[PATCH v2 20/23] binfmt_misc: use __free(kfree) in bm_register_write()

[Christian Brauner <brauner@kernel.org>]

bm_register_write() has to free the entry it got from create_entry()
on every failure until add_entry() has linked it into the filesystem
and made the inode its owner. Arm the entry with __free(kfree) so the
error branches can simply return and disarm it via
retain_and_null_ptr() once ownership has been handed to the inode.
The interpreter file keeps its manual error cleanup as freeing the
entry would not close it.

No functional change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/binfmt_misc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index c2d947f934ab..6acce58ce405 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -796,13 +796,12 @@ static int add_entry(struct binfmt_misc_entry *e, struct super_block *sb)
 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 			       size_t count, loff_t *ppos)
 {
-	struct binfmt_misc_entry *e;
+	struct binfmt_misc_entry *e __free(kfree) = NULL;
 	struct super_block *sb = file_inode(file)->i_sb;
-	int err = 0;
 	struct file *f = NULL;
+	int err;
 
 	e = create_entry(buffer, count);
-
 	if (IS_ERR(e))
 		return PTR_ERR(e);
 
@@ -819,7 +818,6 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 		if (IS_ERR(f)) {
 			pr_notice("register: failed to install interpreter file %s\n",
 				 e->interpreter);
-			kfree(e);
 			return PTR_ERR(f);
 		}
 		e->interp_file = f;
@@ -831,9 +829,11 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 			exe_file_allow_write_access(f);
 			filp_close(f, NULL);
 		}
-		kfree(e);
 		return err;
 	}
+
+	/* The entry is owned by its inode now. */
+	retain_and_null_ptr(e);
 	return count;
 }
 

-- 
2.53.0