Re: KASAN: use-after-free Read in bitmap_port_ext_cleanup

["Kadlecsik József" <kadlec@blackhole.kfki.hu>]

Hi,

On Fri, 10 Jan 2020, Cong Wang wrote:

> On Fri, Jan 10, 2020 at 10:44 AM syzbot
> <syzbot+4c3cc6dbe7259dbf9054@syzkaller.appspotmail.com> wrote:
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    b07f636f Merge tag 'tpmdd-next-20200108' of git://git.infr..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16c03259e00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=18698c0c240ba616
> > dashboard link: https://syzkaller.appspot.com/bug?extid=4c3cc6dbe7259dbf9054
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > userspace arch: i386
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10c365c6e00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=117df9e1e00000
> >
> > The bug was bisected to:
> >
> > commit b9a1e627405d68d475a3c1f35e685ccfb5bbe668
> > Author: Cong Wang <xiyou.wangcong@gmail.com>
> > Date:   Thu Jul 4 00:21:13 2019 +0000
> >
> >      hsr: implement dellink to clean up resources
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=118759e1e00000
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=138759e1e00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=158759e1e00000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+4c3cc6dbe7259dbf9054@syzkaller.appspotmail.com
> > Fixes: b9a1e627405d ("hsr: implement dellink to clean up resources")
> >
> > ==================================================================
> > BUG: KASAN: use-after-free in test_bit
> > include/asm-generic/bitops/instrumented-non-atomic.h:110 [inline]
> > BUG: KASAN: use-after-free in bitmap_port_ext_cleanup+0xe6/0x2a0
> > net/netfilter/ipset/ip_set_bitmap_gen.h:51
> > Read of size 8 at addr ffff8880a87a47c0 by task syz-executor559/9563
> >
> > CPU: 0 PID: 9563 Comm: syz-executor559 Not tainted 5.5.0-rc5-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0x197/0x210 lib/dump_stack.c:118
> >   print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
> >   __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
> >   kasan_report+0x12/0x20 mm/kasan/common.c:639
> >   check_memory_region_inline mm/kasan/generic.c:185 [inline]
> >   check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
> >   __kasan_check_read+0x11/0x20 mm/kasan/common.c:95
> >   test_bit include/asm-generic/bitops/instrumented-non-atomic.h:110 [inline]
> >   bitmap_port_ext_cleanup+0xe6/0x2a0
> 
> map->members is freed by ip_set_free() right before using it in
> mtype_ext_cleanup() again. So I think probably we just have to
> move it down:

Yes, exactly. As you suggested, could you submit a patch?

Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>

Best regards,
Jozsef
 
> diff --git a/net/netfilter/ipset/ip_set_bitmap_gen.h
> b/net/netfilter/ipset/ip_set_bitmap_gen.h
> index 1abd6f0dc227..077a2cb65fcb 100644
> --- a/net/netfilter/ipset/ip_set_bitmap_gen.h
> +++ b/net/netfilter/ipset/ip_set_bitmap_gen.h
> @@ -60,9 +60,9 @@ mtype_destroy(struct ip_set *set)
>         if (SET_WITH_TIMEOUT(set))
>                 del_timer_sync(&map->gc);
> 
> -       ip_set_free(map->members);
>         if (set->dsize && set->extensions & IPSET_EXT_DESTROY)
>                 mtype_ext_cleanup(set);
> +       ip_set_free(map->members);
>         ip_set_free(map);
> 
>         set->data = NULL;
> 
> Thanks.
> 

-
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