| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.12 069/106] ipv6: avoid overflow of offset in ip6_find_1stfragopt | Date | Wed, 9 Aug 2017 09:52:53 -0700 |
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4.12-stable review patch. If anyone has any objections, please let me know.
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From: Sabrina Dubroca <sd@queasysnail.net>
[ Upstream commit 6399f1fae4ec29fab5ec76070435555e256ca3a6 ]
In some cases, offset can overflow and can cause an infinite loop in ip6_find_1stfragopt(). Make it unsigned int to prevent the overflow, and cap it at IPV6_MAXPLEN, since packets larger than that should be invalid.
This problem has been here since before the beginning of git history.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv6/output_core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/net/ipv6/output_core.c +++ b/net/ipv6/output_core.c @@ -78,7 +78,7 @@ EXPORT_SYMBOL(ipv6_select_ident); int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr) { - u16 offset = sizeof(struct ipv6hdr); + unsigned int offset = sizeof(struct ipv6hdr); unsigned int packet_len = skb_tail_pointer(skb) - skb_network_header(skb); int found_rhdr = 0; @@ -86,6 +86,7 @@ int ip6_find_1stfragopt(struct sk_buff * while (offset <= packet_len) { struct ipv6_opt_hdr *exthdr; + unsigned int len; switch (**nexthdr) { @@ -111,7 +112,10 @@ int ip6_find_1stfragopt(struct sk_buff * exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) + offset); - offset += ipv6_optlen(exthdr); + len = ipv6_optlen(exthdr); + if (len + offset >= IPV6_MAXPLEN) + return -EINVAL; + offset += len; *nexthdr = &exthdr->nexthdr; }
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