linux-kernel - Re: [PATCH v2 3/3] PCI/sysfs: Prohibit unaligned access to I/O port on non-x86

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Message-ID: <2bc52d2a-7934-df63-6463-7bc91a526ab4@linux.intel.com>
Date: Mon, 29 Dec 2025 11:36:48 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Ziming Du <duziming2@...wei.com>
cc: bhelgaas@...gle.com, jbarnes@...tuousgeek.org, chrisw@...hat.com, 
    alex.williamson@...hat.com, linux-pci@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>, liuyongqiang13@...wei.com
Subject: Re: [PATCH v2 3/3] PCI/sysfs: Prohibit unaligned access to I/O port
 on non-x86

On Wed, 24 Dec 2025, Ziming Du wrote:

> From: Yongqiang Liu <liuyongqiang13@...wei.com>
> 
> Unaligned access is harmful for non-x86 archs such as arm64. When we
> use pwrite or pread to access the I/O port resources with unaligned
> offset, system will crash as follows:
> 
> Unable to handle kernel paging request at virtual address fffffbfffe8010c1
> Internal error: Oops: 0000000096000061 [#1] SMP
> Call trace:
>  _outw include/asm-generic/io.h:594 [inline]
>  logic_outw+0x54/0x218 lib/logic_pio.c:305
>  pci_resource_io drivers/pci/pci-sysfs.c:1157 [inline]
>  pci_write_resource_io drivers/pci/pci-sysfs.c:1191 [inline]
>  pci_write_resource_io+0x208/0x260 drivers/pci/pci-sysfs.c:1181
>  sysfs_kf_bin_write+0x188/0x210 fs/sysfs/file.c:158
>  kernfs_fop_write_iter+0x2e8/0x4b0 fs/kernfs/file.c:338
>  vfs_write+0x7bc/0xac8 fs/read_write.c:586
>  ksys_write+0x12c/0x270 fs/read_write.c:639
>  __arm64_sys_write+0x78/0xb8 fs/read_write.c:648
> 
> Powerpc seems affected as well, so prohibit the unaligned access
> on non-x86 archs.
> 
> Fixes: 8633328be242 ("PCI: Allow read/write access to sysfs I/O port resources")
> Signed-off-by: Yongqiang Liu <liuyongqiang13@...wei.com>
> Signed-off-by: Ziming Du <duziming2@...wei.com>
> ---
>  drivers/pci/pci-sysfs.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 7e697b82c5e1..c44a9c4a91ab 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1166,12 +1166,20 @@ static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj,
>  			*(u8 *)buf = inb(port);
>  		return 1;
>  	case 2:
> +#if !defined(CONFIG_X86)
> +		if (!IS_ALIGNED(port, count))
> +			return -EFAULT;
> +#endif
>  		if (write)
>  			outw(*(u16 *)buf, port);
>  		else
>  			*(u16 *)buf = inw(port);
>  		return 2;
>  	case 4:
> +#if !defined(CONFIG_X86)
> +		if (!IS_ALIGNED(port, count))
> +			return -EFAULT;
> +#endif
>  		if (write)
>  			outl(*(u32 *)buf, port);
>  		else
> 

To use IS_ALIGNED(), you need to add:

#include <linux/align.h>

-- 
 i.