scsi: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare variable-length
types such as these ones is a flexible array member[1][2], introduced in
C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by this
change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Link: https://lore.kernel.org/r/20200224161406.GA21454@embeddedor
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/include/scsi/iscsi_if.h b/include/scsi/iscsi_if.h
index 92b11c7e0b4f..b0e240b10bf9 100644
--- a/include/scsi/iscsi_if.h
+++ b/include/scsi/iscsi_if.h
@@ -311,7 +311,7 @@ enum iscsi_param_type {
 struct iscsi_param_info {
 	uint32_t len;		/* Actual length of the param value */
 	uint16_t param;		/* iscsi param */
-	uint8_t value[0];	/* length sized value follows */
+	uint8_t value[];	/* length sized value follows */
 } __packed;
 
 struct iscsi_iface_param_info {
@@ -320,7 +320,7 @@ struct iscsi_iface_param_info {
 	uint16_t param;		/* iscsi param value */
 	uint8_t iface_type;	/* IPv4 or IPv6 */
 	uint8_t param_type;	/* iscsi_param_type */
-	uint8_t value[0];	/* length sized value follows */
+	uint8_t value[];	/* length sized value follows */
 } __packed;
 
 /*
@@ -697,7 +697,7 @@ enum iscsi_flashnode_param {
 struct iscsi_flashnode_param_info {
 	uint32_t len;		/* Actual length of the param */
 	uint16_t param;		/* iscsi param value */
-	uint8_t value[0];	/* length sized value follows */
+	uint8_t value[];	/* length sized value follows */
 } __packed;
 
 enum iscsi_discovery_parent_type {
@@ -815,7 +815,7 @@ struct iscsi_stats {
 	 * up to ISCSI_STATS_CUSTOM_MAX
 	 */
 	uint32_t custom_length;
-	struct iscsi_stats_custom custom[0]
+	struct iscsi_stats_custom custom[]
 		__attribute__ ((aligned (sizeof(uint64_t))));
 };
 
@@ -946,7 +946,7 @@ struct iscsi_offload_host_stats {
 	 * up to ISCSI_HOST_STATS_CUSTOM_MAX
 	 */
 	uint32_t custom_length;
-	struct iscsi_host_stats_custom custom[0]
+	struct iscsi_host_stats_custom custom[]
 		__aligned(sizeof(uint64_t));
 };