linux-kernel - Re: KASAN: slab-out-of-bounds Read in bitmap_ip

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Date:   Fri, 31 Jan 2020 12:57:23 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Jozsef Kadlecsik <kadlec@...filter.org>
Cc:     coreteam@...filter.org, David Miller <davem@...emloft.net>,
        Marco Elver <elver@...gle.com>,
        Florian Westphal <fw@...len.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        jeremy@...zel.net, Kate Stewart <kstewart@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Netdev <netdev@...r.kernel.org>, netfilter-devel@...r.kernel.org,
        Pablo Neira Ayuso <pablo@...filter.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: KASAN: slab-out-of-bounds Read in bitmap_ip_add

On Sun, Jan 26, 2020 at 8:01 PM syzbot
<syzbot+f3e96783d74ee8ea9aa3@...kaller.appspotmail.com> wrote:
>
> syzbot has bisected this bug to:

Ok, the bisection is obviously bogus - it just points to where the
KASAN support was added to _notice_ the problem.

But is somebody looking at the actual KASAN report itself?

  https://syzkaller.appspot.com/bug?extid=f3e96783d74ee8ea9aa3

It does look like nfnetlink_rcv_msg() ends up looking at a bit:

 bitmap_ip_do_add net/netfilter/ipset/ip_set_bitmap_ip.c:83 [inline]
 bitmap_ip_add+0xef/0xe60 net/netfilter/ipset/ip_set_bitmap_gen.h:136
 bitmap_ip_uadt+0x73e/0xa10 net/netfilter/ipset/ip_set_bitmap_ip.c:186
 call_ad+0x1a0/0x5a0 net/netfilter/ipset/ip_set_core.c:1716
 ip_set_ad.isra.0+0x572/0xb20 net/netfilter/ipset/ip_set_core.c:1804
 ip_set_uadd+0x37/0x50 net/netfilter/ipset/ip_set_core.c:1829
 nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229

that is past the allocation:

 ip_set_alloc+0x38/0x5e net/netfilter/ipset/ip_set_core.c:255
 init_map_ip net/netfilter/ipset/ip_set_bitmap_ip.c:223 [inline]
 bitmap_ip_create+0x6ec/0xc20 net/netfilter/ipset/ip_set_bitmap_ip.c:327
 ip_set_create+0x6f1/0x1500 net/netfilter/ipset/ip_set_core.c:1111
 nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229

Maybe this has already been fixed, but I'm just trying to follow-up on
the syzbot report..

           Linus