linux-kernel - RE: [PATCH v1] exfat: fix unexpected EOF while reading dir

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Date:   Thu, 29 Dec 2022 11:25:58 +0900
From:   "Sungjong Seo" <sj1557.seo@...sung.com>
To:     <linkinjeon@...nel.org>
Cc:     <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "'Wang Yugui'" <wangyugui@...-tech.com>
Subject: RE: [PATCH v1] exfat: fix unexpected EOF while reading dir

> If the position is not aligned with the dentry size, the return
> value of readdir() will be NULL and errno is 0, which means the
> end of the directory stream is reached.
> 
> If the position is aligned with dentry size, but there is no file
> or directory at the position, exfat_readdir() will continue to
> get dentry from the next dentry. So the dentry gotten by readdir()
> may not be at the position.
> 
> After this commit, if the position is not aligned with the dentry
> size, round the position up to the dentry size and continue to get
> the dentry.
> 
> Fixes: ca06197382bd ("exfat: add directory operations")
> 
> Signed-off-by: Yuezhang Mo <Yuezhang.Mo@...y.com>
> Reviewed-by: Andy Wu <Andy.Wu@...y.com>
> Reviewed-by: Aoyama Wataru <wataru.aoyama@...y.com>
> Reported-by: Wang Yugui <wangyugui@...-tech.com>

Looks good. Thanks.

Reviewed-by: Sungjong Seo <sj1557.seo@...sung.com>

> ---
>  fs/exfat/dir.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
> index 1dfa67f307f1..1122bee3b634 100644
> --- a/fs/exfat/dir.c
> +++ b/fs/exfat/dir.c
> @@ -234,10 +234,7 @@ static int exfat_iterate(struct file *file, struct
> dir_context *ctx)
>  		fake_offset = 1;
>  	}
> 
> -	if (cpos & (DENTRY_SIZE - 1)) {
> -		err = -ENOENT;
> -		goto unlock;
> -	}
> +	cpos = round_up(cpos, DENTRY_SIZE);
> 
>  	/* name buffer should be allocated before use */
>  	err = exfat_alloc_namebuf(nb);
> --
> 2.25.1