linux-kernel - Re: [PATCH] exfat: fix refcount leak in exfat

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Message-ID:
 <PUZPR04MB6316F58807941F86C2769FCC81F2A@PUZPR04MB6316.apcprd04.prod.outlook.com>
Date: Tue, 21 Oct 2025 08:21:57 +0000
From: "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To: Shuhao Fu <sfual@....ust.hk>
CC: Namjae Jeon <linkinjeon@...nel.org>,
        Sungjong Seo
	<sj1557.seo@...sung.com>,
        "linux-fsdevel@...r.kernel.org"
	<linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] exfat: fix refcount leak in exfat_find

On Tue, Oct 21, 2025 16:04 Shuhao Fu <sfual@....ust.hk> wrote:
> On Tue, Oct 21, 2025 at 01:38:29AM +0000, Yuezhang.Mo@...y.com wrote:
> > On Mon, Oct 20, 2025 23:00 Shuhao Fu <sfual@....ust.hk> wrote:
> > 
> > I think it would be better to move these checks after exfat_put_dentry_set().
> > Because the following check will correct ->valid_size and ->size.
> > 
> >         if (!is_valid_cluster(sbi, info->start_clu) && info->size) {
> >                 exfat_warn(sb, "start_clu is invalid cluster(0x%x)",
> >                                 info->start_clu);
> >                 info->size = 0;
> >                 info->valid_size = 0;
> >         }
> > 
> 
> Do you mean that we should put these two checks after
> `exfat_put_dentry_set`, like below?
> 

Yes, that's what I mean.

> @@ -645,18 +645,6 @@ static int exfat_find(struct inode *dir, const struct qstr *qname,
>  	info->valid_size = le64_to_cpu(ep2->dentry.stream.valid_size);
>  	info->size = le64_to_cpu(ep2->dentry.stream.size);
>  
> -	if (info->valid_size < 0) {
> -		exfat_fs_error(sb, "data valid size is invalid(%lld)", info->valid_size);
> -		return -EIO;
> -	}
> -
> -	if (unlikely(EXFAT_B_TO_CLU_ROUND_UP(info->size, sbi) > sbi->used_clusters)) {
> -		exfat_fs_error(sb, "data size is invalid(%lld)", info->size);
> -		return -EIO;
> -	}
> -
>  	info->start_clu = le32_to_cpu(ep2->dentry.stream.start_clu);
>  	if (!is_valid_cluster(sbi, info->start_clu) && info->size) {
>  		exfat_warn(sb, "start_clu is invalid cluster(0x%x)",
> @@ -694,6 +682,16 @@ static int exfat_find(struct inode *dir, const struct qstr *qname,
>  			     0);
>  	exfat_put_dentry_set(&es, false);
>  
> +	if (info->valid_size < 0) {
> +		exfat_fs_error(sb, "data valid size is invalid(%lld)", info->valid_size);
> +		return -EIO;
> +	}
> +
> +	if (unlikely(EXFAT_B_TO_CLU_ROUND_UP(info->size, sbi) > sbi->used_clusters)) {
> +		exfat_fs_error(sb, "data size is invalid(%lld)", info->size);
> +		return -EIO;
> +	}
> +
>  	if (ei->start_clu == EXFAT_FREE_CLUSTER) {
>  		exfat_fs_error(sb,
>  			       "non-zero size file starts with zero cluster (size : %llu, p_dir : %u, entry : 0x%08x)",
> 
> > > --
> > > 2.39.5 (Apple Git-154)
>