linux-kernel - Re: [PATCH 1/2] proc: fix to check name length in proc_lookup

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Date:   Wed, 1 Feb 2023 21:01:14 +0800
From:   Chao Yu <chao@...nel.org>
To:     akpm@...ux-foundation.org
Cc:     viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, adobriyan@...il.com
Subject: Re: [PATCH 1/2] proc: fix to check name length in proc_lookup_de()

Hi Andrew,

Could you please take a look at this patchset? Or should I ping
Alexey Dobriyan?

Thanks,

On 2023/1/31 23:55, 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.
> 
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>   fs/proc/generic.c  | 5 ++++-
>   fs/proc/internal.h | 3 +++
>   2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index 878d7c6db919..f547e9593a77 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -245,6 +245,9 @@ 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);
> +
>   	read_lock(&proc_subdir_lock);
>   	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
>   	if (de) {
> @@ -401,7 +404,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
>   		goto out;
>   	qstr.name = fn;
>   	qstr.len = strlen(fn);
> -	if (qstr.len == 0 || qstr.len >= 256) {
> +	if (qstr.len == 0 || qstr.len > PROC_NAME_LEN) {
>   		WARN(1, "name len %u\n", qstr.len);
>   		return NULL;
>   	}
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index b701d0207edf..7611bc684d9e 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -142,6 +142,9 @@ unsigned name_to_int(const struct qstr *qstr);
>   /* Worst case buffer size needed for holding an integer. */
>   #define PROC_NUMBUF 13
>   
> +/* Max name length of procfs dirent */
> +#define PROC_NAME_LEN		255
> +
>   /*
>    * array.c
>    */