From 5e34af4142ffe68f01c8a9acae83300f8911e20c Mon Sep 17 00:00:00 2001 From: Tadeusz Struk Date: Thu, 10 Mar 2022 15:25:38 -0800 Subject: net: ipv6: fix skb_over_panic in __ip6_append_data Syzbot found a kernel bug in the ipv6 stack: LINK: https://syzkaller.appspot.com/bug?id=205d6f11d72329ab8d62a610c44c5e7e25415580 The reproducer triggers it by sending a crafted message via sendmmsg() call, which triggers skb_over_panic, and crashes the kernel: skbuff: skb_over_panic: text:ffffffff84647fb4 len:65575 put:65575 head:ffff888109ff0000 data:ffff888109ff0088 tail:0x100af end:0xfec0 dev: Update the check that prevents an invalid packet with MTU equal to the fregment header size to eat up all the space for payload. The reproducer can be found here: LINK: https://syzkaller.appspot.com/text?tag=ReproC&x=1648c83fb00000 Reported-by: syzbot+e223cf47ec8ae183f2a0@syzkaller.appspotmail.com Signed-off-by: Tadeusz Struk Acked-by: Willem de Bruijn Link: https://lore.kernel.org/r/20220310232538.1044947-1-tadeusz.struk@linaro.org Signed-off-by: Jakub Kicinski --- net/ipv6/ip6_output.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv6') diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 4788f6b37053..194832663d85 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1476,8 +1476,8 @@ static int __ip6_append_data(struct sock *sk, sizeof(struct frag_hdr) : 0) + rt->rt6i_nfheader_len; - if (mtu < fragheaderlen || - ((mtu - fragheaderlen) & ~7) + fragheaderlen < sizeof(struct frag_hdr)) + if (mtu <= fragheaderlen || + ((mtu - fragheaderlen) & ~7) + fragheaderlen <= sizeof(struct frag_hdr)) goto emsgsize; maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen - -- cgit v1.2.3 From 4db4075f92af2b28f415fc979ab626e6b37d67b6 Mon Sep 17 00:00:00 2001 From: Sabrina Dubroca Date: Thu, 10 Mar 2022 11:49:00 +0100 Subject: esp6: fix check on ipv6_skip_exthdr's return value Commit 5f9c55c8066b ("ipv6: check return value of ipv6_skip_exthdr") introduced an incorrect check, which leads to all ESP packets over either TCPv6 or UDPv6 encapsulation being dropped. In this particular case, offset is negative, since skb->data points to the ESP header in the following chain of headers, while skb->network_header points to the IPv6 header: IPv6 | ext | ... | ext | UDP | ESP | ... That doesn't seem to be a problem, especially considering that if we reach esp6_input_done2, we're guaranteed to have a full set of headers available (otherwise the packet would have been dropped earlier in the stack). However, it means that the return value will (intentionally) be negative. We can make the test more specific, as the expected return value of ipv6_skip_exthdr will be the (negated) size of either a UDP header, or a TCP header with possible options. In the future, we should probably either make ipv6_skip_exthdr explicitly accept negative offsets (and adjust its return value for error cases), or make ipv6_skip_exthdr only take non-negative offsets (and audit all callers). Fixes: 5f9c55c8066b ("ipv6: check return value of ipv6_skip_exthdr") Reported-by: Xiumei Mu Signed-off-by: Sabrina Dubroca Signed-off-by: Steffen Klassert --- net/ipv6/esp6.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'net/ipv6') diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c index b0ffbcd5432d..55d604c9b3b3 100644 --- a/net/ipv6/esp6.c +++ b/net/ipv6/esp6.c @@ -812,8 +812,7 @@ int esp6_input_done2(struct sk_buff *skb, int err) struct tcphdr *th; offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off); - - if (offset < 0) { + if (offset == -1) { err = -EINVAL; goto out; } -- cgit v1.2.3