CVE-2026-99254
In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task w…
Impact
In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. task_work_run() only returns when it finds the list empty. If the rings are released from inside the cancellation, because requests of other rings held the last references to their files, up to 64 work items keep sending callbacks to the one task which is running them. It never finds the list empty, never gets back to the cancellation, the nodes stay, and so it goes on: a task with 60 pairs of rings which poll each other ran 280000 callbacks in 5 seconds, 20 seconds after exit_group(). It ends when all the senders happen to be late at the same time. Until then the task keeps a CPU and the work items busy. An exiting task can't be killed meanwhile. execve() cancels the requests in the same way, so a live task can get stuck there as well, for minutes. If it takes more than five, the work items run into the WARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No privilege is needed for any of this. If the callback has met a task in cancellation, wait a little before it is sent again. Nobody has to wake the work item up for that: either the node is gone by then, or it is the turn of the next round.
Affected products · Linux
| Product | Affected versions |
|---|---|
| Linux | from d56d938b4bef3e1421a42023cdcd6e13c1f50831 before a22fb44e988b01b82235ea07f0bf0fc73e256596 from d56d938b4bef3e1421a42023cdcd6e13c1f50831 before 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1 from d56d938b4bef3e1421a42023cdcd6e13c1f50831 before 61c761fc21e00e45c33c2bb596be442d92fb8792 from d56d938b4bef3e1421a42023cdcd6e13c1f50831 before 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9 from d56d938b4bef3e1421a42023cdcd6e13c1f50831 before abdc57c7ebabaaf0b622178a6a85834e1e54ff80 Version 5.12 |
References
- NVD record
- CVE.org record
- GitHub advisory
- https://git.kernel.org/stable/c/a22fb44e988b01b82235ea07f0bf0fc73e256596
- https://git.kernel.org/stable/c/2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1
- https://git.kernel.org/stable/c/61c761fc21e00e45c33c2bb596be442d92fb8792
- https://git.kernel.org/stable/c/14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9
- https://git.kernel.org/stable/c/abdc57c7ebabaaf0b622178a6a85834e1e54ff80
- https://github.com/advisories/GHSA-g7fp-pvxq-ggj5
- https://nvd.nist.gov/vuln/detail/CVE-2026-99254
- https://git.kernel.org/stable/c/22e643e61b9b6299b42ff7d88bab48bccada8a5d
- https://git.kernel.org/stable/c/f334e79a11e084713e82402b1a7a0e321526992a