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CVE PROGRAM SOURCE RECORD7.8 High

CVE-2026-31703

writeback: Fix use after free in inode_switch_wbs_work_fn()

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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 products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • d072b38a64ddbc2d58c2e525a24af24ecbfebcb7 to < 382cf81cae89e58d22b4bdc38891cd4d0b9ba921affected
  • ac7b2c21f2269d815ad0cdf0f8258d55185b805c to < 19ec404b079be057b387643ba0c69bbcc5867c35affected
  • fabfc1fcddc5d8185722d4fde5f0968c4760b71e to < 156cc63691c1f20905510b1007896e090355e6c2affected
  • e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b to < 028103656b84273c73e9e271cf95c9f3421f4b8aaffected
  • e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b to < 9223e5f30403a9b506d6d0bff4f2e29a2d7d46afaffected
  • e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b to < 6689f01d6740cf358932b3e97ee968c6099800d9affected

Linux Linux

Default version status: affected

  • 6.18affected
  • 0 to < 6.18unaffected
  • 6.18.25 to ≤ 6.18.*unaffected
  • 7.0.2 to ≤ 7.0.*unaffected
  • 7.1 to ≤ *unaffected

References