[PATCH 5.10 0/2] scsi: ufs: core: Fix task management completion

[PATCH 5.10 0/2] scsi: ufs: core: Fix task management completion

[Adrian Hunter]

Hi

Here are 2 patches backported for v5.10.  Upstream there is a third patch
associated with these i.e. commit 5cb37a26355 ("scsi: ufs: core: Fix
another task management completion race"), but it is not needed because
v5.10 has different lock usage.


Adrian Hunter (2):
      scsi: ufs: core: Fix task management completion
      scsi: ufs: core: Fix task management completion timeout race

 drivers/scsi/ufs/ufshcd.c | 57 +++++++++++++++++++----------------------------
 drivers/scsi/ufs/ufshcd.h |  1 +
 2 files changed, 24 insertions(+), 34 deletions(-)


Regards
Adrian

[PATCH 5.10 1/2] scsi: ufs: core: Fix task management completion

[Adrian Hunter]

commit f5ef336fd2e4c36dedae4e7ca66cf5349d6fda62 upstream.

The UFS driver uses blk_mq_tagset_busy_iter() when identifying task
management requests to complete, however blk_mq_tagset_busy_iter() doesn't
work.

blk_mq_tagset_busy_iter() only iterates requests dispatched by the block
layer. That appears as if it might have started since commit 37f4a24c2469
("blk-mq: centralise related handling into blk_mq_get_driver_tag") which
removed 'data->hctx->tags->rqs[rq->tag] = rq' from blk_mq_rq_ctx_init()
which gets called:

	blk_get_request
		blk_mq_alloc_request
			__blk_mq_alloc_request
				blk_mq_rq_ctx_init

Since UFS task management requests are not dispatched by the block layer,
hctx->tags->rqs[rq->tag] remains NULL, and since blk_mq_tagset_busy_iter()
relies on finding requests using hctx->tags->rqs[rq->tag], UFS task
management requests are never found by blk_mq_tagset_busy_iter().

By using blk_mq_tagset_busy_iter(), the UFS driver was relying on internal
details of the block layer, which was fragile and subsequently got
broken. Fix by removing the use of blk_mq_tagset_busy_iter() and having the
driver keep track of task management requests.

Link: https://lore.kernel.org/r/20210922091059.4040-1-adrian.hunter@intel.com
Fixes: 1235fc569e0b ("scsi: ufs: core: Fix task management request completion timeout")
Fixes: 69a6c269c097 ("scsi: ufs: Use blk_{get,put}_request() to allocate and free TMFs")
Cc: stable@vger.kernel.org
Tested-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[Adrian: Backport to v5.10]
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 drivers/scsi/ufs/ufshcd.c | 52 +++++++++++++++++----------------------
 drivers/scsi/ufs/ufshcd.h |  1 +
 2 files changed, 24 insertions(+), 29 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 930f35863cbb..5fd0a6ed181c 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6099,27 +6099,6 @@ static irqreturn_t ufshcd_check_errors(struct ufs_hba *hba)
 	return retval;
 }
 
-struct ctm_info {
-	struct ufs_hba	*hba;
-	unsigned long	pending;
-	unsigned int	ncpl;
-};
-
-static bool ufshcd_compl_tm(struct request *req, void *priv, bool reserved)
-{
-	struct ctm_info *const ci = priv;
-	struct completion *c;
-
-	WARN_ON_ONCE(reserved);
-	if (test_bit(req->tag, &ci->pending))
-		return true;
-	ci->ncpl++;
-	c = req->end_io_data;
-	if (c)
-		complete(c);
-	return true;
-}
-
 /**
  * ufshcd_tmc_handler - handle task management function completion
  * @hba: per adapter instance
@@ -6130,14 +6109,22 @@ static bool ufshcd_compl_tm(struct request *req, void *priv, bool reserved)
  */
 static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba)
 {
-	struct request_queue *q = hba->tmf_queue;
-	struct ctm_info ci = {
-		.hba	 = hba,
-		.pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL),
-	};
+	unsigned long pending, issued;
+	irqreturn_t ret = IRQ_NONE;
+	int tag;
+
+	pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
+
+	issued = hba->outstanding_tasks & ~pending;
+	for_each_set_bit(tag, &issued, hba->nutmrs) {
+		struct request *req = hba->tmf_rqs[tag];
+		struct completion *c = req->end_io_data;
+
+		complete(c);
+		ret = IRQ_HANDLED;
+	}
 
