cifs: fix dentry refcount leak when opening a FIFO on lookup

commit 5bccda0ebc7c0331b81ac47d39e4b920b198b2cd upstream.

The cifs code will attempt to open files on lookup under certain
circumstances. What happens though if we find that the file we opened
was actually a FIFO or other special file?

Currently, the open filehandle just ends up being leaked leading to
a dentry refcount mismatch and oops on umount. Fix this by having the
code close the filehandle on the server if it turns out not to be a
regular file. While we're at it, change this spaghetti if statement
into a switch too.

Reported-by: CAI Qian <caiqian@redhat.com>
Tested-by: CAI Qian <caiqian@redhat.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index ff3d891f49b92fc63b35824a1b6d51432c5dc649..fc79b957f3122657bbbceb33e10cd4531eb4c037 100644 (file)
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -692,10 +692,26 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
                         * If either that or op not supported returned, follow
                         * the normal lookup.
                         */
-                       if ((rc == 0) || (rc == -ENOENT))
+                       switch (rc) {
+                       case 0:
+                               /*
+                                * The server may allow us to open things like
+                                * FIFOs, but the client isn't set up to deal
+                                * with that. If it's not a regular file, just
+                                * close it and proceed as if it were a normal
+                                * lookup.
+                                */
+                               if (newInode && !S_ISREG(newInode->i_mode)) {
+                                       CIFSSMBClose(xid, pTcon, fileHandle);
+                                       break;
+                               }
+                       case -ENOENT:
                                posix_open = true;
-                       else if ((rc == -EINVAL) || (rc != -EOPNOTSUPP))
+                       case -EOPNOTSUPP:
+                               break;
+                       default:
                                pTcon->broken_posix_open = true;
+                       }
                }
                if (!posix_open)
                        rc = cifs_get_inode_info_unix(&newInode, full_path,