libata: set queue DMA alignment to sector size for ATAPI too

ata_pio_sectors() expects buffer for each sector to be contained in a
single page; otherwise, it ends up overrunning the first page.  This
is achieved by setting queue DMA alignment.  If sector_size is smaller
than PAGE_SIZE and all buffers are sector_size aligned, buffer for
each sector is always contained in a single page.

This wasn't applied to ATAPI devices but IDENTIFY_PACKET is executed
as ATA_PROT_PIO and thus uses ata_pio_sectors().  Newer versions of
udev issue IDENTIFY_PACKET with unaligned buffer triggering the
problem and causing oops.

This patch fixes the problem by setting sdev->sector_size to
ATA_SECT_SIZE on ATATPI devices and always setting DMA alignment to
sector_size.  While at it, add a warning for the unlikely but still
possible scenario where sector_size is larger than PAGE_SIZE, in which
case the alignment wouldn't be enough.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: John Stanley <jpsinthemix@verizon.net>
Tested-by: John Stanley <jpsinthemix@verizon.net>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 18 insertions, 6 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 5defc74973d7..600f6353ecf8 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1099,9 +1099,9 @@ static int ata_scsi_dev_config(struct scsi_device *sdev,
                 struct request_queue *q = sdev->request_queue;
                 void *buf;
 
-                /* set the min alignment and padding */
-                blk_queue_update_dma_alignment(sdev->request_queue,
-                                               ATA_DMA_PAD_SZ - 1);
+                sdev->sector_size = ATA_SECT_SIZE;
+
+                /* set DMA padding */
                 blk_queue_update_dma_pad(sdev->request_queue,
                                          ATA_DMA_PAD_SZ - 1);
 
@@ -1115,13 +1115,25 @@ static int ata_scsi_dev_config(struct scsi_device *sdev,
 
                 blk_queue_dma_drain(q, atapi_drain_needed, buf, ATAPI_MAX_DRAIN);
         } else {
-                /* ATA devices must be sector aligned */
                 sdev->sector_size = ata_id_logical_sector_size(dev->id);
-                blk_queue_update_dma_alignment(sdev->request_queue,
-                                               sdev->sector_size - 1);
                 sdev->manage_start_stop = 1;
         }
 
+        /*
+         * ata_pio_sectors() expects buffer for each sector to not cross
+         * page boundary.  Enforce it by requiring buffers to be sector
+         * aligned, which works iff sector_size is not larger than
+         * PAGE_SIZE.  ATAPI devices also need the alignment as
+         * IDENTIFY_PACKET is executed as ATA_PROT_PIO.
+         */
+        if (sdev->sector_size > PAGE_SIZE)
+                ata_dev_printk(dev, KERN_WARNING,
+                        "sector_size=%u > PAGE_SIZE, PIO may malfunction\n",
+                        sdev->sector_size);
+
+        blk_queue_update_dma_alignment(sdev->request_queue,
+                                       sdev->sector_size - 1);
+
         if (dev->flags & ATA_DFLAG_AN)
                 set_bit(SDEV_EVT_MEDIA_CHANGE, sdev->supported_events);