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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id bk25-20020a0560001d9900b0020589956916sm641368wrb.78.2022.03.23.02.13.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Mar 2022 02:13:06 -0700 (PDT) Date: Wed, 23 Mar 2022 09:13:02 +0000 From: Keir Fraser To: Jason Wang Cc: "Michael S. Tsirkin" , kernel-team@android.com, virtualization , linux-kernel Subject: Re: [PATCH v2] virtio: pci: sanity check bar indexes Message-ID: References: <20220322151952.2950143-1-keirf@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 23, 2022 at 03:57:59PM +0800, Jason Wang wrote: > On Tue, Mar 22, 2022 at 11:20 PM Keir Fraser wrote: > > > > The bar index is used as an index into the device's resource list > > and should be checked as within range for a standard bar. > > > > Also clean up an existing check to consistently use PCI_STD_NUM_BARS. > > > > Signed-off-by: Keir Fraser > > --- > > drivers/virtio/virtio_pci_modern.c | 10 ++++++++-- > > drivers/virtio/virtio_pci_modern_dev.c | 8 +++++++- > > 2 files changed, 15 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c > > index 5455bc041fb6..84bace98dff5 100644 > > --- a/drivers/virtio/virtio_pci_modern.c > > +++ b/drivers/virtio/virtio_pci_modern.c > > @@ -293,7 +293,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id, > > > > for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR); pos > 0; > > pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) { > > - u8 type, cap_len, id; > > + u8 type, cap_len, id, res_bar; > > u32 tmp32; > > u64 res_offset, res_length; > > > > @@ -317,7 +317,12 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id, > > > > /* Type, and ID match, looks good */ > > pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap, > > - bar), bar); > > + bar), &res_bar); > > + if (res_bar >= PCI_STD_NUM_BARS) { > > + dev_err(&dev->dev, "%s: shm cap with bad bar: %d\n", > > + __func__, res_bar); > > + continue; > > + } > > > > /* Read the lower 32bit of length and offset */ > > pci_read_config_dword(dev, pos + offsetof(struct virtio_pci_cap, > > @@ -337,6 +342,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id, > > length_hi), &tmp32); > > res_length |= ((u64)tmp32) << 32; > > > > + *bar = res_bar; > > *offset = res_offset; > > *len = res_length; > > > > diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c > > index e8b3ff2b9fbc..a6911d1e212a 100644 > > --- a/drivers/virtio/virtio_pci_modern_dev.c > > +++ b/drivers/virtio/virtio_pci_modern_dev.c > > @@ -35,6 +35,12 @@ vp_modern_map_capability(struct virtio_pci_modern_device *mdev, int off, > > pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap, length), > > &length); > > > > + if (bar >= PCI_STD_NUM_BARS) { > > + dev_err(&dev->dev, > > + "virtio_pci: bad capability bar %u\n", bar); > > + return NULL; > > + } > > + > > if (length <= start) { > > dev_err(&dev->dev, > > "virtio_pci: bad capability len %u (>%u expected)\n", > > @@ -120,7 +126,7 @@ static inline int virtio_pci_find_capability(struct pci_dev *dev, u8 cfg_type, > > &bar); > > > > /* Ignore structures with reserved BAR values */ > > - if (bar > 0x5) > > + if (bar >= PCI_STD_NUM_BARS) > > continue; > > Just notice that the spec said: > > " > values 0x0 to 0x5 specify a Base Address register (BAR) belonging to > the function located beginning at 10h in PCI Configuration Space and > used to map the structure into Memory or I/O Space. The BAR is > permitted to be either 32-bit or 64-bit, it can map Memory Space or > I/O Space. > > Any other value is reserved for future use. > " > > So we probably need to stick 0x5 instead of 0x6 (PCI_STD_NUM_BARS) for > this and other places. The comparison(s) are changed to greater-or-equal, so they are logically equivalent to the old check against naked 0x5 while documenting the intent better. > Thanks > > > > > if (type == cfg_type) { > > -- > > 2.35.1.894.gb6a874cedc-goog > > >