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Subject: Re: [PATCH 1/3] ext4: fix lost error code reporting in
 __ext4_fill_super()
To:     Theodore Ts'o <tytso@mit.edu>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>
CC:     Andreas Dilger <adilger@dilger.ca>,
        <syzbot+bbf0f9a213c94f283a5c@syzkaller.appspotmail.com>
References: <20230428031602.242297-1-tytso@mit.edu>
 <20230428031602.242297-2-tytso@mit.edu>
From:   Jason Yan <yanaijie@huawei.com>
Message-ID: <cd010dd6-7322-3711-73f3-deae4050017a@huawei.com>
Date:   Fri, 28 Apr 2023 11:35:15 +0800
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On 2023/4/28 11:16, Theodore Ts'o wrote:
> When code was factored out of __ext4_fill_super() into
> ext4_percpu_param_init() the error return was discard.  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() ...")
> Cc: Jason Yan <yanaijie@huawei.com>
> Link: https://syzkaller.appspot.com/bug?id=6dac47d5e58af770c0055f680369586ec32e144c
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> ---
>   fs/ext4/super.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 403cc0e6cd65..b11907e1fab2 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5503,7 +5503,8 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
>   		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))
> 

Reviewed-by: Jason Yan <yanaijie@huawei.com>