CVE-2021-46942

io_uring: fix shared sqpoll cancellation hangs

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring: fix shared sqpoll cancellation hangs [ 736.982891] INFO: task iou-sqp-4294:4295 blocked for more than 122 seconds. [ 736.982897] Call Trace: [ 736.982901] schedule+0x68/0xe0 [ 736.982903] io_uring_cancel_sqpoll+0xdb/0x110 [ 736.982908] io_sqpoll_cancel_cb+0x24/0x30 [ 736.982911] io_run_task_work_head+0x28/0x50 [ 736.982913] io_sq_thread+0x4e3/0x720 We call io_uring_cancel_sqpoll() one by one for each ctx either in sq_thread() itself or via task works, and it's intended to cancel all requests of a specified context. However the function uses per-task counters to track the number of inflight requests, so it counts more requests than available via currect io_uring ctx and goes to sleep for them to appear (e.g. from IRQ), that will never happen. Cancel a bit more than before, i.e. all ctxs that share sqpoll and continue to use shared counters. Don't forget that we should not remove ctx from the list before running that task_work sqpoll-cancel, otherwise the function wouldn't be able to find the context and will hang.

5.5

CVSS

Severity: Medium

CVSS 3.1 •

EPSS 0.03%

Affected: Linux Linux

References

Link	Tags
https://git.kernel.org/stable/c/cb5e0b3d0f993a6268c1a2c7ede2f9aa0c17ef68	patch
https://git.kernel.org/stable/c/734551df6f9bedfbefcd113ede665945e9de0b99	patch

Frequently Asked Questions

What is the severity of CVE-2021-46942?: CVE-2021-46942 has been scored as a medium severity vulnerability.
How to fix CVE-2021-46942?: To fix CVE-2021-46942, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2021-46942 being actively exploited in the wild?: As for now, there are no information to confirm that CVE-2021-46942 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-46942?: CVE-2021-46942 affects Linux Linux, Linux Linux.

This platform uses data from the NIST NVD, MITRE CVE, MITRE CWE, First.org and CISA KEV but is not endorsed or certified by these entities. CVE is a registred trademark of the MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. CWE is a registred trademark of the MITRE Corporation and the authoritative source of CWE content is MITRE's CWE web site.