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

[Samuel Thibault]

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.

This is CVE-2017-11434.

Reported-by: Reno Robert <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
Signed-off-by: Samuel Thibault <address@hidden>
---
 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