[PATCH 6.1 310/312] ext4: fix lost error code reporting in __ext4_fill_super()

Greg Kroah-Hartman
2026-04-08T18:20:11Z

From: Theodore Ts'o <tytso@mit.edu>

commit d5e72c4e3256335d6fb75c2e321144f93141f4f5 upstream.

When code was factored out of __ext4_fill_super() into
ext4_percpu_param_init() the error return was discarded. This meant
that it was possible for __ext4_fill_super() to return zero,
indicating success, without the struct super getting completely filled
in, leading to a potential NULL pointer dereference.

Reported-by: syzbot+bbf0f9a213c94f283a5c@syzkaller.appspotmail.com
Fixes: 1f79467c8a6b ("ext4: factor out ext4_percpu_param_init() ...")
Link: https://syzkaller.appspot.com/bug?id=6dac47d5e58af770c0055f680369586ec32e144c
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5531,7 +5531,8 @@ static int __ext4_fill_super(struct fs_c
sbi->s_journal->j_commit_callback =
ext4_journal_commit_callback;

- if (ext4_percpu_param_init(sbi))
+ err = ext4_percpu_param_init(sbi);
+ if (err)
goto failed_mount6;

if (ext4_has_feature_flex_bg(sb))