linux-kernel - [PATCH 4.19 02/20] net: ipv6: fix skb_over_panic in __ip6_append

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220325150417.082295724@linuxfoundation.org>
Date:   Fri, 25 Mar 2022 16:04:40 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+e223cf47ec8ae183f2a0@...kaller.appspotmail.com,
        Tadeusz Struk <tadeusz.struk@...aro.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 4.19 02/20] net: ipv6: fix skb_over_panic in __ip6_append_data

From: Tadeusz Struk <tadeusz.struk@...aro.org>

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:<NULL>

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@...kaller.appspotmail.com
Signed-off-by: Tadeusz Struk <tadeusz.struk@...aro.org>
Acked-by: Willem de Bruijn <willemb@...gle.com>
Link: https://lore.kernel.org/r/20220310232538.1044947-1-tadeusz.struk@linaro.org
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/ip6_output.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1325,8 +1325,8 @@ static int __ip6_append_data(struct sock
 		      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 -