Re: [Qemu-devel] [PULL 2/2] slirp: check len against dhcp options array end

[Samuel Thibault]

Samuel Thibault, on jeu. 03 août 2017 00:26:07 +0200, wrote:
> From: Prasad J Pandit <address@hidden>
> 
> While parsing dhcp options string in 'dhcp_decode', if an options'
> length 'len' appeared towards the end of 'bp_vend' array, ensuing
> read could lead to an OOB memory access issue. Add check to avoid it.
> 
> Reported-by: Reno Robert <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> Signed-off-by: Samuel Thibault <address@hidden>

Oops, this should have mentioned the CVE, I'll redo the pull request,
sorry.

> ---
>  slirp/bootp.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/slirp/bootp.c b/slirp/bootp.c
> index 5a4646c182..5dd1a415b5 100644
> --- a/slirp/bootp.c
> +++ b/slirp/bootp.c
> @@ -123,6 +123,9 @@ static void dhcp_decode(const struct bootp_t *bp, int 
> *pmsg_type,
>              if (p >= p_end)
>                  break;
>              len = *p++;
> +            if (p + len > p_end) {
> +                break;
> +            }
>              DPRINTF("dhcp: tag=%d len=%d\n", tag, len);
>  
>              switch(tag) {
> -- 
> 2.13.2
> 

-- 
Samuel
"...[Linux's] capacity to talk via any medium except smoke signals."
(By Dr. Greg Wettstein, Roger Maris Cancer Center)