cifs: use get/put_unaligned functions to access ByteCount

It's possible that when we access the ByteCount that the alignment
will be off. Most CPUs deal with that transparently, but there's
usually some performance impact. Some CPUs raise an exception on
unaligned accesses.

Fix this by accessing the byte count using the get_unaligned and
put_unaligned inlined functions. While we're at it, fix the types
of some of the variables that end up getting returns from these
functions.

Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 43 insertions, 4 deletions

diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
index ea205b4..b5c8cc5 100644
--- a/fs/cifs/cifspdu.h
+++ b/fs/cifs/cifspdu.h
@@ -23,6 +23,7 @@
 #define _CIFSPDU_H
 
 #include <net/sock.h>
+#include <asm/unaligned.h>
 #include "smbfsctl.h"
 
 #ifdef CONFIG_CIFS_WEAK_PW_HASH
@@ -426,11 +427,49 @@ struct smb_hdr {
 	__u16 Mid;
 	__u8 WordCount;
 } __attribute__((packed));
-/* given a pointer to an smb_hdr retrieve the value of byte count */
-#define BCC(smb_var) (*(__u16 *)((char *)(smb_var) + sizeof(struct smb_hdr) + (2 * (smb_var)->WordCount)))
-#define BCC_LE(smb_var) (*(__le16 *)((char *)(smb_var) + sizeof(struct smb_hdr) + (2 * (smb_var)->WordCount)))
+
+/* given a pointer to an smb_hdr retrieve a char pointer to the byte count */
+#define BCC(smb_var) ((unsigned char *)(smb_var) + sizeof(struct smb_hdr) + \
+			 (2 * (smb_var)->WordCount))
+
 /* given a pointer to an smb_hdr retrieve the pointer to the byte area */
-#define pByteArea(smb_var) ((unsigned char *)(smb_var) + sizeof(struct smb_hdr) + (2 * (smb_var)->WordCount) + 2)
+#define pByteArea(smb_var) (BCC(smb_var) + 2)
+
+/* get the converted ByteCount for a SMB packet and return it */
+static inline __u16
+get_bcc(struct smb_hdr *hdr)
+{
+	__u16 *bc_ptr = (__u16 *)BCC(hdr);
+
+	return get_unaligned(bc_ptr);
+}
+
+/* get the unconverted ByteCount for a SMB packet and return it */
+static inline __u16
+get_bcc_le(struct smb_hdr *hdr)
+{
+	__le16 *bc_ptr = (__le16 *)BCC(hdr);
+
+	return get_unaligned_le16(bc_ptr);
+}
+
+/* set the ByteCount for a SMB packet in host-byte order */
+static inline void
+put_bcc(__u16 count, struct smb_hdr *hdr)
+{
+	__u16 *bc_ptr = (__u16 *)BCC(hdr);
+
+	put_unaligned(count, bc_ptr);
+}
+
+/* set the ByteCount for a SMB packet in little-endian */
+static inline void
+put_bcc_le(__u16 count, struct smb_hdr *hdr)
+{
+	__le16 *bc_ptr = (__le16 *)BCC(hdr);
+
+	put_unaligned_le16(count, bc_ptr);
+}
 
 /*
  * Computer Name Length (since Netbios name was length 16 with last byte 0x20)