{"id":"CVE-2026-74572","state":"PUBLISHED","title":"btrfs: zoned: fix deadlock between metadata writeback and transaction commit","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zoned: fix deadlock between metadata writeback and transaction commit\n\nWhen writing out metadata extent buffers in a zoned filesystem,\nbtree_writepages() holds fs_info->zoned_meta_io_lock across the whole\nwriteback loop, including the call to btrfs_check_meta_write_pointer() ->\ncheck_bg_is_active().\n\nFor the tree-log block group, check_bg_is_active() may fail to activate\nthe zone and fall back to btrfs_zone_finish_one_bg() to free an active\nzone. That path waits for the running transaction to commit while still\nholding zoned_meta_io_lock, but the committer needs that same lock to\nwrite out the tree extents, so the two tasks deadlock:\n\n  Task A (kworker, metadata writeback)      Task B (fsstress, transaction commit)\n  ------------------------------------      -------------------------------------\n  wb_workfn()                               btrfs_commit_transaction(T)\n   btree_writepages()                        btrfs_write_and_wait_transaction()\n    btrfs_zoned_meta_io_lock()                btrfs_write_marked_extents()\n    btrfs_check_meta_write_pointer()           btree_writepages()\n     check_bg_is_active() [treelog_bg]          btrfs_zoned_meta_io_lock()\n      btrfs_zone_finish_one_bg()               <blocks on zoned_meta_io_lock,\n       btrfs_zone_finish()                      held by Task A>\n        do_zone_finish()\n         btrfs_inc_block_group_ro()\n          btrfs_wait_for_commit()\n           <blocks waiting for commit\n            of transaction T, done by\n            Task B>\n\nThe sibling branch in check_bg_is_active() already drops zoned_meta_io_lock\naround do_zone_finish() for this exact reason. Do the same in the tree-log\nbranch: release the lock around btrfs_zone_finish_one_bg() and re-acquire\nit afterwards. The lock only protects fs_info->active_{meta,system}_bg,\nwhich this branch does not touch, and ctx->zoned_bg keeps a reference to\nthe block group across the unlock, so nothing is lost while the lock\nis dropped.\n\nThis hang occasionally reproduces with fstests generic/475 on a zoned\nbtrfs filesystem.","publishedAt":"2026-08-15T12:28:11.328Z","updatedAt":"2026-10-16T19:05:56.826Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"c3320873e0c04ce7b746fc8fe948f07bbbbdec33","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"deddd28fd83c264ee2ff5cd6b34449a9f1be6112","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"75859a7cd77cd2ddaddbcb963e3fcd34738953af","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"1ebe51c29fa9755d5b2fea28727c051117907cf8","versionType":"git"},{"version":"fca3a1cd3ba47f1815e0c0fcdc9aafaf02ee0a75","status":"affected","versionType":"git"},{"version":"6.5.5","status":"affected","lessThan":"6.6","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/zoned.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"6.6.151","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.103","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.44","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.8","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/zoned.c"]}],"references":["https://git.kernel.org/stable/c/18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd","https://git.kernel.org/stable/c/c3320873e0c04ce7b746fc8fe948f07bbbbdec33","https://git.kernel.org/stable/c/deddd28fd83c264ee2ff5cd6b34449a9f1be6112","https://git.kernel.org/stable/c/75859a7cd77cd2ddaddbcb963e3fcd34738953af","https://git.kernel.org/stable/c/1ebe51c29fa9755d5b2fea28727c051117907cf8"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74572.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74572","state":"PUBLISHED","datePublished":"2026-08-15T12:28:11.328Z","dateUpdated":"2026-10-16T19:05:56.826Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.917Z"},"containers":{"cna":{"title":"btrfs: zoned: fix deadlock between metadata writeback and transaction commit","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zoned: fix deadlock between metadata writeback and transaction commit\n\nWhen writing out metadata extent buffers in a zoned filesystem,\nbtree_writepages() holds fs_info->zoned_meta_io_lock across the whole\nwriteback loop, including the call to btrfs_check_meta_write_pointer() ->\ncheck_bg_is_active().