[PATCH v4 03/24] PCI/sysfs: Only allow supported resource types in I/O and MMIO helpers

Krzysztof Wilczyński
2026-04-11T08:02:04Z

Currently, when the sysfs attributes for PCI resources are added
dynamically, the resource access callbacks are only set when the
underlying BAR type matches, using .read and .write for IORESOURCE_IO,
and .mmap for IORESOURCE_MEM or IORESOURCE_IO with arch_can_pci_mmap_io()
support. As such, when the callback is not set, the operation inherently
fails.

After the conversion to static attributes, visibility callbacks will
control which resource files appear for each BAR, but the callbacks
themselves will always be set.

Thus, add a type check to pci_resource_io() and pci_mmap_resource()
to return -EIO for an unsupported resource type.

Use the new pci_resource_is_io() and pci_resource_is_mem() helpers
for the type checks, replacing the open-coded bitwise flag tests and
also drop the local struct resource pointer in pci_mmap_resource().

Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
---
drivers/pci/pci-sysfs.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index ad3c17f86c7f..6783c6168445 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1108,20 +1108,24 @@ static int pci_mmap_resource(struct kobject *kobj, const struct bin_attribute *a
struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
int bar = (unsigned long)attr->private;
enum pci_mmap_state mmap_type;
- struct resource *res = pci_resource_n(pdev, bar);
int ret;

ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
if (ret)
return ret;

- if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
+ if (!pci_resource_is_mem(pdev, bar) &&
+ !(pci_resource_is_io(pdev, bar) && arch_can_pci_mmap_io()))
+ return -EIO;
+
+ if (pci_resource_is_mem(pdev, bar) &&
+ iomem_is_exclusive(pci_resource_start(pdev, bar)))
return -EINVAL;

if (!pci_mmap_fits(pdev, bar, vma, PCI_MMAP_SYSFS))
return -EINVAL;

- mmap_type = res->flags & IORESOURCE_MEM ? pci_mmap_mem : pci_mmap_io;
+ mmap_type = pci_resource_is_mem(pdev, bar) ? pci_mmap_mem : pci_mmap_io;

return pci_mmap_resource_range(pdev, bar, vma, mmap_type, write_combine);
}
@@ -1149,6 +1153,9 @@ static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj,
int bar = (unsigned long)attr->private;
unsigned long port = off;

+ if (!pci_resource_is_io(pdev, bar))
+ return -EIO;
+
port += pci_resource_start(pdev, bar);

if (port > pci_resource_end(pdev, bar))
--
2.53.0