btrfs: always wait for ordered extents to avoid OE races

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-90264
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:17:22 UTC
Updated2026-09-17 17:17:22 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: btrfs: always wait for ordered extents to avoid OE races [BUG] Syzbot reported a bug that there can be conflicting OEs for the same range: BTRFS critical (device loop4): panic in insert_ordered_extent:264: overlapping ordered extents, existing oe file_offset 16384 num_bytes 430080 flags 0x1089, new oe file_offset 16384 num_bytes 430080 flags 0x80 (errno=-17 Object alrea[ 179.162726][ T6897] BTRFS critical (device loop4): panic in insert_ordered_extent:264: overlapping ordered extents, existing oe file_offset 16384 num_bytes 430080 flags 0x1089, new oe file_offset 16384 num_bytes 430080 flags 0x80 (errno=-17 Object already exists) ------------[ cut here ]------------ kernel BUG at fs/btrfs/ordered-data.c:264! Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 RIP: 0010:btrfs_alloc_ordered_extent+0x943/0xad0 Call Trace: <TASK> cow_file_range+0x744/0x12a0 fallback_to_cow+0x5ea/0xa00 run_delalloc_nocow+0x110c/0x17a0 btrfs_run_delalloc_range+0xbe4/0x1c20 writepage_delalloc+0x104d/0x1ba0 btrfs_writepages+0x1667/0x28b0 do_writepages+0x338/0x560 filemap_fdatawrite_range+0x1f2/0x300 btrfs_fdatawrite_range+0x54/0xf0 btrfs_direct_write+0x6a0/0xc30 btrfs_do_write_iter+0x329/0x790 do_iter_readv_writev+0x624/0x8d0 vfs_writev+0x34c/0x990 __se_sys_pwritev2+0x17a/0x2a0 do_syscall_64+0x174/0x580 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> ---[ end trace 0000000000000000 ]--- [CAUSE] Since commit ff66fe666233 ("btrfs: fix incorrect buffered IO fallback for append direct writes"), if the direct IO finished short, we will revert the isize back to the original one, so that append writes can be respected during the buffered fallback. Normally we rely on lock_and_cleanup_extent_if_need() function during buffered writeback to wait for any existing ordered extents. But that ordered extent waiting only happens if the start_pos is inside the isize. Since we have reverted the isize during failed direct IO, we will not wait for any ordered extents. This means we can have a race where the direct IO OE is still in the tree, finished but not yet removed, then we're inserting the OE for the buffered write, causing the above crash. [FIX] Make the OE wait to be unconditional, to handle the reverted isize situation. And since lock_and_cleanup_extent_if_need() now either lock the extents or return -EAGAIN, also remove the branches that handles no-extent-locked cases, and rename it to remove the "_if_need" suffix. The following micro benchmark shows the runtime difference for btrfs_buffered_write(), doing `xfs_io -f -c "pwrite 0 1m"` workload, all values are the average runtime in nano seconds. function runtime | before | after -----------------------------------+-------------+--------------- lock_and_cleanup_extent_if_need() | 58.2 | 183.0 btrfs_buffered_write() | 2115.6 | 2973.3 The overall runtime of btrfs_buffered_write() is still pretty tiny (still less than 3 micro seconds), I'd say the extra cost is still acceptable. An alternative to fix this problem is to wait ordered extents during iomap_end() where the isize revert is done. But that solution will break nowait requirement, as if a nowait direct IO finished short, we have to wait for the OEs unconditionally or the next append buffered IO can still hit the same problem. So here we have to move the wait cost to buffered write, but at least the code is slightly more streamline.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected c3a3d3986719026c85950bfa6f41a251fc46e16f 58ce50b1802a446d3b26df1b9c58be1ab8913d0e git Not specified
CNA Linux Linux affected ff66fe6662330226b3f486014c375538d91c44aa aaac9b352f7f53f5d2f7e58e612d67d2a2bf7094 git Not specified
CNA Linux Linux affected ff66fe6662330226b3f486014c375538d91c44aa ec78575dde998c21be7e0cb2503b5620f34b6255 git Not specified
CNA Linux Linux affected 4b5875cbb85dbf4d11385eb0a7a589c086d76d42 git Not specified
CNA Linux Linux affected 10b1abc1d0c8ae25c2b9ac465515717c68ffff05 git Not specified
CNA Linux Linux affected 097b159d43407b4ea0e5d14ae58a3bbfa5865a24 git Not specified
CNA Linux Linux affected ccd5c23122b01de646c80485e2fadac82d1aab62 git Not specified
CNA Linux Linux affected b8df7f486a4617d3096b8fa27148cfa54b1d6a8d git Not specified
CNA Linux Linux affected 6.18.40 6.18.52 semver Not specified
CNA Linux Linux affected 5.15.212 5.16 semver Not specified
CNA Linux Linux affected 6.1.178 6.2 semver Not specified
CNA Linux Linux affected 6.6.145 6.7 semver Not specified
CNA Linux Linux affected 6.12.97 6.13 semver Not specified
CNA Linux Linux affected 7.1.4 7.2 semver Not specified
CNA Linux Linux affected 7.2 Not specified
CNA Linux Linux unaffected 7.2 semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ec78575dde998c21be7e0cb2503b5620f34b6255 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/58ce50b1802a446d3b26df1b9c58be1ab8913d0e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/aaac9b352f7f53f5d2f7e58e612d67d2a2bf7094 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report