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

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Message-ID: <aPc-gzWVu6q9FmZ5@osx.local>
Date: Tue, 21 Oct 2025 16:04:49 +0800
From: Shuhao Fu <sfual@....ust.hk>
To: "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
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 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?

@@ -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)