linux-kernel - Re: [PATCH v2] fs: ocfs2: Replace strlcpy with sysfs

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Date:   Wed, 13 Sep 2023 11:47:39 +0800
From:   Joseph Qi <joseph.qi@...ux.alibaba.com>
To:     Azeem Shaikh <azeemshaikh38@...il.com>,
        akpm <akpm@...ux-foundation.org>
Cc:     linux-hardening@...r.kernel.org, ocfs2-devel@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Christian Brauner <brauner@...nel.org>,
        Dave Chinner <dchinner@...hat.com>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2] fs: ocfs2: Replace strlcpy with sysfs_emit



On 9/1/23 3:38 AM, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with sysfs_emit().
> 
> Direct replacement is safe here since its ok for `kernel_param_ops.get()`
> to return -errno [3].
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> [3] https://elixir.bootlin.com/linux/v6.5/source/include/linux/moduleparam.h#L52
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>

Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>

> ---
> v2:
>  * Removes patch [1/2] which replaced module_param_call with module_param_cb.
>  * Use sysfs_emit instead of strscpy.
> 
> v1:
>  * https://lore.kernel.org/all/20230830215426.4181755-1-azeemshaikh38@gmail.com/
> 
>  fs/ocfs2/dlmfs/dlmfs.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
> index 81265123ce6c..b38776ba3306 100644
> --- a/fs/ocfs2/dlmfs/dlmfs.c
> +++ b/fs/ocfs2/dlmfs/dlmfs.c
> @@ -80,8 +80,7 @@ static int param_set_dlmfs_capabilities(const char *val,
>  static int param_get_dlmfs_capabilities(char *buffer,
>  					const struct kernel_param *kp)
>  {
> -	return strlcpy(buffer, DLMFS_CAPABILITIES,
> -		       strlen(DLMFS_CAPABILITIES) + 1);
> +	return sysfs_emit(buffer, DLMFS_CAPABILITIES);
>  }
>  module_param_call(capabilities, param_set_dlmfs_capabilities,
>  		  param_get_dlmfs_capabilities, NULL, 0444);
> --
> 2.42.0.283.g2d96d420d3-goog
>