slirp: check len against dhcp options array endv2.10.0-rc4v2.10.0-rc3v2.10.0-rc2v2.10.0

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.

This is CVE-2017-11434.

Reported-by: Reno Robert <renorobert@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/bootp.c b/bootp.c
index baa6380..810da0c 100644
--- a/bootp.c
+++ b/bootp.c
@@ -129,6 +129,9 @@ 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) {