linux-kernel - Re: [PATCH] proc: fix to check name length in proc_lookup

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Message-ID: <Y72oBFXX6DiEh2/p@p183>
Date:   Tue, 10 Jan 2023 21:01:40 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Chao Yu <chao@...nel.org>
Cc:     akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] proc: fix to check name length in proc_lookup_de()

On Tue, Jan 10, 2023 at 11:21:12PM +0800, Chao Yu wrote:
> __proc_create() has limited dirent's max name length with 255, let's
> add this limitation in proc_lookup_de(), so that it can return
> -ENAMETOOLONG correctly instead of -ENOENT when stating a file which
> has out-of-range name length.

Both returns are correct and this is trading one errno for another.

> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -246,6 +246,9 @@ struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
>  {
>  	struct inode *inode;
>  
> +	if (dentry->d_name.len > PROC_NAME_LEN)
> +		return ERR_PTR(-ENAMETOOLONG);