linux-kernel - Re: [PATCH] drm/amdgpu: fix out of bounds write

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Message-ID: <20211027143945.GA1947580@roeck-us.net>
Date:   Wed, 27 Oct 2021 07:39:45 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Thelford Williams <tdwilliamsiv@...il.com>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH] drm/amdgpu: fix out of bounds write

On Wed, Oct 13, 2021 at 04:04:13PM -0400, Thelford Williams wrote:
> Size can be any value and is user controlled resulting in overwriting the
> 40 byte array wr_buf with an arbitrary length of data from buf.
> 
> Signed-off-by: Thelford Williams <tdwilliamsiv@...il.com>
> Signed-off-by: Alex Deucher <alexander.deucher@....com>

The fix works, but unless I am missing something it is incomplete.
parse_write_buffer_into_params() is called several times, and the
size parameter is always wrong. This patch only fixes one of several
instances of the problem.

Guenter

> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> index 814f67d86a3c..9b3ad56607bb 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> @@ -264,7 +264,7 @@ static ssize_t dp_link_settings_write(struct file *f, const char __user *buf,
>  	if (!wr_buf)
>  		return -ENOSPC;
>  
> -	if (parse_write_buffer_into_params(wr_buf, size,
> +	if (parse_write_buffer_into_params(wr_buf, wr_buf_size,
>  					   (long *)param, buf,
>  					   max_param_num,
>  					   &param_nums)) {
> -- 
> 2.33.0