cifs_atomic_open(): fix double-put on late allocation failure

commit d9a9f4849fe0c9d560851ab22a85a666cddfdd24 upstream.

several iterations of ->atomic_open() calling conventions ago, we
used to need fput() if ->atomic_open() failed at some point after
successful finish_open().  Now (since 2016) it's not needed -
struct file carries enough state to make fput() work regardless
of the point in struct file lifecycle and discarding it on
failure exits in open() got unified.  Unfortunately, I'd missed
the fact that we had an instance of ->atomic_open() (cifs one)
that used to need that fput(), as well as the stale comment in
finish_open() demanding such late failure handling.  Trivially
fixed...

Fixes: fe9ec8291fca "do_last(): take fput() on error after opening to out:"
Cc: stable@kernel.org # v4.7+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 93e0a24045322b3e2417e024821520c9996eb6fc..c757c1c3cb814b2b1f5c565fd1c6551fa05d3b46 100644 (file)
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -606,3 +606,10 @@ in your dentry operations instead.
        dentry separately, and it now has request_mask and query_flags arguments
        to specify the fields and sync type requested by statx.  Filesystems not
        supporting any statx-specific features may ignore the new arguments.
+--
+[mandatory]
+
+       [should've been added in 2016] stale comment in finish_open()
+       nonwithstanding, failure exits in ->atomic_open() instances should
+       *NOT* fput() the file, no matter what.  Everything is handled by the
+       caller.

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index f00a7ce3eb6e4fa86f3c24bfeef291f7fbf17828..03293e543c075a2f41911b7f679b91178035af9f 100644 (file)
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -562,7 +562,6 @@ cifs_atomic_open(struct inode *inode, struct dentry *direntry,
                if (server->ops->close)
                        server->ops->close(xid, tcon, &fid);
                cifs_del_pending_open(&open);
-               fput(file);
                rc = -ENOMEM;
        }
 

diff --git a/fs/open.c b/fs/open.c
index 29a2cdcbcb1791eaf3fc5d229753c1ca72ac3d72..49fd070be0ec2afe52a46490735de7e7a1ebabe0 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -824,9 +824,6 @@ cleanup_file:
  * the return value of d_splice_alias(), then the caller needs to perform dput()
  * on it after finish_open().
  *
- * On successful return @file is a fully instantiated open file.  After this, if
- * an error occurs in ->atomic_open(), it needs to clean up with fput().
- *
  * Returns zero on success or -errno if the open failed.
  */
 int finish_open(struct file *file, struct dentry *dentry,