Target/sbc: Don't use sg as iterator in sbc_verify_read

Because then this sg is passed to sbc_copy_prot which will
hit a protection fault in cases we have more than a single sg.
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_sbc.c

@@ -1162,7 +1162,7 @@ sbc_dif_verify_read(struct se_cmd *cmd, sector_t start, unsigned int sectors,
 {
 	struct se_device *dev = cmd->se_dev;
 	struct se_dif_v1_tuple *sdt;
-	struct scatterlist *dsg;
+	struct scatterlist *dsg, *psg = sg;
 	sector_t sector = start;
 	void *daddr, *paddr;
 	int i, j, offset = sg_off;
@@ -1170,14 +1170,14 @@ sbc_dif_verify_read(struct se_cmd *cmd, sector_t start, unsigned int sectors,
 
 	for_each_sg(cmd->t_data_sg, dsg, cmd->t_data_nents, i) {
 		daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
-		paddr = kmap_atomic(sg_page(sg)) + sg->offset;
+		paddr = kmap_atomic(sg_page(psg)) + sg->offset;
 
 		for (j = 0; j < dsg->length; j += dev->dev_attrib.block_size) {
 
-			if (offset >= sg->length) {
+			if (offset >= psg->length) {
 				kunmap_atomic(paddr);
-				sg = sg_next(sg);
-				paddr = kmap_atomic(sg_page(sg)) + sg->offset;
+				psg = sg_next(psg);
+				paddr = kmap_atomic(sg_page(psg)) + psg->offset;
 				offset = 0;
 			}