From 6c870ac3f45ef118a5c3318a4b0f3903d2f2e020 Mon Sep 17 00:00:00 2001 From: Tadeusz Struk Date: Tue, 28 Jun 2022 11:36:16 +0800 Subject: [PATCH] net: ipv6: fix skb_over_panic in __ip6_append_data stable inclusion from stable-v5.10.109 commit ae8ec5eabb1a0e672e054ef50374f3d8508d6828 bugzilla: https://gitee.com/openeuler/kernel/issues/I574AE Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae8ec5eabb1a0e672e054ef50374f3d8508d6828 -------------------------------- commit 5e34af4142ffe68f01c8a9acae83300f8911e20c upstream. 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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yu Liao Reviewed-by: Wei Li Signed-off-by: Zheng Zengkai --- net/ipv6/ip6_output.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index d6f2126f4618..2aa39ce7093d 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1500,8 +1500,8 @@ 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 - -- GitLab