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

[Bjorn Helgaas <helgaas@kernel.org>]

On Sun, Aug 09, 2026 at 10:29:46AM +0530, Deepanshu Kartikey wrote:
> 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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=7134530b25073b4ef373
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>

Applied to pci/sysfs for v7.4, thanks!

Hopefully the last patch for v7.4.

> ---
>  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
>