[PATCH v2] scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()

[PATCH v2] scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()

[Chenyuan Yang]

A race can occur between the MCQ completion path and the abort handler:
once a request completes, __blk_mq_free_request() sets rq->mq_hctx to
NULL, meaning the subsequent ufshcd_mcq_req_to_hwq() call in
ufshcd_mcq_abort() can return a NULL pointer. If this NULL pointer is
dereferenced, the kernel will crash.

Add a NULL check for the returned hwq pointer. If hwq is NULL, log an
error and return FAILED, preventing a potential NULL-pointer dereference.
As suggested by Bart, the ufshcd_cmd_inflight() check is removed.

This is similar to the fix in commit 74736103fb41
("scsi: ufs: core: Fix ufshcd_abort_one racing issue").

This is found by our static analysis tool KNighter.

Signed-off-by: Chenyuan Yang <chenyuan0y@gmail.com>
Fixes: f1304d442077 ("scsi: ufs: mcq: Added ufshcd_mcq_abort()")
---
 drivers/ufs/core/ufs-mcq.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
index 240ce135bbfb..f1294c29f484 100644
--- a/drivers/ufs/core/ufs-mcq.c
+++ b/drivers/ufs/core/ufs-mcq.c
@@ -677,13 +677,6 @@ int ufshcd_mcq_abort(struct scsi_cmnd *cmd)
 	unsigned long flags;
 	int err;
 
-	if (!ufshcd_cmd_inflight(lrbp->cmd)) {
-		dev_err(hba->dev,
-			"%s: skip abort. cmd at tag %d already completed.\n",
-			__func__, tag);
-		return FAILED;
-	}
-
 	/* Skip task abort in case previous aborts failed and report failure */
 	if (lrbp->req_abort_skip) {
 		dev_err(hba->dev, "%s: skip abort. tag %d failed earlier\n",
@@ -692,6 +685,11 @@ int ufshcd_mcq_abort(struct scsi_cmnd *cmd)
 	}
 
 	hwq = ufshcd_mcq_req_to_hwq(hba, scsi_cmd_to_rq(cmd));
+	if (!hwq) {
+		dev_err(hba->dev, "%s: skip abort. cmd at tag %d already completed.\n",
+			__func__, tag);
+		return FAILED;
+	}
 
 	if (ufshcd_mcq_sqe_search(hba, hwq, tag)) {
 		/*
-- 
2.34.1

Re: [PATCH v2] scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()

[Bart Van Assche]

On 4/9/25 5:13 PM, Chenyuan Yang wrote:
> A race can occur between the MCQ completion path and the abort handler:
> once a request completes, __blk_mq_free_request() sets rq->mq_hctx to
> NULL, meaning the subsequent ufshcd_mcq_req_to_hwq() call in
> ufshcd_mcq_abort() can return a NULL pointer. If this NULL pointer is
> dereferenced, the kernel will crash.
> 
> Add a NULL check for the returned hwq pointer. If hwq is NULL, log an
> error and return FAILED, preventing a potential NULL-pointer dereference.
> As suggested by Bart, the ufshcd_cmd_inflight() check is removed.
> 
> This is similar to the fix in commit 74736103fb41
> ("scsi: ufs: core: Fix ufshcd_abort_one racing issue").
> 
> This is found by our static analysis tool KNighter.
Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH v2] scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()

[Peter Wang (王信友)]

On Wed, 2025-04-09 at 19:13 -0500, Chenyuan Yang wrote:
> 
> A race can occur between the MCQ completion path and the abort
> handler:
> once a request completes, __blk_mq_free_request() sets rq->mq_hctx to
> NULL, meaning the subsequent ufshcd_mcq_req_to_hwq() call in
> ufshcd_mcq_abort() can return a NULL pointer. If this NULL pointer is
> dereferenced, the kernel will crash.
> 
> Add a NULL check for the returned hwq pointer. If hwq is NULL, log an
> error and return FAILED, preventing a potential NULL-pointer
> dereference.
> As suggested by Bart, the ufshcd_cmd_inflight() check is removed.
> 
> This is similar to the fix in commit 74736103fb41
> ("scsi: ufs: core: Fix ufshcd_abort_one racing issue").
> 
> This is found by our static analysis tool KNighter.
> 
> Signed-off-by: Chenyuan Yang <chenyuan0y@gmail.com>
> Fixes: f1304d442077 ("scsi: ufs: mcq: Added ufshcd_mcq_abort()")
> ---
>  drivers/ufs/core/ufs-mcq.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
> index 240ce135bbfb..f1294c29f484 100644
> --- a/drivers/ufs/core/ufs-mcq.c
> +++ b/drivers/ufs/core/ufs-mcq.c
> @@ -677,13 +677,6 @@ int ufshcd_mcq_abort(struct scsi_cmnd *cmd)
>         unsigned long flags;
>         int err;
> 
> -       if (!ufshcd_cmd_inflight(lrbp->cmd)) {
> -               dev_err(hba->dev,
> -                       "%s: skip abort. cmd at tag %d already
> completed.\n",
> -                       __func__, tag);
> -               return FAILED;
> -       }
> -
>         /* Skip task abort in case previous aborts failed and report
> failure */
>         if (lrbp->req_abort_skip) {
>                 dev_err(hba->dev, "%s: skip abort. tag %d failed
> earlier\n",
> @@ -692,6 +685,11 @@ int ufshcd_mcq_abort(struct scsi_cmnd *cmd)
>         }
> 
>         hwq = ufshcd_mcq_req_to_hwq(hba, scsi_cmd_to_rq(cmd));
> +       if (!hwq) {
> +               dev_err(hba->dev, "%s: skip abort. cmd at tag %d
> already completed.\n",
> +                       __func__, tag);
> +               return FAILED;
> +       }
> 
>         if (ufshcd_mcq_sqe_search(hba, hwq, tag)) {
>                 /*
> --
> 2.34.1
> 

Reviewed-by: Peter Wang <peter.wang@mediatek.com>

Re: [PATCH v2] scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()

[Martin K. Petersen]

On Wed, 09 Apr 2025 19:13:20 -0500, Chenyuan Yang wrote:

> A race can occur between the MCQ completion path and the abort handler:
> once a request completes, __blk_mq_free_request() sets rq->mq_hctx to
> NULL, meaning the subsequent ufshcd_mcq_req_to_hwq() call in
> ufshcd_mcq_abort() can return a NULL pointer. If this NULL pointer is
> dereferenced, the kernel will crash.
> 
> Add a NULL check for the returned hwq pointer. If hwq is NULL, log an
> error and return FAILED, preventing a potential NULL-pointer dereference.
> As suggested by Bart, the ufshcd_cmd_inflight() check is removed.
> 
> [...]

Applied to 6.15/scsi-fixes, thanks!

[1/1] scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()
      https://git.kernel.org/mkp/scsi/c/4c3240850629

-- 
Martin K. Petersen	Oracle Linux Engineering