do not treat non-symlink reparse points as valid symlinks

Windows 8 and later can create NFS symlinks (within reparse points)
which we were assuming were normal NTFS symlinks and thus reporting
corrupt paths for.  Add check for reparse points to make sure that
they really are normal symlinks before we try to parse the pathname.

We also should not be parsing other types of reparse points (DFS
junctions etc) as if they were a  symlink so return EOPNOTSUPP
on those.  Also fix endian errors (we were not parsing symlink
lengths as little endian).

This fixes commit d244bf2dfbebfded05f494ffd53659fa7b1e32c1
which implemented follow link for non-Unix CIFS mounts

CC: Stable <stable@kernel.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 23 insertions, 8 deletions

diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
index a630475e421c..08f9dfb1a894 100644
--- a/fs/cifs/cifspdu.h
+++ b/fs/cifs/cifspdu.h
@@ -1491,15 +1491,30 @@ struct file_notify_information {
 	__u8  FileName[0];
 } __attribute__((packed));
 
-struct reparse_data {
-	__u32	ReparseTag;
-	__u16	ReparseDataLength;
+/* For IO_REPARSE_TAG_SYMLINK */
+struct reparse_symlink_data {
+	__le32	ReparseTag;
+	__le16	ReparseDataLength;
 	__u16	Reserved;
-	__u16	SubstituteNameOffset;
-	__u16	SubstituteNameLength;
-	__u16	PrintNameOffset;
-	__u16	PrintNameLength;
-	__u32	Flags;
+	__le16	SubstituteNameOffset;
+	__le16	SubstituteNameLength;
+	__le16	PrintNameOffset;
+	__le16	PrintNameLength;
+	__le32	Flags;
+	char	PathBuffer[0];
+} __attribute__((packed));
+
+/* For IO_REPARSE_TAG_NFS */
+#define NFS_SPECFILE_LNK	0x00000000014B4E4C
+#define NFS_SPECFILE_CHR	0x0000000000524843
+#define NFS_SPECFILE_BLK	0x00000000004B4C42
+#define NFS_SPECFILE_FIFO	0x000000004F464946
+#define NFS_SPECFILE_SOCK	0x000000004B434F53
+struct reparse_posix_data {
+	__le32	ReparseTag;
+	__le16	ReparseDataLength;
+	__u16	Reserved;
+	__le64	InodeType; /* LNK, FIFO, CHR etc. */
 	char	PathBuffer[0];
 } __attribute__((packed));