fs: move cleanup from init_file() into its callers

The use of file_free_rcu() in init_file() to free the struct that was
allocated by the caller was hacky and we got what we deserved.

Let init_file() and its callers take care of cleaning up each after
their own allocated resources on error.

Fixes: 62d53c4 ("fs: use backing_file container for internal files with "fake" f_path") # mainline only
Reported-and-tested-by: syzbot+ada42aab05cf51b00e98@syzkaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Message-Id: <20230701171134.239409-1-amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/file_table.c

@@ -160,7 +160,7 @@ static int init_file(struct file *f, int flags, const struct cred *cred)
 	f->f_cred = get_cred(cred);
 	error = security_file_alloc(f);
 	if (unlikely(error)) {
-		file_free_rcu(&f->f_rcuhead);
+		put_cred(f->f_cred);
 		return error;
 	}
 
@@ -208,8 +208,10 @@ struct file *alloc_empty_file(int flags, const struct cred *cred)
 		return ERR_PTR(-ENOMEM);
 
 	error = init_file(f, flags, cred);
-	if (unlikely(error))
+	if (unlikely(error)) {
+		kmem_cache_free(filp_cachep, f);
 		return ERR_PTR(error);
+	}
 
 	percpu_counter_inc(&nr_files);
 
@@ -240,8 +242,10 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
 		return ERR_PTR(-ENOMEM);
 
 	error = init_file(f, flags, cred);
-	if (unlikely(error))
+	if (unlikely(error)) {
+		kmem_cache_free(filp_cachep, f);
 		return ERR_PTR(error);
+	}
 
 	f->f_mode |= FMODE_NOACCOUNT;
 
@@ -265,8 +269,10 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred)
 		return ERR_PTR(-ENOMEM);
 
 	error = init_file(&ff->file, flags, cred);
-	if (unlikely(error))
+	if (unlikely(error)) {
+		kfree(ff);
 		return ERR_PTR(error);
+	}
 
 	ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT;
 	return &ff->file;