target/file: Fix BUG() when CONFIG_DEBUG_SG=y and DIF protection enabled

When CONFIG_DEBUG_SG=y and DIF protection support enabled, kernel
BUG()s are triggered due to the following two issues:

1) prot_sg is not initialized by sg_init_table().

When CONFIG_DEBUG_SG=y, scatterlist helpers check sg entry has a
correct magic value.

2) vmalloc'ed buffer is passed to sg_set_buf().

sg_set_buf() uses virt_to_page() to convert virtual address to struct
page, but it doesn't work with vmalloc address.  vmalloc_to_page()
should be used instead.  As prot_buf isn't usually too large, so
fix it by allocating prot_buf by kmalloc instead of vmalloc.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: <stable@vger.kernel.org> # v3.14+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_file.c

@@ -274,7 +274,7 @@ static int fd_do_prot_rw(struct se_cmd *cmd, struct fd_prot *fd_prot,
 		     se_dev->prot_length;
 
 	if (!is_write) {
-		fd_prot->prot_buf = vzalloc(prot_size);
+		fd_prot->prot_buf = kzalloc(prot_size, GFP_KERNEL);
 		if (!fd_prot->prot_buf) {
 			pr_err("Unable to allocate fd_prot->prot_buf\n");
 			return -ENOMEM;
@@ -286,9 +286,10 @@ static int fd_do_prot_rw(struct se_cmd *cmd, struct fd_prot *fd_prot,
 					   fd_prot->prot_sg_nents, GFP_KERNEL);
 		if (!fd_prot->prot_sg) {
 			pr_err("Unable to allocate fd_prot->prot_sg\n");
-			vfree(fd_prot->prot_buf);
+			kfree(fd_prot->prot_buf);
 			return -ENOMEM;
 		}
+		sg_init_table(fd_prot->prot_sg, fd_prot->prot_sg_nents);
 		size = prot_size;
 
 		for_each_sg(fd_prot->prot_sg, sg, fd_prot->prot_sg_nents, i) {
@@ -318,7 +319,7 @@ static int fd_do_prot_rw(struct se_cmd *cmd, struct fd_prot *fd_prot,
 
 	if (is_write || ret < 0) {
 		kfree(fd_prot->prot_sg);
-		vfree(fd_prot->prot_buf);
+		kfree(fd_prot->prot_buf);
 	}
 
 	return ret;
@@ -599,11 +600,11 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 						 0, fd_prot.prot_sg, 0);
 			if (rc) {
 				kfree(fd_prot.prot_sg);
-				vfree(fd_prot.prot_buf);
+				kfree(fd_prot.prot_buf);
 				return rc;
 			}
 			kfree(fd_prot.prot_sg);
-			vfree(fd_prot.prot_buf);
+			kfree(fd_prot.prot_buf);
 		}
 	} else {
 		memset(&fd_prot, 0, sizeof(struct fd_prot));
@@ -619,7 +620,7 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 						  0, fd_prot.prot_sg, 0);
 			if (rc) {
 				kfree(fd_prot.prot_sg);
-				vfree(fd_prot.prot_buf);
+				kfree(fd_prot.prot_buf);
 				return rc;
 			}
 		}
@@ -655,7 +656,7 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 
 	if (ret < 0) {
 		kfree(fd_prot.prot_sg);
-		vfree(fd_prot.prot_buf);
+		kfree(fd_prot.prot_buf);
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 	}