From: Herbert Xu <herbert@gondor.apana.org.au>
To: syzbot <syzbot+e4c1dd36fc6b98c50859@syzkaller.appspotmail.com>
Cc: davem@davemloft.net, kuba@kernel.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
steffen.klassert@secunet.com, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] UBSAN: shift-out-of-bounds in xfrm_selector_match
Date: Tue, 15 Jun 2021 13:31:59 +0800 [thread overview]
Message-ID: <20210615053159.GA5412@gondor.apana.org.au> (raw)
In-Reply-To: <000000000000008a6c05c46e45a4@google.com>
On Thu, Jun 10, 2021 at 12:19:26PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 13c62f53 net/sched: act_ct: handle DNAT tuple collision
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=16635470300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=770708ea7cfd4916
> dashboard link: https://syzkaller.appspot.com/bug?extid=e4c1dd36fc6b98c50859
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e4c1dd36fc6b98c50859@syzkaller.appspotmail.com
>
> UBSAN: shift-out-of-bounds in ./include/net/xfrm.h:838:23
> shift exponent -64 is negative
> CPU: 0 PID: 12625 Comm: syz-executor.1 Not tainted 5.13.0-rc3-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:79 [inline]
> dump_stack+0x141/0x1d7 lib/dump_stack.c:120
> ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
> __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:327
> addr4_match include/net/xfrm.h:838 [inline]
> __xfrm4_selector_match net/xfrm/xfrm_policy.c:201 [inline]
> xfrm_selector_match.cold+0x35/0x3a net/xfrm/xfrm_policy.c:227
> xfrm_state_look_at+0x16d/0x440 net/xfrm/xfrm_state.c:1022
This appears to be an xfrm_state object with an IPv4 selector
that somehow has a prefixlen (d or s) of 96.
AFAICS this is not possible through xfrm_user. OTOH it is not
obvious that af_key is entirely consistent in how it verifies
the prefix length, in particular, it seems to be possible for
two addresses with conflicting families to be provided as src/dst.
Can you confirm that this is indeed using af_key (a quick read
of the syzbot log seems to indicate that this is the case)?
Thanks,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2021-06-15 5:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 19:19 [syzbot] UBSAN: shift-out-of-bounds in xfrm_selector_match syzbot
2021-06-15 5:31 ` Herbert Xu [this message]
2021-06-15 5:51 ` Dmitry Vyukov
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