cifs: We do not drop reference to tlink in CIFSCheckMFSymlink()

When we obtain tcon from cifs_sb, we use cifs_sb_tlink() to first obtain
tlink which also grabs a reference to it. We do not drop this reference
to tlink once we are done with the call.

The patch fixes this issue by instead passing tcon as a parameter and
avoids having to obtain a reference to the tlink. A lookup for the tcon
is already made in the calling functions and this way we avoid having to
re-run the lookup. This is also consistent with the argument list for
other similar calls for M-F symlinks.

We should also return an ENOSYS when we do not find a protocol specific
function to lookup the MF Symlink data.

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
CC: Stable <stable@kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>

3 files changed, 19 insertions, 20 deletions

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index aa3397620342..2c29db6a247e 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -477,9 +477,10 @@ extern int CIFSGetExtAttr(const unsigned int xid, struct cifs_tcon *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, unsigned int xid);
+extern int CIFSCheckMFSymlink(unsigned int xid, struct cifs_tcon *tcon,
+                              struct cifs_sb_info *cifs_sb,
+                              struct cifs_fattr *fattr,
+                              const unsigned char *path);
 extern int mdfour(unsigned char *, unsigned char *, int);
 extern int E_md4hash(const unsigned char *passwd, unsigned char *p16,
                         const struct nls_table *codepage);
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 36f9ebb93ceb..49719b8228e5 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -383,7 +383,8 @@ int cifs_get_inode_info_unix(struct inode **pinode,
 
         /* check for Minshall+French symlinks */
         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) {
-                int tmprc = CIFSCheckMFSymlink(&fattr, full_path, cifs_sb, xid);
+                int tmprc = CIFSCheckMFSymlink(xid, tcon, cifs_sb, &fattr,
+                                               full_path);
                 if (tmprc)
                         cifs_dbg(FYI, "CIFSCheckMFSymlink: %d\n", tmprc);
         }
@@ -799,7 +800,8 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 
         /* check for Minshall+French symlinks */
         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) {
-                tmprc = CIFSCheckMFSymlink(&fattr, full_path, cifs_sb, xid);
+                tmprc = CIFSCheckMFSymlink(xid, tcon, cifs_sb, &fattr,
+                                           full_path);
                 if (tmprc)
                         cifs_dbg(FYI, "CIFSCheckMFSymlink: %d\n", tmprc);
         }
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index cc0234710ddb..92aee08483a5 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -354,34 +354,30 @@ open_query_close_cifs_symlink(const unsigned char *path, char *pbuf,
 
 
 int
-CIFSCheckMFSymlink(struct cifs_fattr *fattr,
-                   const unsigned char *path,
-                   struct cifs_sb_info *cifs_sb, unsigned int xid)
+CIFSCheckMFSymlink(unsigned int xid, struct cifs_tcon *tcon,
+                   struct cifs_sb_info *cifs_sb, struct cifs_fattr *fattr,
+                   const unsigned char *path)
 {
-        int rc = 0;
+        int rc;
         u8 *buf = NULL;
         unsigned int link_len = 0;
         unsigned int bytes_read = 0;
-        struct cifs_tcon *ptcon;
 
         if (!CIFSCouldBeMFSymlink(fattr))
                 /* it's not a symlink */
                 return 0;
 
         buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
-        if (!buf) {
-                rc = -ENOMEM;
-                goto out;
-        }
+        if (!buf)
+                return -ENOMEM;
 
-        ptcon = tlink_tcon(cifs_sb_tlink(cifs_sb));
-        if ((ptcon->ses) && (ptcon->ses->server->ops->query_mf_symlink))
-                rc = ptcon->ses->server->ops->query_mf_symlink(path, buf,
-                                                 &bytes_read, cifs_sb, xid);
+        if (tcon->ses->server->ops->query_mf_symlink)
+                rc = tcon->ses->server->ops->query_mf_symlink(path, buf,
+                                                &bytes_read, cifs_sb, xid);
         else
-                goto out;
+                rc = -ENOSYS;
 
-        if (rc != 0)
+        if (rc)
                 goto out;
 
         if (bytes_read == 0) /* not a symlink */