scsi: fix random memory corruption with scsi-mq + T10 PI

abattersby · Christoph Hellwig · commit 120bb3e1e36d · 2014-12-15T10:31:33.000+01:00
This fixes random memory corruption triggered when all three of the
following are true:

* scsi-mq enabled
* T10 Protection Information (DIF) enabled
* SCSI host with sg_tablesize &gt; SCSI_MAX_SG_SEGMENTS (128)

The symptoms of this bug are unpredictable memory corruption, BUG()s,
oopses, lockups, etc., any of which may appear to be completely
unrelated to the root cause.

Cc: &lt;stable@vger.kernel.org&gt; # 3.17.x, 3.18.x
Signed-off-by: Tony Battersby &lt;tonyb@cybernetics.com&gt;
Reviewed-by: Nicholas Bellinger &lt;nab@linux-iscsi.org&gt;
Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
@@ -1918,7 +1918,9 @@ static int scsi_mq_prep_fn(struct request *req)
 
 	if (scsi_host_get_prot(shost)) {
 		cmd->prot_sdb = (void *)sg +
-			shost->sg_tablesize * sizeof(struct scatterlist);
+			min_t(unsigned int,
+			      shost->sg_tablesize, SCSI_MAX_SG_SEGMENTS) *
+			sizeof(struct scatterlist);
 		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
 
 		cmd->prot_sdb->table.sgl =
