Commit a6f6bb6b authored by Eric Dumazet's avatar Eric Dumazet Committed by Ben Hutchings

ipv6: fix ip6_tnl_parse_tlv_enc_lim()

[ Upstream commit fbfa743a ]

This function suffers from multiple issues.

First one is that pskb_may_pull() may reallocate skb->head,
so the 'raw' pointer needs either to be reloaded or not used at all.

Second issue is that NEXTHDR_DEST handling does not validate
that the options are present in skb->data, so we might read
garbage or access non existent memory.

With help from Willem de Bruijn.
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarDmitry Vyukov  <dvyukov@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 47c192ef
...@@ -372,18 +372,19 @@ ip6_tnl_dev_uninit(struct net_device *dev) ...@@ -372,18 +372,19 @@ ip6_tnl_dev_uninit(struct net_device *dev)
static __u16 static __u16
parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw) parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw)
{ {
const struct ipv6hdr *ipv6h = (const struct ipv6hdr *) raw; const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)raw;
__u8 nexthdr = ipv6h->nexthdr; unsigned int nhoff = raw - skb->data;
__u16 off = sizeof (*ipv6h); unsigned int off = nhoff + sizeof(*ipv6h);
u8 next, nexthdr = ipv6h->nexthdr;
while (ipv6_ext_hdr(nexthdr) && nexthdr != NEXTHDR_NONE) { while (ipv6_ext_hdr(nexthdr) && nexthdr != NEXTHDR_NONE) {
__u16 optlen = 0;
struct ipv6_opt_hdr *hdr; struct ipv6_opt_hdr *hdr;
if (raw + off + sizeof (*hdr) > skb->data && u16 optlen;
!pskb_may_pull(skb, raw - skb->data + off + sizeof (*hdr)))
if (!pskb_may_pull(skb, off + sizeof(*hdr)))
break; break;
hdr = (struct ipv6_opt_hdr *) (raw + off); hdr = (struct ipv6_opt_hdr *)(skb->data + off);
if (nexthdr == NEXTHDR_FRAGMENT) { if (nexthdr == NEXTHDR_FRAGMENT) {
struct frag_hdr *frag_hdr = (struct frag_hdr *) hdr; struct frag_hdr *frag_hdr = (struct frag_hdr *) hdr;
if (frag_hdr->frag_off) if (frag_hdr->frag_off)
...@@ -394,20 +395,29 @@ parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw) ...@@ -394,20 +395,29 @@ parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw)
} else { } else {
optlen = ipv6_optlen(hdr); optlen = ipv6_optlen(hdr);
} }
/* cache hdr->nexthdr, since pskb_may_pull() might
* invalidate hdr
*/
next = hdr->nexthdr;
if (nexthdr == NEXTHDR_DEST) { if (nexthdr == NEXTHDR_DEST) {
__u16 i = off + 2; u16 i = 2;
/* Remember : hdr is no longer valid at this point. */
if (!pskb_may_pull(skb, off + optlen))
break;
while (1) { while (1) {
struct ipv6_tlv_tnl_enc_lim *tel; struct ipv6_tlv_tnl_enc_lim *tel;
/* No more room for encapsulation limit */ /* No more room for encapsulation limit */
if (i + sizeof (*tel) > off + optlen) if (i + sizeof(*tel) > optlen)
break; break;
tel = (struct ipv6_tlv_tnl_enc_lim *) &raw[i]; tel = (struct ipv6_tlv_tnl_enc_lim *) skb->data + off + i;
/* return index of option if found and valid */ /* return index of option if found and valid */
if (tel->type == IPV6_TLV_TNL_ENCAP_LIMIT && if (tel->type == IPV6_TLV_TNL_ENCAP_LIMIT &&
tel->length == 1) tel->length == 1)
return i; return i + off - nhoff;
/* else jump to next option */ /* else jump to next option */
if (tel->type) if (tel->type)
i += tel->length + 2; i += tel->length + 2;
...@@ -415,7 +425,7 @@ parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw) ...@@ -415,7 +425,7 @@ parse_tlv_tnl_enc_lim(struct sk_buff *skb, __u8 * raw)
i++; i++;
} }
} }
nexthdr = hdr->nexthdr; nexthdr = next;
off += optlen; off += optlen;
} }
return 0; return 0;
......
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