[PATCH v7 08/17] PCI: Obey iomem restrictions for procfs mmap

Daniel Vetter
2020-11-27T16:44:58Z

There's three ways to access PCI BARs from userspace: /dev/mem, sysfs
files, and the old proc interface. Two check against
iomem_is_exclusive, proc never did. And with CONFIG_IO_STRICT_DEVMEM,
this starts to matter, since we don't want random userspace having
access to PCI BARs while a driver is loaded and using it.

Fix this by adding the same iomem_is_exclusive() check we already have
on the sysfs side in pci_mmap_resource().

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
References: 90a545e98126 ("restrict /dev/mem to idle io memory ranges")
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
--
v2: Improve commit message (Bjorn)
---
drivers/pci/proc.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index d35186b01d98..3a2f90beb4cb 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -274,6 +274,11 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
else
return -EINVAL;
}
+
+ if (dev->resource[i].flags & IORESOURCE_MEM &&
+ iomem_is_exclusive(dev->resource[i].start))
+ return -EINVAL;
+
ret = pci_mmap_page_range(dev, i, vma,
fpriv->mmap_state, write_combine);
if (ret < 0)