s390/dasd: enforce dma_alignment to ensure proper buffer validation

commit 130e6de upstream.

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: 2a07bb6 ("s390/dasd: Remove DMA alignment")
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Cc: stable@vger.kernel.org Rust-for-Linux#6.11+
Signed-off-by: Jaehoon Kim <jhkim@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Jaehoon Kim

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;