CVE-2021-47622

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

scsi: ufs: Fix a deadlock in the error handler

The following deadlock has been observed on a test setup:

• All tags allocated

• The SCSI error handler calls ufshcd_eh_host_reset_handler()

• ufshcd_eh_host_reset_handler() queues work that calls ufshcd_err_handler()

• ufshcd_err_handler() locks up as follows:

Workqueue: ufs_eh_wq_0 ufshcd_err_handler.cfi_jt Call trace: __switch_to+0x298/0x5d8 __schedule+0x6cc/0xa94 schedule+0x12c/0x298 blk_mq_get_tag+0x210/0x480 __blk_mq_alloc_request+0x1c8/0x284 blk_get_request+0x74/0x134 ufshcd_exec_dev_cmd+0x68/0x640 ufshcd_verify_dev_init+0x68/0x35c ufshcd_probe_hba+0x12c/0x1cb8 ufshcd_host_reset_and_restore+0x88/0x254 ufshcd_reset_and_restore+0xd0/0x354 ufshcd_err_handler+0x408/0xc58 process_one_work+0x24c/0x66c worker_thread+0x3e8/0xa4c kthread+0x150/0x1b4 ret_from_fork+0x10/0x30

Fix this lockup by making ufshcd_exec_dev_cmd() allocate a reserved request.

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/493c9e850677df8b4eda150c2364b1c1a72ed724
• https://git.kernel.org/stable/c/945c3cca05d78351bba29fa65d93834cb7934c7b
• https://git.kernel.org/stable/c/d69d98d8edf90e25e4e09930dd36dd6d09dd6768