CVE-2022-50552

In the Linux kernel, the following vulnerability has been resolved:

blk-mq: use quiesced elevator switch when reinitializing queues

The hctxs run_work may be racing with the elevator switch when reinitializing hardware queues. The queue is merely frozen in this context, but that only prevents requests from allocating and doesnt stop the hctx work from running. The work may get an elevator pointer thats being torn down, and can result in use-after-free errors and kernel panics (example below). Use the quiesced elevator switch instead, and make the previous one static since it is now only used locally.

nvme nvme0: resetting controller nvme nvme0: 32/0/0 default/read/poll queues BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 80000020c8861067 P4D 80000020c8861067 PUD 250f8c8067 PMD 0 Oops: 0000 [#1] SMP PTI Workqueue: kblockd blk_mq_run_work_fn RIP: 0010:kyber_has_work+0x29/0x70

…

Call Trace: __blk_mq_do_dispatch_sched+0x83/0x2b0 __blk_mq_sched_dispatch_requests+0x12e/0x170 blk_mq_sched_dispatch_requests+0x30/0x60 __blk_mq_run_hw_queue+0x2b/0x50 process_one_work+0x1ef/0x380 worker_thread+0x2d/0x3e0

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/63a681bcc32a43528ce0f690569f7f48e59c3963
• https://git.kernel.org/stable/c/8237c01f1696bc53c470493bf1fe092a107648a6
• https://git.kernel.org/stable/c/c478b3b2900f1834cf9eda5bfef0d5696099505d