[PATCH] PCI: sysfs: Reject unaligned resource I/O port accesses

[Deepanshu Kartikey]

pci_resource_io() validates that off+count stays within the BAR's
range but never checks that the resulting port is aligned to the
access size. A pwrite64()/pread64() on a resourceN file with an odd
offset and count=2 or count=4 reaches outw()/outl() with a misaligned
address. On arm64 this becomes a store/load to a Device-memory
mapping (PCI_IOBASE + port), which architecturally requires natural
alignment, causing an alignment fault and kernel oops.

Reject misaligned accesses before they reach the low-level accessor.

Reported-by: syzbot+7134530b25073b4ef373@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=7134530b25073b4ef373
Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>
---
 drivers/pci/pci-sysfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 5ec0b245a69b..72f0404a34e9 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1175,6 +1175,9 @@ static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj,
 	if (port + count - 1 > pci_resource_end(pdev, bar))
 		return -EINVAL;
 
+	if (!IS_ALIGNED(port, count))
+		return -EINVAL;
+
 	switch (count) {
 	case 1:
 		if (write)
-- 
2.43.0