Re: [PATCH 1/2] scsi: fix max discard sectors calculation

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On 05/16/2016 11:46 AM, mchristi@xxxxxxxxxx wrote:
logical_block_size and max_blocks are 32 bits, so we can
overflow when trying to convert SCSI device blocks to linux
block layer sectors.

Signed-off-by: Mike Christie <mchristi@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx

---
  drivers/scsi/sd.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index f52b74c..1668e1d 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -690,7 +690,8 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
-	blk_queue_max_discard_sectors(q, max_blocks * (logical_block_size >> 9));
+	blk_queue_max_discard_sectors(q, (u64)max_blocks *
+				      (logical_block_size >> 9));

Hello Mike,

As far as I can see max_blocks <= 0xffff (SD_MAX_WS10_BLOCKS) and 512 <= logical_block_size <= 4096. How can max_blocks * (logical_block_size >> 9) be too large for a 32 bit integer?

Thanks,

Bart.
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