Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: writeback: Fix use after free in inode_switch_wbs_work_fn() inode_switch_wbs_work_fn() has a loop like: wb_get(new_wb); while (1) { list = llist_del_all(&new_wb->switch_wbs_ctxs); /* Nothing to do? */ if (!list) break; ... process the items ... } Now adding of items to the list looks like: wb_queue_isw() if (llist_add(&isw->list, &wb->switch_wbs_ctxs)) queue_work(isw_wq, &wb->switch_work); Because inode_switch_wbs_work_fn() loops when processing isw items, it can happen that wb->switch_work is pending while wb->switch_wbs_ctxs is empty. This is a problem because in that case wb can get freed (no isw items -> no wb reference) while the work is still pending causing use-after-free issues. We cannot just fix this by cancelling work when freeing wb because that could still trigger problematic 0 -> 1 transitions on wb refcount due to wb_get() in inode_switch_wbs_work_fn(). It could be all handled with more careful code but that seems unnecessarily complex so let's avoid that until it is proven that the looping actually brings practical benefit. Just remove the loop from inode_switch_wbs_work_fn() instead. That way when wb_queue_isw() queues work, we are guaranteed we have added the first item to wb->switch_wbs_ctxs and nobody is going to remove it (and drop the wb reference it holds) until the queued work runs.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected d072b38a64ddbc2d58c2e525a24af24ecbfebcb7 before 382cf81cae89e58d22b4bdc38891cd4d0b9ba921; affected ac7b2c21f2269d815ad0cdf0f8258d55185b805c before 19ec404b079be057b387643ba0c69bbcc5867c35; affected fabfc1fcddc5d8185722d4fde5f0968c4760b71e before 156cc63691c1f20905510b1007896e090355e6c2; affected e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b before 028103656b84273c73e9e271cf95c9f3421f4b8a; affected e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b before 9223e5f30403a9b506d6d0bff4f2e29a2d7d46af; affected e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b before 6689f01d6740cf358932b3e97ee968c6099800d9 |
| Linux / Linux | affected 6.18; unaffected 0 before 6.18; unaffected 6.18.25 through 6.18.*; unaffected 7.0.2 through 7.0.*; unaffected 7.1 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/382cf81cae89e58d22b4bdc38891cd4d0b9ba921
- https://git.kernel.org/stable/c/19ec404b079be057b387643ba0c69bbcc5867c35
- https://git.kernel.org/stable/c/156cc63691c1f20905510b1007896e090355e6c2
- https://git.kernel.org/stable/c/028103656b84273c73e9e271cf95c9f3421f4b8a
- https://git.kernel.org/stable/c/9223e5f30403a9b506d6d0bff4f2e29a2d7d46af
- https://git.kernel.org/stable/c/6689f01d6740cf358932b3e97ee968c6099800d9
ADP enrichment
A flaw was found in the Linux kernel. A use-after-free vulnerability exists in the `inode_switch_wbs_work_fn()` function, part of the kernel's writeback subsystem. This issue arises when a work item remains active after its associated memory object (`wb`) has been released, leading to system instability. An attacker could potentially exploit this vulnerability to cause a denial of service.