{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-64378", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-64378", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-07-25T08:50:29.006Z", "updatedAt": "2026-10-19T20:38:25.561Z", "importedAt": "2026-10-24T01:58:25.636Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: fix race between cgroup_writeback_umount() and inode_switch_wbs()\n\nWhen a container exits, the following BUG_ON() is occasionally triggered:\n\n==================================================================\n VFS: Busy inodes after unmount of sdb (ext4)\n ------------[ cut here ]------------\n kernel BUG at fs/super.c:695!\n CPU: 3 PID: 6 Comm: containerd-shim Tainted: G OE K 6.6 #1\n pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)\n pc : generic_shutdown_super+0xf0/0x100\n lr : generic_shutdown_super+0xf0/0x100\n Call trace:\n generic_shutdown_super+0xf0/0x100\n kill_block_super+0x20/0x48\n ext4_kill_sb+0x28/0x60\n deactivate_locked_super+0x54/0x130\n deactivate_super+0x84/0xa0\n cleanup_mnt+0xa4/0x140\n __cleanup_mnt+0x18/0x28\n task_work_run+0x78/0xe0\n do_notify_resume+0x204/0x240\n==================================================================\n\nThe root cause is a race between cgroup_writeback_umount() and\ninode_switch_wbs()/cleanup_offline_cgwb(). There is a window between\ninode_prepare_wbs_switch() returning true and the subsequent\nwb_queue_isw() call. Following is the process that triggers the issue:\n\n CPU A (umount) | CPU B (writeback)\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n inode_switch_wbs/cleanup_offline_cgwb\n atomic_inc(&isw_nr_in_flight)\n inode_prepare_wbs_switch\n -> passes SB_ACTIVE check\n __iget(inode)\n generic_shutdown_super\n sb->s_flags &= ~SB_ACTIVE\n cgroup_writeback_umount(sb)\n smp_mb()\n atomic_read(&isw_nr_in_flight)\n rcu_barrier()\n -> no pending RCU callbacks\n flush_workqueue(isw_wq)\n -> nothing queued, returns\n evict_inodes(sb)\n -> Inode skipped as isw still holds a ref.\n sop->put_super(sb)\n /* destroys percpu counters */\n -> VFS: Busy inodes after unmount!\n wb_queue_isw()\n queue_work(isw_wq, ...)\n /* later in work function */\n inode_switch_wbs_work_fn\n process_inode_switch_wbs\n iput() -> evict\n percpu_counter_dec() // UAF!\n\nFix this by extending the RCU read-side critical section in\ninode_switch_wbs() and cleanup_offline_cgwb() to cover from\ninode_prepare_wbs_switch() through wb_queue_isw(). Since there is\nno sleep in this window, rcu_read_lock() can be used. Then add a\nsynchronize_rcu() in cgroup_writeback_umount() before the existing\nrcu_barrier(), so that all in-flight switchers that have passed the\nSB_ACTIVE check have completed queue_work() before flush_workqueue()\nis called.\n\nThe existing rcu_barrier() is intentionally retained so this fix can\nbe backported unchanged to stable kernels (5.10.y, 6.6.y, ...) that\nstill queue switches via queue_rcu_work(). It is a no-op on current\nmainline (since commit e1b849cfa6b6 (\"writeback: Avoid contention on\nwb->list_lock when switching inodes\")) and is removed in a follow-up\npatch.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "087d5b8b501c570f84bf655164e6698c3ce146e0" }, { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "3c9c9648f77e4d14e50676bc51c2174ba9c8d361" }, { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "5c3265f3252b2ee50707adaaa3f9bd0df3df72de" }, { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "c923cc3cb5cd8945ceaf08252754110643446593" }, { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "685fc15a410885b6d4dee64de0dce721b9428b12" }, { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "53eeaf4d63068dbc7708b0c7adb20151c812feca" }, { "version": "a1a0e23e49037c23ea84bc8cc146a03584d13577", "status": "affected", "versionType": "git", "lessThan": "cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d" }, { "version": "c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339", "status": "affected", "versionType": "git" }, { "version": "4.4.5", "status": "affected", "versionType": "semver", "lessThan": "4.5" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "4.5", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "4.5" }, { "version": "5.10.261", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "6.1.178", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.145", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.96", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.39", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.1.4", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.1.*" }, { "version": "7.2", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }