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Date: Sun, 27 Dec 2020 22:11:35 +0800 From: Defang Bo <bodefang@....com> To: davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org, kuba@...nel.org Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Defang Bo <bodefang@....com> Subject: [PATCH] ipv6: Prevent overrun when parsing v6 header options Similar to commit<2423496af35>, the fragmentation code tries to parse the header options in order to figure out where to insert the fragment option. Since nexthdr points to an invalid option, the calculation of the size of the network header can made to be much larger than the linear section of the skb and data is read outside of it. Signed-off-by: Defang Bo <bodefang@....com> --- net/ipv6/mip6.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/net/ipv6/mip6.c b/net/ipv6/mip6.c index 878fcec..adf984c 100644 --- a/net/ipv6/mip6.c +++ b/net/ipv6/mip6.c @@ -251,8 +251,7 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, u8 **nexthdr) { u16 offset = sizeof(struct ipv6hdr); - struct ipv6_opt_hdr *exthdr = - (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1); + const unsigned char *nh = skb_network_header(skb); unsigned int packet_len = skb_tail_pointer(skb) - skb_network_header(skb); @@ -261,6 +260,7 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, *nexthdr = &ipv6_hdr(skb)->nexthdr; while (offset + 1 <= packet_len) { + struct ipv6_opt_hdr *exthdr; switch (**nexthdr) { case NEXTHDR_HOP: @@ -287,12 +287,15 @@ static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb, return offset; } + if (offset + sizeof(struct ipv6_opt_hdr) > packet_len) + return -EINVAL; + + exthdr = (struct ipv6_opt_hdr *)(nh + offset); offset += ipv6_optlen(exthdr); *nexthdr = &exthdr->nexthdr; - exthdr = (struct ipv6_opt_hdr *)(nh + offset); } - return offset; + return -EINVAL; } static int mip6_destopt_init_state(struct xfrm_state *x) @@ -387,8 +390,7 @@ static int mip6_rthdr_offset(struct xfrm_state *x, struct sk_buff *skb, u8 **nexthdr) { u16 offset = sizeof(struct ipv6hdr); - struct ipv6_opt_hdr *exthdr = - (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1); + const unsigned char *nh = skb_network_header(skb); unsigned int packet_len = skb_tail_pointer(skb) - skb_network_header(skb); @@ -396,7 +398,8 @@ static int mip6_rthdr_offset(struct xfrm_state *x, struct sk_buff *skb, *nexthdr = &ipv6_hdr(skb)->nexthdr; - while (offset + 1 <= packet_len) { + while (offset <= packet_len) { + struct ipv6_opt_hdr *exthdr; switch (**nexthdr) { case NEXTHDR_HOP: @@ -422,12 +425,15 @@ static int mip6_rthdr_offset(struct xfrm_state *x, struct sk_buff *skb, return offset; } + if (offset + sizeof(struct ipv6_opt_hdr) > packet_len) + return -EINVAL; + + exthdr = (struct ipv6_opt_hdr *)(nh + offset); offset += ipv6_optlen(exthdr); *nexthdr = &exthdr->nexthdr; - exthdr = (struct ipv6_opt_hdr *)(nh + offset); } - return offset; + return -EINVAL; } static int mip6_rthdr_init_state(struct xfrm_state *x) -- 2.7.4
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