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From: Alexander Aring <aahringo@redhat.com>
Date: Thu, 14 Dec 2023 22:01:11 -0500
Message-ID: <CAK-6q+jsZ13Cs9iuk_WjFeYFCEnnj-dJ9QYkWaw4fh6Gi=JtHA@mail.gmail.com>
Subject: Re: [PATCH RESEND] mac802154: Fix uninit-value access in ieee802154_hdr_push_sechdr
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Zhang Shurong <zhang_shurong@foxmail.com>, alex.aring@gmail.com, 
	stefan@datenfreihafen.org, davem@davemloft.net, edumazet@google.com, 
	kuba@kernel.org, pabeni@redhat.com, linux-wpan@vger.kernel.org, 
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org, 
	harperchen1110@gmail.com
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Hi,

On Mon, Dec 4, 2023 at 3:57=E2=80=AFAM Miquel Raynal <miquel.raynal@bootlin=
.com> wrote:
>
> Hi Zhang,
>
> zhang_shurong@foxmail.com wrote on Sat,  2 Dec 2023 22:58:52 +0800:
>
> > The syzkaller reported an issue:
>
> Subject should start with [PATCH wpan]
>
> >
> > BUG: KMSAN: uninit-value in ieee802154_hdr_push_sechdr net/ieee802154/h=
eader_ops.c:54 [inline]
> > BUG: KMSAN: uninit-value in ieee802154_hdr_push+0x971/0xb90 net/ieee802=
154/header_ops.c:108
> >  ieee802154_hdr_push_sechdr net/ieee802154/header_ops.c:54 [inline]
> >  ieee802154_hdr_push+0x971/0xb90 net/ieee802154/header_ops.c:108
> >  ieee802154_header_create+0x9c0/0xc00 net/mac802154/iface.c:396
> >  wpan_dev_hard_header include/net/cfg802154.h:494 [inline]
> >  dgram_sendmsg+0xd1d/0x1500 net/ieee802154/socket.c:677
> >  ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
> >  sock_sendmsg_nosec net/socket.c:725 [inline]
> >  sock_sendmsg net/socket.c:748 [inline]
> >  ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2494
> >  ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2548
> >  __sys_sendmsg+0x225/0x3c0 net/socket.c:2577
> >  __compat_sys_sendmsg net/compat.c:346 [inline]
> >  __do_compat_sys_sendmsg net/compat.c:353 [inline]
> >  __se_compat_sys_sendmsg net/compat.c:350 [inline]
> >
> > We found hdr->key_id_mode is uninitialized in mac802154_set_header_secu=
rity()
> > which indicates hdr.fc.security_enabled should be 0. However, it is set=
 to be cb->secen before.
> > Later, ieee802154_hdr_push_sechdr is invoked, causing KMSAN complains u=
ninit-value issue.
>
> I am not too deeply involved in the security header but for me it feels
> like your patch does the opposite of what's needed. We should maybe
> initialize hdr->key_id_mode based on the value in cb->secen, no? (maybe
> Alexander will have a better understanding than I have).

I can't help yet with a better answer why syzkaller reports it but it
will break things as we using skb->cb to pass additional parameters
through header_ops->create()... in this case it is some sockopts of
af802154, I guess.

side note: we should stop doing that with skb->cb and introduce some
802.15.4 specific header_ops callback structure and not depend on such
generic callback which does not fit here (and maybe somebody does a
wrapper around that and reuse skb->cb for their needs, etc.)

- Alex