linux-kernel - Re: [PATCH v2] exfat: fix refcount leak in exfat

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Message-ID:
 <PUZPR04MB63160FD802F4A0D9050EF49981F3A@PUZPR04MB6316.apcprd04.prod.outlook.com>
Date: Wed, 22 Oct 2025 04:55:02 +0000
From: "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To: Shuhao Fu <sfual@....ust.hk>, Namjae Jeon <linkinjeon@...nel.org>,
        Sungjong Seo <sj1557.seo@...sung.com>
CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] exfat: fix refcount leak in exfat_find

On Tue, Oct 21, 2025 16:42 Shuhao Fu <sfual@....ust.hk> wrote:
> Fix refcount leaks in `exfat_find` related to `exfat_get_dentry_set`.
> 
> Function `exfat_get_dentry_set` would increase the reference counter of
> `es->bh` on success. Therefore, `exfat_put_dentry_set` must be called
> after `exfat_get_dentry_set` to ensure refcount consistency. This patch
> relocate two checks to avoid possible leaks.
> 
> Fixes: 82ebecdc74ff ("exfat: fix improper check of dentry.stream.valid_size")
> Fixes: 13940cef9549 ("exfat: add a check for invalid data size")
> Signed-off-by: Shuhao Fu <sfual@....ust.hk>
> ---
> Change to v1: [1]
> - relocate two checks
> 
> [1] https://lore.kernel.org/linux-fsdevel/aPZOpRfVPZCP8vPw@chcpu18/
> ---
>  fs/exfat/namei.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
> index 745dce29d..dfe957493 100644
> --- a/fs/exfat/namei.c
> +++ b/fs/exfat/namei.c
> @@ -645,16 +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)",
> @@ -692,6 +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)",

Looks good to me.
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@...y.com>

> --
> 2.39.5 (Apple Git-154)