From: Eric Dumazet <eric.dumazet@gmail.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Eric Biggers <ebiggers3@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
syzbot <syzbot+71d74a5406d02057d559@syzkaller.appspotmail.com>,
alexander.deucher@amd.com,
Andrey Konovalov <andreyknvl@google.com>,
Anoob Soman <anoob.soman@citrix.com>,
chris@chris-wilson.co.uk, David Miller <davem@davemloft.net>,
"Reshetova, Elena" <elena.reshetova@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kees Cook <keescook@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Mike Maloney <maloney@google.com>,
mchehab@kernel.org, netdev <netdev@vger.kernel.org>,
"Rosen, Rami" <rami.rosen@intel.com>,
Sowmini Varadhan <sowmini.varadhan@oracle.com>,
syzkaller-bugs@googlegroups.com,
Willem de Bruijn <willemb@google.com>
Subject: Re: KASAN: use-after-free Read in __dev_queue_xmit
Date: Wed, 9 May 2018 12:36:38 -0700 [thread overview]
Message-ID: <e7be4d14-be04-c40d-82ad-2050876f9ce9@gmail.com> (raw)
In-Reply-To: <CAF=yD-JPmU-q1iUoxtmyQa4BM=fU3CMR3BUDGNMg-4v8=2_deA@mail.gmail.com>
On 05/09/2018 12:21 PM, Willem de Bruijn wrote:
> Indeed. The skb shared info struct is zeroed by dev_validate_header
> as a result of dev->hard_header_len exceeding skb->end - skb->data.
>
> Not exactly sure yet how this can happen. The hard header length space
> is accounted for during allocation as reserved memory. But,
> packet_alloc_skb does call skb_reserve(), moving skb->data
> effectively beyond this reserved region.
>
> It may be incorrect to pass skb->data to dev_validate_header, as that
> does not point to the start of the ll_header anymore. Still figuring out what
> the right fix is..
>
I believe the bug happens if the sock_wmalloc() call at line 1921 has to sleep.
device can change (or at lest dev->hard_header_len can change)
So we need to bailout if reserved/hhlen had changed.
Or revert some patches, since dev_hold() and dev_put() are no longer high cost,
since it is now using per cpu counter.
next prev parent reply other threads:[~2018-05-09 19:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-04 4:58 KASAN: use-after-free Read in __dev_queue_xmit syzbot
2018-01-04 5:13 ` Eric Dumazet
2018-01-04 6:53 ` Eric Dumazet
2018-05-09 7:37 ` Eric Biggers
2018-05-09 16:11 ` Willem de Bruijn
2018-05-09 16:38 ` Willem de Bruijn
2018-05-09 19:21 ` Willem de Bruijn
2018-05-09 19:36 ` Eric Dumazet [this message]
2018-05-09 21:05 ` Willem de Bruijn
2018-05-10 21:49 ` Willem de Bruijn
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