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Fri, 17 Jul 2020 03:13:07 +0000 (UTC) Subject: Re: [PATCH] net: check payload length limit for all frames To: Alexander Bulekov , Li Qiang References: <20200716192335.1212638-1-ppandit@redhat.com> <20200717012151.tlfmc6hsfia22f4e@mozz.bu.edu> From: Jason Wang Message-ID: <4e4909ae-db2f-4a32-ae5c-d52149e80a8c@redhat.com> Date: Fri, 17 Jul 2020 11:13:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200717012151.tlfmc6hsfia22f4e@mozz.bu.edu> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=jasowang@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/16 23:13:19 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Prasad J Pandit , Dmitry Fleytman , QEMU Developers , P J P Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/7/17 上午9:21, Alexander Bulekov wrote: > On 200717 0853, Li Qiang wrote: >> P J P 于2020年7月17日周五 上午3:26写道： >>> From: Prasad J Pandit >>> >>> While sending packets, the check that packet 'payload_len' >>> is within 64kB limit, seems to happen only for GSO frames. >>> It may lead to use-after-free or out-of-bounds access like >>> issues when sending non-GSO frames. Check the 'payload_len' >>> limit for all packets, irrespective of the gso type. >>> >> Hello Prasad, >> Which issue are you trying to solve, any reference linking? >> >> I also send a patch related this part and also a UAF. >> >> Thanks, >> Li Qiang > Hi Li, Prasad, > I reported a UAF privately to QEMU-Security in May. I believe the one Li > is referring to is this one https://bugs.launchpad.net/qemu/+bug/1886362 > > When I saw Prasad's email, I was worried that I reported the same bug > twice, but I can still reproduce LP#1886362 with Prasad's patch. > > On the other hand, I cannot reproduce either issue with Li's patch: > Message-Id: <20200716161453.61295-1-liq3ea@163.com> > > Based on this, I think there were two distinct issues. Both of the > crashes rely on e1000e tx loopback into e1000e MMIO. Since Li's > patch adds a TX bh, it seems to mitigate such types of issues. > > Sorry about any confusion. > -Alex Could you describe the issue you saw in details? (E.g the calltrace?) The commit log does not explain where we can get OOB or UAF. Thanks > >>> Reported-by: Alexander Bulekov >>> Signed-off-by: Prasad J Pandit >>> --- >>> hw/net/net_tx_pkt.c | 10 ++++------ >>> 1 file changed, 4 insertions(+), 6 deletions(-) >>> >>> diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c >>> index 162f802dd7..e66998a8f9 100644 >>> --- a/hw/net/net_tx_pkt.c >>> +++ b/hw/net/net_tx_pkt.c >>> @@ -607,12 +607,10 @@ bool net_tx_pkt_send(struct NetTxPkt *pkt, NetClientState *nc) >>> * Since underlying infrastructure does not support IP datagrams longer >>> * than 64K we should drop such packets and don't even try to send >>> */ >>> - if (VIRTIO_NET_HDR_GSO_NONE != pkt->virt_hdr.gso_type) { >>> - if (pkt->payload_len > >>> - ETH_MAX_IP_DGRAM_LEN - >>> - pkt->vec[NET_TX_PKT_L3HDR_FRAG].iov_len) { >>> - return false; >>> - } >>> + if (pkt->payload_len > >>> + ETH_MAX_IP_DGRAM_LEN - >>> + pkt->vec[NET_TX_PKT_L3HDR_FRAG].iov_len) { >>> + return false; >>> } >>> >>> if (pkt->has_virt_hdr || >>> -- >>> 2.26.2 >>> >>>