cifs: Replace wrtPending with a real reference count

Currently, cifs_close() tries to wait until all I/O is complete and then
frees the file private data.  If I/O does not completely in a reasonable
amount of time it frees the structure anyway, leaving a potential use-
after-free situation.

This patch changes the wrtPending counter to a complete reference count and
lets the last user free the structure.

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Tested-by: Shirish Pargaonkar <shirishp@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 82d83839655e..1f09c7619319 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -800,7 +800,7 @@ set_via_filehandle:
         if (open_file == NULL)
                 CIFSSMBClose(xid, pTcon, netfid);
         else
-                atomic_dec(&open_file->wrtPending);
+                cifsFileInfo_put(open_file);
 out:
         return rc;
 }
@@ -1635,7 +1635,7 @@ cifs_set_file_size(struct inode *inode, struct iattr *attrs,
                 __u32 npid = open_file->pid;
                 rc = CIFSSMBSetFileSize(xid, pTcon, attrs->ia_size, nfid,
                                         npid, false);
-                atomic_dec(&open_file->wrtPending);
+                cifsFileInfo_put(open_file);
                 cFYI(1, ("SetFSize for attrs rc = %d", rc));
                 if ((rc == -EINVAL) || (rc == -EOPNOTSUPP)) {
                         unsigned int bytes_written;
@@ -1790,7 +1790,7 @@ cifs_setattr_unix(struct dentry *direntry, struct iattr *attrs)
                 u16 nfid = open_file->netfid;
                 u32 npid = open_file->pid;
                 rc = CIFSSMBUnixSetFileInfo(xid, pTcon, args, nfid, npid);
-                atomic_dec(&open_file->wrtPending);
+                cifsFileInfo_put(open_file);
         } else {
                 rc = CIFSSMBUnixSetPathInfo(xid, pTcon, full_path, args,
                                     cifs_sb->local_nls,