Re: [PATCH 07/13] media: s5p-jpeg: prevent buffer overflows

[Jacek Anaszewski <jacek.anaszewski@gmail.com>]

Hi Mauro,

On 10/16/24 12:22, Mauro Carvalho Chehab wrote:
> The current logic allows word to be less than 2. If this happens,
> there will be buffer overflows. Add extra checks to prevent it.
> 
> While here, remove an unused word = 0 assignment.
> 
> Fixes: 6c96dbbc2aa9 ("[media] s5p-jpeg: add support for 5433")
> Cc: stable@vger.kernel.org
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> ---
>   .../media/platform/samsung/s5p-jpeg/jpeg-core.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/platform/samsung/s5p-jpeg/jpeg-core.c b/drivers/media/platform/samsung/s5p-jpeg/jpeg-core.c
> index d2c4a0178b3c..1db4609b3557 100644
> --- a/drivers/media/platform/samsung/s5p-jpeg/jpeg-core.c
> +++ b/drivers/media/platform/samsung/s5p-jpeg/jpeg-core.c
> @@ -775,11 +775,14 @@ static void exynos4_jpeg_parse_decode_h_tbl(struct s5p_jpeg_ctx *ctx)
>   		(unsigned long)vb2_plane_vaddr(&vb->vb2_buf, 0) + ctx->out_q.sos + 2;
>   	jpeg_buffer.curr = 0;
>   
> -	word = 0;
> -
>   	if (get_word_be(&jpeg_buffer, &word))
>   		return;
> -	jpeg_buffer.size = (long)word - 2;
> +
> +	if (word < 2)
> +		jpeg_buffer.size = 0;
> +	else
> +		jpeg_buffer.size = (long)word - 2;
> +
>   	jpeg_buffer.data += 2;
>   	jpeg_buffer.curr = 0;
>   
> @@ -1058,6 +1061,7 @@ static int get_word_be(struct s5p_jpeg_buffer *buf, unsigned int *word)
>   	if (byte == -1)
>   		return -1;
>   	*word = (unsigned int)byte | temp;
> +
>   	return 0;
>   }
>   
> @@ -1145,7 +1149,7 @@ static bool s5p_jpeg_parse_hdr(struct s5p_jpeg_q_data *result,
>   			if (get_word_be(&jpeg_buffer, &word))
>   				break;
>   			length = (long)word - 2;
> -			if (!length)
> +			if (length <= 0)
>   				return false;
>   			sof = jpeg_buffer.curr; /* after 0xffc0 */
>   			sof_len = length;
> @@ -1176,7 +1180,7 @@ static bool s5p_jpeg_parse_hdr(struct s5p_jpeg_q_data *result,
>   			if (get_word_be(&jpeg_buffer, &word))
>   				break;
>   			length = (long)word - 2;
> -			if (!length)
> +			if (length <= 0)
>   				return false;
>   			if (n_dqt >= S5P_JPEG_MAX_MARKER)
>   				return false;
> @@ -1189,7 +1193,7 @@ static bool s5p_jpeg_parse_hdr(struct s5p_jpeg_q_data *result,
>   			if (get_word_be(&jpeg_buffer, &word))
>   				break;
>   			length = (long)word - 2;
> -			if (!length)
> +			if (length <= 0)
>   				return false;
>   			if (n_dht >= S5P_JPEG_MAX_MARKER)
>   				return false;
> @@ -1214,6 +1218,7 @@ static bool s5p_jpeg_parse_hdr(struct s5p_jpeg_q_data *result,
>   			if (get_word_be(&jpeg_buffer, &word))
>   				break;
>   			length = (long)word - 2;
> +			/* No need to check underflows as skip() does it  */
>   			skip(&jpeg_buffer, length);
>   			break;
>   		}

Seems reasonable.

Reviewed-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

-- 
Best regards,
Jacek Anaszewski