scsi: ufs: core: Fix ufshcd_clear_cmd racing issue

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

scsi: ufs: core: Fix ufshcd_clear_cmd racing issue

When ufshcd_clear_cmd is racing with the completion ISR, the completed tag

of the request's mq_hctx pointer will be set to NULL by the ISR. And

ufshcd_clear_cmd's call to ufshcd_mcq_req_to_hwq will get NULL pointer KE.

Return success when the request is completed by ISR because sq does not

need cleanup.

The racing flow is:

Thread A

ufshcd_err_handler step 1

ufshcd_try_to_abort_task

ufshcd_cmd_inflight(true) step 3

ufshcd_clear_cmd

...

ufshcd_mcq_req_to_hwq

blk_mq_unique_tag

rq->mq_hctx->queue_num step 5

Thread B

ufs_mtk_mcq_intr(cq complete ISR) step 2

scsi_done

...

__blk_mq_free_request

rq->mq_hctx = NULL; step 4

Below is KE back trace:

ufshcd_try_to_abort_task: cmd pending in the device. tag = 6

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000194

pc : [0xffffffd589679bf8] blk_mq_unique_tag+0x8/0x14

lr : [0xffffffd5862f95b4] ufshcd_mcq_sq_cleanup+0x6c/0x1cc [ufs_mediatek_mod_ise]

Workqueue: ufs_eh_wq_0 ufshcd_err_handler [ufs_mediatek_mod_ise]

Call trace:

dump_backtrace+0xf8/0x148

show_stack+0x18/0x24

dump_stack_lvl+0x60/0x7c

dump_stack+0x18/0x3c

mrdump_common_die+0x24c/0x398 [mrdump]

ipanic_die+0x20/0x34 [mrdump]

notify_die+0x80/0xd8

die+0x94/0x2b8

__do_kernel_fault+0x264/0x298

do_page_fault+0xa4/0x4b8

do_translation_fault+0x38/0x54

do_mem_abort+0x58/0x118

el1_abort+0x3c/0x5c

el1h_64_sync_handler+0x54/0x90

el1h_64_sync+0x68/0x6c

blk_mq_unique_tag+0x8/0x14

ufshcd_clear_cmd+0x34/0x118 [ufs_mediatek_mod_ise]

ufshcd_try_to_abort_task+0x2c8/0x5b4 [ufs_mediatek_mod_ise]

ufshcd_err_handler+0xa7c/0xfa8 [ufs_mediatek_mod_ise]

process_one_work+0x208/0x4fc

worker_thread+0x228/0x438

kthread+0x104/0x1d4

ret_from_fork+0x10/0x20