\n\nFor the tree-log block group, check_bg_is_active() may fail to activate\nthe zone and fall back to btrfs_zone_finish_one_bg() to free an active\nzone. That path waits for the running transaction to commit while still\nholding zoned_meta_io_lock, but the committer needs that same lock to\nwrite out the tree extents, so the two tasks deadlock:\n\n  Task A (kworker, metadata writeback)      Task B (fsstress, transaction commit)\n  ------------------------------------      -------------------------------------\n  wb_workfn()                               btrfs_commit_transaction(T)\n   btree_writepages()                        btrfs_write_and_wait_transaction()\n    btrfs_zoned_meta_io_lock()                btrfs_write_marked_extents()\n    btrfs_check_meta_write_pointer()           btree_writepages()\n     check_bg_is_active() [treelog_bg]          btrfs_zoned_meta_io_lock()\n      btrfs_zone_finish_one_bg()               <blocks on zoned_meta_io_lock,\n       btrfs_zone_finish()                      held by Task A>\n        do_zone_finish()\n         btrfs_inc_block_group_ro()\n          btrfs_wait_for_commit()\n           <blocks waiting for commit\n            of transaction T, done by\n            Task B>\n\nThe sibling branch in check_bg_is_active() already drops zoned_meta_io_lock\naround do_zone_finish() for this exact reason. Do the same in the tree-log\nbranch: release the lock around btrfs_zone_finish_one_bg() and re-acquire\nit afterwards. The lock only protects fs_info->active_{meta,system}_bg,\nwhich this branch does not touch, and ctx->zoned_bg keeps a reference to\nthe block group across the unlock, so nothing is lost while the lock\nis dropped.\n\nThis hang occasionally reproduces with fstests generic/475 on a zoned\nbtrfs filesystem."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"c3320873e0c04ce7b746fc8fe948f07bbbbdec33","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"deddd28fd83c264ee2ff5cd6b34449a9f1be6112","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"75859a7cd77cd2ddaddbcb963e3fcd34738953af","versionType":"git"},{"version":"13bb483d32abb6f8ebd40141d87eb68f11cc2dd2","status":"affected","lessThan":"1ebe51c29fa9755d5b2fea28727c051117907cf8","versionType":"git"},{"version":"fca3a1cd3ba47f1815e0c0fcdc9aafaf02ee0a75","status":"affected","versionType":"git"},{"version":"6.5.5","status":"affected","lessThan":"6.6","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/zoned.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"6.6.151","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.103","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.44","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.8","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/zoned.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/18577e77c2c8adaadf1f7c6e9bcd1c0b14e5dcdd"},{"url":"https://git.kernel.org/stable/c/c3320873e0c04ce7b746fc8fe948f07bbbbdec33"},{"url":"https://git.kernel.org/stable/c/deddd28fd83c264ee2ff5cd6b34449a9f1be6112"},{"url":"https://git.kernel.org/stable/c/75859a7cd77cd2ddaddbcb963e3fcd34738953af"},{"url":"https://git.kernel.org/stable/c/1ebe51c29fa9755d5b2fea28727c051117907cf8"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - On storage servers exporting a zoned btrfs volume via nfsd or ksmbd, remote client write/fsync I/O reaches btrfs_commit_transaction() and btree_writepages() on the server kernel without any local syscall access.\nAC:L - The attacker controls both deadlock participants by driving concurrent metadata dirtying/writeback and transaction commits (reproduced with fsstress/fstests generic/475); the kworker writeback side is a direct result of attacker-generated btree dirty pages.\nPR:N - Exploitation requires only network write access to an NFS or SMB export of the zoned btrfs filesystem; no local account, capability, or init-namespace privilege is needed when the export permits client writes.\nUI:N - The deadlock is triggered entirely by the attacker's own concurrent write and sync I/O; no victim must mount a filesystem, open a file, or perform any interactive action.\nS:U - The mutex deadlock freezes btrfs metadata I/O within the same host kernel security authority; it does not cross a VM, IOMMU, or sandbox boundary.\nC:N - This is a lock-ordering deadlock with no memory corruption, out-of-bounds access, use-after-free, or information disclosure of any kind.\nI:N - The bug causes tasks to block indefinitely on locks but does not corrupt, modify, or overwrite any data or enable arbitrary writes or code execution.\nA:H - The circular wait between zoned_meta_io_lock and btrfs_wait_for_commit() permanently hangs metadata writeback and transaction commit, freezing all I/O on the affected zoned btrfs filesystem."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:48:51.651Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.6.151"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.12.103"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.18.44"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"7.1.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.5.5"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74572","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T19:00:32.799131Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:05:56.826Z"}}]}}}