linux-kernel - Re: [PATCH] vfio: Fix ksize arg while copying user struct in vfio_df_ioctl_bind

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Message-ID: <5e24cb1e-4ee8-166b-48c7-88fa6857c8dc@huawei.com>
Date: Fri, 31 Oct 2025 09:34:18 +0800
From: liulongfang <liulongfang@...wei.com>
To: Raghavendra Rao Ananta <rananta@...gle.com>, Jason Gunthorpe
	<jgg@...pe.ca>, Alex Williamson <alex.williamson@...hat.com>, David Matlack
	<dmatlack@...gle.com>
CC: Josh Hilke <jrhilke@...gle.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vfio: Fix ksize arg while copying user struct in
 vfio_df_ioctl_bind_iommufd()

On 2025/10/31 1:12, Raghavendra Rao Ananta wrote:
> For the cases where user includes a non-zero value in 'token_uuid_ptr'
> field of 'struct vfio_device_bind_iommufd', the copy_struct_from_user()
> in vfio_df_ioctl_bind_iommufd() fails with -E2BIG. For the 'minsz' passed,
> copy_struct_from_user() expects the newly introduced field to be zero-ed,
> which would be incorrect in this case.
> 
> Fix this by passing the actual size of the kernel struct. If working
> with a newer userspace, copy_struct_from_user() would copy the
> 'token_uuid_ptr' field, and if working with an old userspace, it would
> zero out this field, thus still retaining backward compatibility.
> 
> Fixes: 86624ba3b522 ("vfio/pci: Do vf_token checks for VFIO_DEVICE_BIND_IOMMUFD")

Hi Ananta,

This patch also has another bug: in the hisi_acc_vfio_pci.c driver, It have two "struct vfio_device_ops"
Only one of them, "hisi_acc_vfio_pci_ops" has match_token_uuid added,
while the other one, "hisi_acc_vfio_pci_migrn_ops", is missing it.
This will cause a QEMU crash (call trace) when QEMU tries to start the device.

Could you please help include this fix in your patchset as well?

--- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
+++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
@@ -1637,6 +1637,7 @@ static const struct vfio_device_ops hisi_acc_vfio_pci_migrn_ops = {
 	.mmap = hisi_acc_vfio_pci_mmap,
 	.request = vfio_pci_core_request,
 	.match = vfio_pci_core_match,
+	.match_token_uuid = vfio_pci_core_match_token_uuid,
 	.bind_iommufd = vfio_iommufd_physical_bind,
 	.unbind_iommufd = vfio_iommufd_physical_unbind,
 	.attach_ioas = vfio_iommufd_physical_attach_ioas,

Thanks.
Longfang.

> Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
> ---
>  drivers/vfio/device_cdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
> index 480cac3a0c274..8ceca24ac136c 100644
> --- a/drivers/vfio/device_cdev.c
> +++ b/drivers/vfio/device_cdev.c
> @@ -99,7 +99,7 @@ long vfio_df_ioctl_bind_iommufd(struct vfio_device_file *df,
>  		return ret;
>  	if (user_size < minsz)
>  		return -EINVAL;
> -	ret = copy_struct_from_user(&bind, minsz, arg, user_size);
> +	ret = copy_struct_from_user(&bind, sizeof(bind), arg, user_size);
>  	if (ret)
>  		return ret;
>  
> 
> base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
>