-	blk_mq_tagset_busy_iter(q->tag_set, ufshcd_compl_tm, &ci);
-	return ci.ncpl ? IRQ_HANDLED : IRQ_NONE;
+	return ret;
 }
 
 /**
@@ -6267,9 +6254,9 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
 	ufshcd_hold(hba, false);
 
 	spin_lock_irqsave(host->host_lock, flags);
-	blk_mq_start_request(req);
 
 	task_tag = req->tag;
+	hba->tmf_rqs[req->tag] = req;
 	treq->req_header.dword_0 |= cpu_to_be32(task_tag);
 
 	memcpy(hba->utmrdl_base_addr + task_tag, treq, sizeof(*treq));
@@ -6313,6 +6300,7 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
 	}
 
 	spin_lock_irqsave(hba->host->host_lock, flags);
+	hba->tmf_rqs[req->tag] = NULL;
 	__clear_bit(task_tag, &hba->outstanding_tasks);
 	spin_unlock_irqrestore(hba->host->host_lock, flags);
 
@@ -9235,6 +9223,12 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 		err = PTR_ERR(hba->tmf_queue);
 		goto free_tmf_tag_set;
 	}
+	hba->tmf_rqs = devm_kcalloc(hba->dev, hba->nutmrs,
+				    sizeof(*hba->tmf_rqs), GFP_KERNEL);
+	if (!hba->tmf_rqs) {
+		err = -ENOMEM;
+		goto free_tmf_queue;
+	}
 
 	/* Reset the attached device */
 	ufshcd_vops_device_reset(hba);
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 1ba9c786feb6..35dd5197ccb9 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -734,6 +734,7 @@ struct ufs_hba {
 
 	struct blk_mq_tag_set tmf_tag_set;
 	struct request_queue *tmf_queue;
+	struct request **tmf_rqs;
 
 	struct uic_command *active_uic_cmd;
 	struct mutex uic_cmd_mutex;
-- 
2.25.1

[PATCH 5.10 2/2] scsi: ufs: core: Fix task management completion timeout race

[Adrian Hunter]

commit 886fe2915cce6658b0fc19e64b82879325de61ea upstream.

__ufshcd_issue_tm_cmd() clears req->end_io_data after timing out, which
races with the completion function ufshcd_tmc_handler() which expects
req->end_io_data to have a value.

Note __ufshcd_issue_tm_cmd() and ufshcd_tmc_handler() are already
synchronized using hba->tmf_rqs and hba->outstanding_tasks under the
host_lock spinlock.

It is also not necessary (nor typical) to clear req->end_io_data because
the block layer does it before allocating out requests e.g. via
blk_get_request().

So fix by not clearing it.

Link: https://lore.kernel.org/r/20211108064815.569494-2-adrian.hunter@intel.com
Fixes: f5ef336fd2e4 ("scsi: ufs: core: Fix task management completion")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[Adrian: Backport to v5.10]
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 drivers/scsi/ufs/ufshcd.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 5fd0a6ed181c..e3a9a02cadf5 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6280,11 +6280,6 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
 	err = wait_for_completion_io_timeout(&wait,
 			msecs_to_jiffies(TM_CMD_TIMEOUT));
 	if (!err) {
-		/*
-		 * Make sure that ufshcd_compl_tm() does not trigger a
-		 * use-after-free.
-		 */
-		req->end_io_data = NULL;
 		ufshcd_add_tm_upiu_trace(hba, task_tag, "tm_complete_err");
 		dev_err(hba->dev, "%s: task management cmd 0x%.2x timed-out\n",
 				__func__, tm_function);
-- 
2.25.1

Re: [PATCH 5.10 0/2] scsi: ufs: core: Fix task management completion

[Greg KH]

On Tue, Nov 23, 2021 at 02:19:28PM +0200, Adrian Hunter wrote:
> Hi
> 
> Here are 2 patches backported for v5.10.  Upstream there is a third patch
> associated with these i.e. commit 5cb37a26355 ("scsi: ufs: core: Fix
> another task management completion race"), but it is not needed because
> v5.10 has different lock usage.
> 
> 
> Adrian Hunter (2):
>       scsi: ufs: core: Fix task management completion
>       scsi: ufs: core: Fix task management completion timeout race
> 
>  drivers/scsi/ufs/ufshcd.c | 57 +++++++++++++++++++----------------------------
>  drivers/scsi/ufs/ufshcd.h |  1 +
>  2 files changed, 24 insertions(+), 34 deletions(-)
> 

Both now queued up, thanks.

greg k-h