commit 40413955ee26 ("Cipso: cipso_v4_optptr enter infinite loop") fixed
a possible infinite loop in the IP option parsing of CIPSO. The fix
assumes that ip_options_compile filtered out all zero length options and
that no other one-byte options beside IPOPT_END and IPOPT_NOOP exist.
While this assumption currently holds true, add explicit checks for zero
length and invalid length options to be safe for the future. Even though
ip_options_compile should have validated the options, the introduction of
new one-byte options can still confuse this code without the additional
checks.
Signed-off-by: Stefan Nuernberger <s...@amazon.com>
Reviewed-by: David Woodhouse <d...@amazon.co.uk>
Reviewed-by: Simon Veith <sve...@amazon.de>
Cc: sta...@vger.kernel.org
---
net/ipv4/cipso_ipv4.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 82178cc69c96..f291b57b8474 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1512,7 +1512,7 @@ static int cipso_v4_parsetag_loc(const struct
cipso_v4_doi *doi_def,
*
* Description:
* Parse the packet's IP header looking for a CIPSO option. Returns a pointer
- * to the start of the CIPSO option on success, NULL if one if not found.
+ * to the start of the CIPSO option on success, NULL if one is not found.
*
*/
unsigned char *cipso_v4_optptr(const struct sk_buff *skb)
@@ -1522,9 +1522,11 @@ unsigned char *cipso_v4_optptr(const struct sk_buff *skb)
int optlen;
int taglen;
- for (optlen = iph->ihl*4 - sizeof(struct iphdr); optlen > 0; ) {
+ for (optlen = iph->ihl*4 - sizeof(struct iphdr); optlen > 1; ) {
switch (optptr[0]) {
case IPOPT_CIPSO:
+ if (!optptr[1] || optptr[1] > optlen)
+ return NULL;
return optptr;
case IPOPT_END:
return NULL;
@@ -1534,6 +1536,10 @@ unsigned char *cipso_v4_optptr(const struct sk_buff *skb)
default:
taglen = optptr[1];
}
+
+ if (!taglen || taglen > optlen)
+ break;
+
optlen -= taglen;
optptr += taglen;
}
--
2.19.0
