cifs: implement CIFSCouldBeMFSymlink() and CIFSCheckMFSymlink()

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>

2 files changed, 83 insertions, 0 deletions

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 588612867451..8604a45c1107 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -409,4 +409,8 @@ extern int CIFSSMBSetPosixACL(const int xid, struct cifsTconInfo *tcon,
 extern int CIFSGetExtAttr(const int xid, struct cifsTconInfo *tcon,
                         const int netfid, __u64 *pExtAttrBits, __u64 *pMask);
 extern void cifs_autodisable_serverino(struct cifs_sb_info *cifs_sb);
+extern bool CIFSCouldBeMFSymlink(const struct cifs_fattr *fattr);
+extern int CIFSCheckMFSymlink(struct cifs_fattr *fattr,
+                const unsigned char *path,
+                struct cifs_sb_info *cifs_sb, int xid);
 #endif                  /* _CIFSPROTO_H */
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 12eb491d4c52..bec212b09a02 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -91,6 +91,85 @@ CIFSParseMFSymlink(const u8 *buf,
         return 0;
 }
 
+bool
+CIFSCouldBeMFSymlink(const struct cifs_fattr *fattr)
+{
+        if (!(fattr->cf_mode & S_IFREG))
+                /* it's not a symlink */
+                return false;
+
+        if (fattr->cf_eof != CIFS_MF_SYMLINK_FILE_SIZE)
+                /* it's not a symlink */
+                return false;
+
+        return true;
+}
+
+int
+CIFSCheckMFSymlink(struct cifs_fattr *fattr,
+                   const unsigned char *path,
+                   struct cifs_sb_info *cifs_sb, int xid)
+{
+        int rc;
+        int oplock = 0;
+        __u16 netfid = 0;
+        struct cifsTconInfo *pTcon = cifs_sb->tcon;
+        u8 *buf;
+        char *pbuf;
+        unsigned int bytes_read = 0;
+        int buf_type = CIFS_NO_BUFFER;
+        unsigned int link_len = 0;
+        FILE_ALL_INFO file_info;
+
+        if (!CIFSCouldBeMFSymlink(fattr))
+                /* it's not a symlink */
+                return 0;
+
+        rc = CIFSSMBOpen(xid, pTcon, path, FILE_OPEN, GENERIC_READ,
+                         CREATE_NOT_DIR, &netfid, &oplock, &file_info,
+                         cifs_sb->local_nls,
+                         cifs_sb->mnt_cifs_flags &
+                                CIFS_MOUNT_MAP_SPECIAL_CHR);
+        if (rc != 0)
+                return rc;
+
+        if (file_info.EndOfFile != CIFS_MF_SYMLINK_FILE_SIZE) {
+                CIFSSMBClose(xid, pTcon, netfid);
+                /* it's not a symlink */
+                return 0;
+        }
+
+        buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
+        pbuf = buf;
+
+        rc = CIFSSMBRead(xid, pTcon, netfid,
+                         CIFS_MF_SYMLINK_FILE_SIZE /* length */,
+                         0 /* offset */,
+                         &bytes_read, &pbuf, &buf_type);
+        CIFSSMBClose(xid, pTcon, netfid);
+        if (rc != 0) {
+                kfree(buf);
+                return rc;
+        }
+
+        rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, NULL);
+        kfree(buf);
+        if (rc == -EINVAL)
+                /* it's not a symlink */
+                return 0;
+        if (rc != 0)
+                return rc;
+
+        /* it is a symlink */
+        fattr->cf_eof = link_len;
+        fattr->cf_mode &= ~S_IFMT;
+        fattr->cf_mode |= S_IFLNK | S_IRWXU | S_IRWXG | S_IRWXO;
+        fattr->cf_dtype = DT_LNK;
+        return 0;
+}
+
 int
 cifs_hardlink(struct dentry *old_file, struct inode *inode,
               struct dentry *direntry)