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Tsirkin" To: P J P Subject: Re: [PATCH v2 2/2] pci: ensure configuration access is within bounds Message-ID: <20200604053733-mutt-send-email-mst@kernel.org> References: <20200603202251.1199170-1-ppandit@redhat.com> <20200603202251.1199170-3-ppandit@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200603202251.1199170-3-ppandit@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/04 01:14:08 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: Daniel P =?iso-8859-1?Q?=2E_Berrang=E9?= , Prasad J Pandit , Yi Ren , QEMU Developers , Gerd Hoffmann , Ren Ding , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Hanqing Zhao Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jun 04, 2020 at 01:52:51AM +0530, P J P wrote: > From: Prasad J Pandit > > While reading PCI configuration bytes, a guest may send an > address towards the end of the configuration space. It may lead > to an OOB access issue. Assert that 'address + len' is within > PCI configuration space. > > Suggested-by: Philippe Mathieu-Daudé > Signed-off-by: Prasad J Pandit My understanding is that this can't really happen normally, this is more an assert in case some pci host devices are buggy, as is the case of alt-vga. Right? Pls clarify commit log so it's obvious this is defence in depth. > --- > hw/pci/pci.c | 2 ++ > 1 file changed, 2 insertions(+) > > Update v2: assert PCI configuration access is within bounds > -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00711.html > > diff --git a/hw/pci/pci.c b/hw/pci/pci.c > index 70c66965f5..173bec4fd5 100644 > --- a/hw/pci/pci.c > +++ b/hw/pci/pci.c > @@ -1381,6 +1381,8 @@ uint32_t pci_default_read_config(PCIDevice *d, > { > uint32_t val = 0; > > + assert(address + len <= pci_config_size(d)); > + > if (pci_is_express_downstream_port(d) && > ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) { > pcie_sync_bridge_lnk(d); > -- > 2.26.2