[PATCH 0/2] s390/dasd: fix buffer alignment validation

[PATCH 0/2] s390/dasd: fix buffer alignment validation

[Stefan Haberland]

Hi Jens,

please apply the following two patches that fix buffer alignment
handling in the DASD driver.
The first patch corrects the error mapping for misaligned requests,
and the second enforces proper alignment validation in the block layer.


Jaehoon Kim (2):
  s390/dasd: Return BLK_STS_INVAL for EINVAL from do_dasd_request
  s390/dasd: enforce dma_alignment to ensure proper buffer validation

 drivers/s390/block/dasd.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

-- 
2.48.1

[PATCH 1/2] s390/dasd: Return BLK_STS_INVAL for EINVAL from do_dasd_request

[Stefan Haberland]

From: Jaehoon Kim <jhkim@linux.ibm.com>

Currently, if CCW request creation fails with -EINVAL, the DASD driver
returns BLK_STS_IOERR to the block layer.

This can happen, for example, when a user-space application such as QEMU
passes a misaligned buffer, but the original cause of the error is
masked as a generic I/O error.

This patch changes the behavior so that -EINVAL is returned as
BLK_STS_INVAL, allowing user space to properly detect alignment issues
instead of interpreting them as I/O errors.

Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Cc: stable@vger.kernel.org #6.11+
Signed-off-by: Jaehoon Kim <jhkim@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 506a947d00a5..6224ba412623 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -3114,12 +3114,14 @@ static blk_status_t do_dasd_request(struct blk_mq_hw_ctx *hctx,
 		    PTR_ERR(cqr) == -ENOMEM ||
 		    PTR_ERR(cqr) == -EAGAIN) {
 			rc = BLK_STS_RESOURCE;
-			goto out;
+		} else if (PTR_ERR(cqr) == -EINVAL) {
+			rc = BLK_STS_INVAL;
+		} else {
+			DBF_DEV_EVENT(DBF_ERR, basedev,
+				      "CCW creation failed (rc=%ld) on request %p",
+				      PTR_ERR(cqr), req);
+			rc = BLK_STS_IOERR;
 		}
-		DBF_DEV_EVENT(DBF_ERR, basedev,
-			      "CCW creation failed (rc=%ld) on request %p",
-			      PTR_ERR(cqr), req);
-		rc = BLK_STS_IOERR;
 		goto out;
 	}
 	/*
-- 
2.48.1

[PATCH 2/2] s390/dasd: enforce dma_alignment to ensure proper buffer validation

[Stefan Haberland]

From: Jaehoon Kim <jhkim@linux.ibm.com>

The block layer validates buffer alignment using the device's
dma_alignment value. If dma_alignment is smaller than
logical_block_size(bp_block) -1, misaligned buffer incorrectly pass
validation and propagate to the lower-level driver.

This patch adjusts dma_alignment to be at least logical_block_size -1,
ensuring that misalignment buffers are properly rejected at the block
layer and do not reach the DASD driver unnecessarily.

Fixes: 2a07bb64d801 ("s390/dasd: Remove DMA alignment")
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Cc: stable@vger.kernel.org #6.11+
Signed-off-by: Jaehoon Kim <jhkim@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 6224ba412623..417a2dcf1587 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -334,6 +334,11 @@ static int dasd_state_basic_to_ready(struct dasd_device *device)
 	lim.max_dev_sectors = device->discipline->max_sectors(block);
 	lim.max_hw_sectors = lim.max_dev_sectors;
 	lim.logical_block_size = block->bp_block;
+	/*
+	 * Adjust dma_alignment to match block_size - 1
+	 * to ensure proper buffer alignment checks in the block layer.
+	 */
+	lim.dma_alignment = lim.logical_block_size - 1;
 
 	if (device->discipline->has_discard) {
 		unsigned int max_bytes;
-- 
2.48.1

Re: [PATCH 0/2] s390/dasd: fix buffer alignment validation

[Jens Axboe]

On Thu, 25 Sep 2025 17:47:06 +0200, Stefan Haberland wrote:
> please apply the following two patches that fix buffer alignment
> handling in the DASD driver.
> The first patch corrects the error mapping for misaligned requests,
> and the second enforces proper alignment validation in the block layer.
> 
> 
> Jaehoon Kim (2):
>   s390/dasd: Return BLK_STS_INVAL for EINVAL from do_dasd_request
>   s390/dasd: enforce dma_alignment to ensure proper buffer validation
> 
> [...]

Applied, thanks!

[1/2] s390/dasd: Return BLK_STS_INVAL for EINVAL from do_dasd_request
      (no commit info)
[2/2] s390/dasd: enforce dma_alignment to ensure proper buffer validation
      (no commit info)

Best regards,
-- 
Jens Axboe