic_write_checks(); /* ki_pos -> EOF */ fuse_direct_io(); /* writes at EOF, correct */ invalidate(pos, pos + res); /* [0, res) -- wrong */ } The post-write invalidation targets a stale range instead of the actual written range at EOF. This can cause data inconsistency when the file size is not page-aligned. The tail page straddling EOF has a valid portion before EOF that concurrent readers can fault back in during the DIO write window: Tail page (file size X not page-aligned): page_start X (EOF) page_end |--- valid data ----|-- stale --| CPU0 (O_APPEND DIO writer) CPU1 (buffered reader) -------------------------- ---------------------- invalidate [X, X+len) tail page evicted FUSE_WRITE in flight ... read [page_start, X) tail page re-faulted [X, page_end) = stale FUSE_WRITE completes i_size = X + len invalidate [0, len) <- WRONG tail page still cached read [X, X+len) hits stale tail page returns old data Fix by reading pos back from iocb->ki_pos after generic_write_checks(), as generic_file_direct_write() does. Also fix a typo in the comment ("may have" -> "may have competed").

Timeline

1. Sep 17, 2026, 4:06 PM UTCCVE published
2. Oct 19, 2026, 8:57 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 2b0408d0284f4ff376cf5610fa8c9905e93c2541 · fixed in 833963069adf86dcbdffd4e7d7b3171f95070b77; From 2b0408d0284f4ff376cf5610fa8c9905e93c2541 · fixed in 26d7e1f5c407b5859122b5cd47d7ebbf4b4c1cd2

• Linux Linux

  7.2

• KernelLinux

  From 7.2.0 · fixed in 7.2.6

References 2