scsi: core: fix the dma_max_mapping_size call

We should only call dma_max_mapping_size for devices that have a DMA mask
set, otherwise we can run into a NULL pointer dereference that will crash
the system.

Also we need to do right shift to get the sectors from the size in bytes,
not a left shift.

Fixes: bdd17bdef7d8 ("scsi: core: take the DMA max mapping size into account")
Reported-by: Bart Van Assche <bvanassche@acm.org>
Reported-by: Ming Lei <tom.leiming@gmail.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@canonical.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9381171c2fc02741df68aa59b9e8a024f608356a..11e64b50497f81949476014f2b31d40d024346ed 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1784,8 +1784,10 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
                blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
        }
 
-       shost->max_sectors = min_t(unsigned int, shost->max_sectors,
-                       dma_max_mapping_size(dev) << SECTOR_SHIFT);
+       if (dev->dma_mask) {
+               shost->max_sectors = min_t(unsigned int, shost->max_sectors,
+                               dma_max_mapping_size(dev) >> SECTOR_SHIFT);
+       }
        blk_queue_max_hw_sectors(q, shost->max_sectors);
        if (shost->unchecked_isa_dma)
                blk_queue_bounce_limit(q, BLK_BOUNCE_ISA);