scsi: libsas: Introduce struct smp_disc_resp

When compiling with gcc 12, several warnings are thrown by gcc when
compiling drivers/scsi/libsas/sas_expander.c, e.g.:

In function ‘sas_get_phy_change_count’,
    inlined from ‘sas_find_bcast_phy.constprop’ at
drivers/scsi/libsas/sas_expander.c:1737:9:
drivers/scsi/libsas/sas_expander.c:1697:39: warning: array subscript
‘struct smp_resp[0]’ is partly outside array bounds of ‘unsigned
char[56]’ [-Warray-bounds]
 1697 |                 *pcc = disc_resp->disc.change_count;
      |                        ~~~~~~~~~~~~~~~^~~~~~~~~~~~~

This is due to the use of the struct smp_resp to aggregate all possible
response types using a union but allocating a response buffer with a size
exactly equal to the size of the response type needed. This leads to access
to fields of struct smp_resp from an allocated memory area that is smaller
than the size of struct smp_resp.

Fix this by defining struct smp_disc_resp for sas discovery operations.
Since this structure and the generic struct smp_resp are identical for
the little endian and big endian archs, move the definition of these
structures at the end of include/scsi/sas.h to avoid repeating their
definition.

Link: https://lore.kernel.org/r/20220609022456.409087-2-damien.lemoal@opensource.wdc.com
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 12 insertions, 16 deletions

diff --git a/include/scsi/sas.h b/include/scsi/sas.h
index acfc69fd72d0..b3ee9bd63277 100644
--- a/include/scsi/sas.h
+++ b/include/scsi/sas.h
@@ -471,18 +471,6 @@ struct report_phy_sata_resp {
 	__be32 crc;
 } __attribute__ ((packed));
 
-struct smp_resp {
-	u8    frame_type;
-	u8    function;
-	u8    result;
-	u8    reserved;
-	union {
-		struct report_general_resp  rg;
-		struct discover_resp        disc;
-		struct report_phy_sata_resp rps;
-	};
-} __attribute__ ((packed));
-
 #elif defined(__BIG_ENDIAN_BITFIELD)
 struct sas_identify_frame {
 	/* Byte 0 */
@@ -704,6 +692,18 @@ struct report_phy_sata_resp {
 	__be32 crc;
 } __attribute__ ((packed));
 
+#else
+#error "Bitfield order not defined!"
+#endif
+
+struct smp_disc_resp {
+	u8    frame_type;
+	u8    function;
+	u8    result;
+	u8    reserved;
+	struct discover_resp disc;
+} __attribute__ ((packed));
+
 struct smp_resp {
 	u8    frame_type;
 	u8    function;
@@ -716,8 +716,4 @@ struct smp_resp {
 	};
 } __attribute__ ((packed));
 
-#else
-#error "Bitfield order not defined!"
-#endif
-
 #endif /* _SAS_H_ */