[SCSI] srp.h: avoid padding of structs

Several structs in <scsi/srp.h> get padded to a multiple of 8 bytes on
64-bit architectures and end up with a size that does not match the
definition in the SRP spec:

                                     SRP spec     64-bit
    sizeof (struct indirect_buf)        20          24
    sizeof (struct srp_login_rsp)       52          56
    sizeof (struct srp_rsp)             36          40

Fix this by adding __attribute__((packed)) to the offending structs.

Problem pointed out by Arne Redlich <arne.redlich@xiranet.com>.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/include/scsi/srp.h b/include/scsi/srp.h
index 6c2681dc5b46..637f77eccf0c 100644
--- a/include/scsi/srp.h
+++ b/include/scsi/srp.h
@@ -95,14 +95,15 @@ struct srp_direct_buf {
 
 /*
  * We need the packed attribute because the SRP spec puts the list of
- * descriptors at an offset of 20, which is not aligned to the size
- * of struct srp_direct_buf.
+ * descriptors at an offset of 20, which is not aligned to the size of
+ * struct srp_direct_buf.  The whole structure must be packed to avoid
+ * having the 20-byte structure padded to 24 bytes on 64-bit architectures.
  */
 struct srp_indirect_buf {
         struct srp_direct_buf   table_desc;
         __be32                  len;
-        struct srp_direct_buf   desc_list[0] __attribute__((packed));
-};
+        struct srp_direct_buf   desc_list[0];
+} __attribute__((packed));
 
 enum {
         SRP_MULTICHAN_SINGLE = 0,
@@ -122,6 +123,11 @@ struct srp_login_req {
         u8      target_port_id[16];
 };
 
+/*
+ * The SRP spec defines the size of the LOGIN_RSP structure to be 52
+ * bytes, so it needs to be packed to avoid having it padded to 56
+ * bytes on 64-bit architectures.
+ */
 struct srp_login_rsp {
         u8      opcode;
         u8      reserved1[3];
@@ -132,7 +138,7 @@ struct srp_login_rsp {
         __be16  buf_fmt;
         u8      rsp_flags;
         u8      reserved2[25];
-};
+} __attribute__((packed));
 
 struct srp_login_rej {
         u8      opcode;
@@ -207,6 +213,11 @@ enum {
         SRP_RSP_FLAG_DIUNDER  = 1 << 5
 };
 
+/*
+ * The SRP spec defines the size of the RSP structure to be 36 bytes,
+ * so it needs to be packed to avoid having it padded to 40 bytes on
+ * 64-bit architectures.
+ */
 struct srp_rsp {
         u8      opcode;
         u8      sol_not;
@@ -221,6 +232,6 @@ struct srp_rsp {
         __be32  sense_data_len;
         __be32  resp_data_len;
         u8      data[0];
-};
+} __attribute__((packed));
 
 #endif /* SCSI_SRP_H */