GHSA-279Q-P928-6329
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In 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").
{
"affected": [],
"aliases": [
"CVE-2026-90096"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:01Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: invalidate the correct range after O_APPEND direct write\n\nfuse_direct_write_iter() captures pos before generic_write_checks(),\nwhich moves ki_pos to EOF for O_APPEND writes:\n\n fuse_direct_write_iter()\n {\n pos = iocb-\u003eki_pos; /* 0 (user-supplied) */\n generic_write_checks(); /* ki_pos -\u003e EOF */\n fuse_direct_io(); /* writes at EOF, correct */\n invalidate(pos, pos + res); /* [0, res) -- wrong */\n }\n\nThe post-write invalidation targets a stale range instead of the\nactual written range at EOF.\n\nThis can cause data inconsistency when the file size is not\npage-aligned. The tail page straddling EOF has a valid portion\nbefore EOF that concurrent readers can fault back in during the\nDIO write window:\n\n Tail page (file size X not page-aligned):\n\n page_start X (EOF) page_end\n |--- valid data ----|-- stale --|\n\n CPU0 (O_APPEND DIO writer) CPU1 (buffered reader)\n -------------------------- ----------------------\n invalidate [X, X+len)\n tail page evicted\n FUSE_WRITE in flight ...\n read [page_start, X)\n tail page re-faulted\n [X, page_end) = stale\n FUSE_WRITE completes\n i_size = X + len\n invalidate [0, len) \u003c- WRONG\n tail page still cached\n read [X, X+len)\n hits stale tail page\n returns old data\n\nFix by reading pos back from iocb-\u003eki_pos after generic_write_checks(),\nas generic_file_direct_write() does.\n\nAlso fix a typo in the comment (\"may have\" -\u003e \"may have competed\").",
"id": "GHSA-279q-p928-6329",
"modified": "2026-09-17T18:31:50Z",
"published": "2026-09-17T18:31:50Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90096"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/26d7e1f5c407b5859122b5cd47d7ebbf4b4c1cd2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/833963069adf86dcbdffd4e7d7b3171f95070b77"
}
],
"schema_version": "1.4.0",
"severity": []
}
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