{ "affected": [ { "ranges": [ { "events": [ { "introduced": "a1a0e23e49037c23ea84bc8cc146a03584d13577" }, { "fixed": "087d5b8b501c570f84bf655164e6698c3ce146e0" }, { "fixed": "3c9c9648f77e4d14e50676bc51c2174ba9c8d361" }, { "fixed": "5c3265f3252b2ee50707adaaa3f9bd0df3df72de" }, { "fixed": "c923cc3cb5cd8945ceaf08252754110643446593" }, { "fixed": "685fc15a410885b6d4dee64de0dce721b9428b12" }, { "fixed": "53eeaf4d63068dbc7708b0c7adb20151c812feca" }, { "fixed": "cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" }, { "events": [ { "introduced": "0" }, { "last_affected": "c5cbbec54fe71c4de2d34f8c0ec8fbfdd7f17339" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" }, { "events": [ { "introduced": "4.4.5" }, { "fixed": "4.5" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" } ] }, { "package": { "ecosystem": "Linux", "name": "Kernel" }, "ranges": [ { "events": [ { "introduced": "4.5.0" }, { "fixed": "5.10.261" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.11.0" }, { "fixed": "6.1.178" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.2.0" }, { "fixed": "6.6.145" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.7.0" }, { "fixed": "6.12.96" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.13.0" }, { "fixed": "6.18.39" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.19.0" }, { "fixed": "7.1.4" } ], "type": "ECOSYSTEM" } ] } ], "database_specific": { "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64378.json" }, "details": "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(\u0026isw_nr_in_flight)\n inode_prepare_wbs_switch\n -\u003e passes SB_ACTIVE check\n __iget(inode)\n generic_shutdown_super\n sb-\u003es_flags \u0026= ~SB_ACTIVE\n cgroup_writeback_umount(sb)\n smp_mb()\n atomic_read(\u0026isw_nr_in_flight)\n rcu_barrier()\n -\u003e no pending RCU callbacks\n flush_workqueue(isw_wq)\n -\u003e nothing queued, returns\n evict_inodes(sb)\n -\u003e Inode skipped as isw still holds a ref.\n sop-\u003eput_super(sb)\n /* destroys percpu counters */\n -\u003e 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() -\u003e 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-\u003elist_lock when switching inodes\")) and is removed in a follow-up\npatch.", "id": "CVE-2026-64378", "modified": "2026-07-27T03:56:21.393041054Z", "published": "2026-07-25T08:50:29.006Z", "references": [ { "type": "WEB", "url": "https://git.kernel.org/stable/c/087d5b8b501c570f84bf655164e6698c3ce146e0" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/3c9c9648f77e4d14e50676bc51c2174ba9c8d361" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/53eeaf4d63068dbc7708b0c7adb20151c812feca" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/5c3265f3252b2ee50707adaaa3f9bd0df3df72de" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/685fc15a410885b6d4dee64de0dce721b9428b12" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/c923cc3cb5cd8945ceaf08252754110643446593" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/cba38ec4cbd3a7b8b942a8d52531a05be8a9ff0d" }, { "type": "ADVISORY", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64378.json" }, { "type": "ADVISORY", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64378" }, { "type": "PACKAGE", "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git" } ], "schema_version": "1.8.0", "summary": "writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()" }