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[88.10.103.181]) by smtp.gmail.com with ESMTPSA id e15sm6025145wme.9.2020.06.03.23.07.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Jun 2020 23:07:54 -0700 (PDT) Subject: Re: [PATCH v2 2/2] pci: ensure configuration access is within bounds To: BALATON Zoltan , P J P References: <20200603202251.1199170-1-ppandit@redhat.com> <20200603202251.1199170-3-ppandit@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Autocrypt: addr=philmd@redhat.com; keydata= mQINBDXML8YBEADXCtUkDBKQvNsQA7sDpw6YLE/1tKHwm24A1au9Hfy/OFmkpzo+MD+dYc+7 bvnqWAeGweq2SDq8zbzFZ1gJBd6+e5v1a/UrTxvwBk51yEkadrpRbi+r2bDpTJwXc/uEtYAB GvsTZMtiQVA4kRID1KCdgLa3zztPLCj5H1VZhqZsiGvXa/nMIlhvacRXdbgllPPJ72cLUkXf z1Zu4AkEKpccZaJspmLWGSzGu6UTZ7UfVeR2Hcc2KI9oZB1qthmZ1+PZyGZ/Dy+z+zklC0xl XIpQPmnfy9+/1hj1LzJ+pe3HzEodtlVA+rdttSvA6nmHKIt8Ul6b/h1DFTmUT1lN1WbAGxmg CH1O26cz5nTrzdjoqC/b8PpZiT0kO5MKKgiu5S4PRIxW2+RA4H9nq7nztNZ1Y39bDpzwE5Sp bDHzd5owmLxMLZAINtCtQuRbSOcMjZlg4zohA9TQP9krGIk+qTR+H4CV22sWldSkVtsoTaA2 qNeSJhfHQY0TyQvFbqRsSNIe2gTDzzEQ8itsmdHHE/yzhcCVvlUzXhAT6pIN0OT+cdsTTfif MIcDboys92auTuJ7U+4jWF1+WUaJ8gDL69ThAsu7mGDBbm80P3vvUZ4fQM14NkxOnuGRrJxO qjWNJ2ZUxgyHAh5TCxMLKWZoL5hpnvx3dF3Ti9HW2dsUUWICSQARAQABtDJQaGlsaXBwZSBN YXRoaWV1LURhdWTDqSAoUGhpbCkgPHBoaWxtZEByZWRoYXQuY29tPokCVQQTAQgAPwIbDwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQSJweePYB7obIZ0lcuio/1u3q3A3gUCXsfWwAUJ KtymWgAKCRCio/1u3q3A3ircD/9Vjh3aFNJ3uF3hddeoFg1H038wZr/xi8/rX27M1Vj2j9VH 0B8Olp4KUQw/hyO6kUxqkoojmzRpmzvlpZ0cUiZJo2bQIWnvScyHxFCv33kHe+YEIqoJlaQc JfKYlbCoubz+02E2A6bFD9+BvCY0LBbEj5POwyKGiDMjHKCGuzSuDRbCn0Mz4kCa7nFMF5Jv piC+JemRdiBd6102ThqgIsyGEBXuf1sy0QIVyXgaqr9O2b/0VoXpQId7yY7OJuYYxs7kQoXI 6WzSMpmuXGkmfxOgbc/L6YbzB0JOriX0iRClxu4dEUg8Bs2pNnr6huY2Ft+qb41RzCJvvMyu gS32LfN0bTZ6Qm2A8ayMtUQgnwZDSO23OKgQWZVglGliY3ezHZ6lVwC24Vjkmq/2yBSLakZE 6DZUjZzCW1nvtRK05ebyK6tofRsx8xB8pL/kcBb9nCuh70aLR+5cmE41X4O+MVJbwfP5s/RW 9BFSL3qgXuXso/3XuWTQjJJGgKhB6xXjMmb1J4q/h5IuVV4juv1Fem9sfmyrh+Wi5V1IzKI7 RPJ3KVb937eBgSENk53P0gUorwzUcO+ASEo3Z1cBKkJSPigDbeEjVfXQMzNt0oDRzpQqH2vp apo2jHnidWt8BsckuWZpxcZ9+/9obQ55DyVQHGiTN39hkETy3Emdnz1JVHTU0Q== Message-ID: Date: Thu, 4 Jun 2020 08:07:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/04 01:08:38 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_H2=-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: =?UTF-8?Q?Daniel_P_=2e_Berrang=c3=a9?= , Prasad J Pandit , "Michael S . Tsirkin" , Yi Ren , QEMU Developers , Gerd Hoffmann , Ren Ding , Hanqing Zhao Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/4/20 12:13 AM, BALATON Zoltan wrote: > On Thu, 4 Jun 2020, 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 >> --- >> 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)); > > Does this allow guest now to crash QEMU? I think it was suggested that > assert should only be used for cases that can only arise from a > programming error and not from values set by the guest. If this is > considered to be an error now to call this function with wrong > parameters did you check other callers? I've found a few such as: > > hw/scsi/esp-pci.c > hw/watchdog/wdt_i6300esb.c > hw/ide/cmd646.c > hw/vfio/pci.c > > and maybe others. Would it be better to not crash just log invalid > access and either fix up parameters or return some garbage like 0? Yes, maybe I was not clear while reviewing v1, we need to audit the callers and fix them first, then we can safely add the assert here. > > Regards, > BALATON Zoltan > >> + >>     if (pci_is_express_downstream_port(d) && >>         ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, >> 2)) { >>         pcie_sync_bridge_lnk(d); >>