Re: [PATCH v3] scsi: ufs: core: fix racing issue during ufshcd_mcq_abort

[Dan Carpenter <dan.carpenter@linaro.org>]

Hi SEO,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/SEO-HOYOUNG/scsi-ufs-core-fix-racing-issue-during-ufshcd_mcq_abort/20231121-151923
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git for-next
patch link:    https://lore.kernel.org/r/20231121071128.7743-1-hy50.seo%40samsung.com
patch subject: [PATCH v3] scsi: ufs: core: fix racing issue during ufshcd_mcq_abort
config: powerpc-randconfig-r071-20231122 (https://download.01.org/0day-ci/archive/20231122/202311220618.OnEhSic6-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 13.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231122/202311220618.OnEhSic6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202311220618.OnEhSic6-lkp@intel.com/

smatch warnings:
drivers/ufs/core/ufs-mcq.c:515 ufshcd_mcq_sq_cleanup() warn: variable dereferenced before check 'cmd' (see line 511)

vim +/cmd +515 drivers/ufs/core/ufs-mcq.c

8d7290348992f2 Bao D. Nguyen   2023-05-29  498  int ufshcd_mcq_sq_cleanup(struct ufs_hba *hba, int task_tag)
8d7290348992f2 Bao D. Nguyen   2023-05-29  499  {
8d7290348992f2 Bao D. Nguyen   2023-05-29  500  	struct ufshcd_lrb *lrbp = &hba->lrb[task_tag];
8d7290348992f2 Bao D. Nguyen   2023-05-29  501  	struct scsi_cmnd *cmd = lrbp->cmd;
8d7290348992f2 Bao D. Nguyen   2023-05-29  502  	struct ufs_hw_queue *hwq;
8d7290348992f2 Bao D. Nguyen   2023-05-29  503  	void __iomem *reg, *opr_sqd_base;
8d7290348992f2 Bao D. Nguyen   2023-05-29  504  	u32 nexus, id, val;
8d7290348992f2 Bao D. Nguyen   2023-05-29  505  	int err;
8d7290348992f2 Bao D. Nguyen   2023-05-29  506  
aa9d5d0015a8b7 Po-Wen Kao      2023-06-12  507  	if (hba->quirks & UFSHCD_QUIRK_MCQ_BROKEN_RTC)
aa9d5d0015a8b7 Po-Wen Kao      2023-06-12  508  		return -ETIMEDOUT;
aa9d5d0015a8b7 Po-Wen Kao      2023-06-12  509  
5363c9d813101c SEO HOYOUNG     2023-11-21  510  	if (!ufshcd_cmd_inflight(cmd) ||
5363c9d813101c SEO HOYOUNG     2023-11-21 @511  	    test_bit(SCMD_STATE_COMPLETE, &cmd->state))
                                                                                          ^^^^^^^^^^^
The patch adds a new unchecked dereference

5363c9d813101c SEO HOYOUNG     2023-11-21  512  		return 0;
5363c9d813101c SEO HOYOUNG     2023-11-21  513  
8d7290348992f2 Bao D. Nguyen   2023-05-29  514  	if (task_tag != hba->nutrs - UFSHCD_NUM_RESERVED) {
8d7290348992f2 Bao D. Nguyen   2023-05-29 @515  		if (!cmd)
                                                                     ^^^
But the old code assumed "cmd" could be NULL

8d7290348992f2 Bao D. Nguyen   2023-05-29  516  			return -EINVAL;
8d7290348992f2 Bao D. Nguyen   2023-05-29  517  		hwq = ufshcd_mcq_req_to_hwq(hba, scsi_cmd_to_rq(cmd));
8d7290348992f2 Bao D. Nguyen   2023-05-29  518  	} else {
8d7290348992f2 Bao D. Nguyen   2023-05-29  519  		hwq = hba->dev_cmd_queue;
8d7290348992f2 Bao D. Nguyen   2023-05-29  520  	}

-- 
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