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[2003:ea:8f1a:f00:f0f5:b870:7292:e828]) by smtp.googlemail.com with ESMTPSA id z7sm6469833wmi.33.2021.11.17.13.31.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Nov 2021 13:31:57 -0800 (PST) Message-ID: Date: Wed, 17 Nov 2021 22:31:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH v2] PCI/VPD: Add simple sanity check to pci_vpd_size() Content-Language: en-US From: Heiner Kallweit To: Bjorn Helgaas Cc: "linux-pci@vger.kernel.org" , =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= References: <223ffa56-7c2c-643a-d3a0-2175e85f6603@gmail.com> In-Reply-To: <223ffa56-7c2c-643a-d3a0-2175e85f6603@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 13.10.2021 20:37, Heiner Kallweit wrote: > We have a problem with a device where each VPD read returns 0x33 [0]. > This results in a valid VPD structure (except the tag id) and > therefore pci_vpd_size() scans the full VPD address range. > On an affected system this took ca. 80s. > > That's not acceptable, on the other hand we may not want to re-add > the old tag checks. In addition these tag check still wouldn't be able > to avoid the described scenario 100%. > Instead let's add a simple sanity check on the number of found tags. > A VPD image conforming to the PCI spec [1] can have max. 4 tags: > id string, ro section, rw section, end tag. > > [0] https://lore.kernel.org/lkml/20210915223218.GA1542966@bjorn-Precision-5520/ > [1] PCI 3.0 I.3.1. VPD Large and Small Resource Data Tags > > Reviewed-by: Krzysztof Wilczyński > Signed-off-by: Heiner Kallweit > --- > drivers/pci/vpd.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/pci/vpd.c b/drivers/pci/vpd.c > index a4fc4d069..921470611 100644 > --- a/drivers/pci/vpd.c > +++ b/drivers/pci/vpd.c > @@ -56,6 +56,7 @@ static size_t pci_vpd_size(struct pci_dev *dev) > { > size_t off = 0, size; > unsigned char tag, header[1+2]; /* 1 byte tag, 2 bytes length */ > + int num_tags = 0; > > while (pci_read_vpd_any(dev, off, 1, header) == 1) { > size = 0; > @@ -63,6 +64,10 @@ static size_t pci_vpd_size(struct pci_dev *dev) > if (off == 0 && (header[0] == 0x00 || header[0] == 0xff)) > goto error; > > + /* We can have max 4 tags: STRING_ID, RO, RW, END */ > + if (++num_tags > 4) > + goto error; > + > if (header[0] & PCI_VPD_LRDT) { > /* Large Resource Data Type Tag */ > if (pci_read_vpd_any(dev, off + 1, 2, &header[1]) != 2) { > Can this one be picked up for next?