4.4-stable review patch. If anyone has any objections, please let me know.
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From: Stefan Nuernberger snu@amazon.com
commit 076ed3da0c9b2f88d9157dbe7044a45641ae369e upstream.
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 snu@amazon.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: Simon Veith sveith@amazon.de Cc: stable@vger.kernel.org Acked-by: Paul Moore paul@paul-moore.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv4/cipso_ipv4.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
--- a/net/ipv4/cipso_ipv4.c +++ b/net/ipv4/cipso_ipv4.c @@ -1582,7 +1582,7 @@ static int cipso_v4_parsetag_loc(const s * * 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) @@ -1592,10 +1592,8 @@ unsigned char *cipso_v4_optptr(const str 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: - return optptr; case IPOPT_END: return NULL; case IPOPT_NOOP: @@ -1604,6 +1602,11 @@ unsigned char *cipso_v4_optptr(const str default: taglen = optptr[1]; } + if (!taglen || taglen > optlen) + return NULL; + if (optptr[0] == IPOPT_CIPSO) + return optptr; + optlen -= taglen; optptr += taglen; }