Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: ext4: fix use-after-free in update_super_work when racing with umount Commit b98535d09179 ("ext4: fix bug_on in start_this_handle during umount filesystem") moved ext4_unregister_sysfs() before flushing s_sb_upd_work to prevent new error work from being queued via /proc/fs/ext4/xx/mb_groups reads during unmount. However, this introduced a use-after-free because update_super_work calls ext4_notify_error_sysfs() -> sysfs_notify() which accesses the kobject's kernfs_node after it has been freed by kobject_del() in ext4_unregister_sysfs(): update_super_work ext4_put_super ----------------- -------------- ext4_unregister_sysfs(sb) kobject_del(&sbi->s_kobj) __kobject_del() sysfs_remove_dir() kobj->sd = NULL sysfs_put(sd) kernfs_put() // RCU free ext4_notify_error_sysfs(sbi) sysfs_notify(&sbi->s_kobj) kn = kobj->sd // stale pointer kernfs_get(kn) // UAF on freed kernfs_node ext4_journal_destroy() flush_work(&sbi->s_sb_upd_work) Instead of reordering the teardown sequence, fix this by making ext4_notify_error_sysfs() detect that sysfs has already been torn down by checking s_kobj.state_in_sysfs, and skipping the sysfs_notify() call in that case. A dedicated mutex (s_error_notify_mutex) serializes ext4_notify_error_sysfs() against kobject_del() in ext4_unregister_sysfs() to prevent TOCTOU races where the kobject could be deleted between the state_in_sysfs check and the sysfs_notify() call.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 52c3a04f9ec2a16a4204d6274db338cb8d5b2d74 before c8fe17a1b308c3d8c703ebfb049b325f844342c3; affected b98535d091795a79336f520b0708457aacf55c67 before c4d829737329f2290dd41e290b7d75effdb2a7ff; affected b98535d091795a79336f520b0708457aacf55c67 before 9449f99ba04f5dd1c8423ad8a90b3651d7240d1d; affected b98535d091795a79336f520b0708457aacf55c67 before 034053378dd81837fd6c7a43b37ee2e58d4f0b4e; affected b98535d091795a79336f520b0708457aacf55c67 before c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe; affected b98535d091795a79336f520b0708457aacf55c67 before 08b10e6f37fc533a759e9833af0692242e8b3f93; affected b98535d091795a79336f520b0708457aacf55c67 before d15e4b0a418537aafa56b2cb80d44add83e83697; affected 585ef03c9e79672781f954daae730dfe24bf3a46; affected afe490e48d47df1b3f64012835c1bc2f075a8c8b; affected 5.15.38 before 5.15.203; affected 5.10.114 before 5.11; affected 5.17.6 before 5.18 |
| Linux / Linux | affected 5.18; unaffected 0 before 5.18; unaffected 5.15.203 through 5.15.*; unaffected 6.1.168 through 6.1.*; unaffected 6.6.131 through 6.6.*; unaffected 6.12.80 through 6.12.*; unaffected 6.18.21 through 6.18.*; unaffected 6.19.11 through 6.19.*; unaffected 7.0 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/c8fe17a1b308c3d8c703ebfb049b325f844342c3
- https://git.kernel.org/stable/c/c4d829737329f2290dd41e290b7d75effdb2a7ff
- https://git.kernel.org/stable/c/9449f99ba04f5dd1c8423ad8a90b3651d7240d1d
- https://git.kernel.org/stable/c/034053378dd81837fd6c7a43b37ee2e58d4f0b4e
- https://git.kernel.org/stable/c/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe
- https://git.kernel.org/stable/c/08b10e6f37fc533a759e9833af0692242e8b3f93
- https://git.kernel.org/stable/c/d15e4b0a418537aafa56b2cb80d44add83e83697
ADP enrichment
No English description supplied.
No English description supplied.
No references supplied.