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

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 > 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: <stable@vger.kernel.org> # 3.17.x, 3.18.x
Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 43318d556cbcf28209f317e0c3646923324e6127..9ea95dd3e2604eea2613a5a15d074c2357fac7dd 100644 (file)
--- 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 =