linux-kernel - Re: [PATCH V2] Fix unsafe memory access by memcmp

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Date:   Mon, 4 Apr 2022 19:33:01 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Charlie Sands <sandsch@...thvilleschools.net>,
        gregkh@...uxfoundation.org
Cc:     Larry.Finger@...inger.net, phil@...lpotter.co.uk,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] Fix unsafe memory access by memcmp

Hi Charlie,

On 4/4/22 05:52, Charlie Sands wrote:
> This patch fixes sparse warnings about the memcmp function unsafely
> accessing userspace memory without first copying it to kernel space.
> 
> Signed-off-by: Charlie Sands <sandsch@...thvilleschools.net>
> ---
> 
> V2: Fixed checkpatch.pl warning and changed variable name as suggested
> by Greg K. H. and improved error checking on the "copy_from_user" function as
> suggested by Pavel Skripkin.
> 

You did not improved error handling of copy_from_user() as I suggested. 
if (expr) and if (expr != 0) are exactly the same

>   drivers/staging/r8188eu/os_dep/ioctl_linux.c | 21 ++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/r8188eu/os_dep/ioctl_linux.c b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> index 7df213856d66..4b4eec2bde96 100644
> --- a/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> +++ b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> @@ -3233,23 +3233,28 @@ static int rtw_p2p_get(struct net_device *dev,
>   			       struct iw_request_info *info,
>   			       union iwreq_data *wrqu, char *extra)
>   {
> -	if (!memcmp(wrqu->data.pointer, "status", 6)) {
> +	char wrqu_data[9];
> +
> +	if (copy_from_user(wrqu_data, wrqu->data.pointer, 9) != 0)
> +		return 0;
> +

I've suggested to return -EFAULT here




With regards,
Pavel Skripkin

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