Re: [PATCH 2/2] PM / sleep: handle the compat case in snapshot_set_swap_area

From: Rafael J. Wysocki
Date: Mon Apr 06 2020 - 15:45:31 EST


On Mon, Apr 6, 2020 at 1:58 PM Christoph Hellwig <hch@xxxxxx> wrote:
>
> Use in_compat_syscall to copy directly from the 32-bit ABI structure.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> kernel/power/user.c | 54 ++++++++++++++++++---------------------------
> 1 file changed, 22 insertions(+), 32 deletions(-)
>
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index 0cb555f526e4..7959449765d9 100644
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -196,28 +196,44 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf,
> return res;
> }
>
> +struct compat_resume_swap_area {
> + compat_loff_t offset;
> + u32 dev;
> +} __packed;
> +
> static int snapshot_set_swap_area(struct snapshot_data *data,
> void __user *argp)
> {
> - struct resume_swap_area swap_area;
> sector_t offset;
> dev_t swdev;
>
> if (swsusp_swap_in_use())
> return -EPERM;
> - if (copy_from_user(&swap_area, argp, sizeof(swap_area)))
> - return -EFAULT;
> +
> + if (in_compat_syscall()) {
> + struct compat_resume_swap_area swap_area;
> +
> + if (copy_from_user(&swap_area, argp, sizeof(swap_area)))
> + return -EFAULT;
> + swdev = new_decode_dev(swap_area.dev);
> + offset = swap_area.offset;
> + } else {
> + struct resume_swap_area swap_area;
> +
> + if (copy_from_user(&swap_area, argp, sizeof(swap_area)))
> + return -EFAULT;
> + swdev = new_decode_dev(swap_area.dev);
> + offset = swap_area.offset;
> + }
>
> /*
> * User space encodes device types as two-byte values,
> * so we need to recode them
> */
> - swdev = new_decode_dev(swap_area.dev);
> if (!swdev) {
> data->swap = -1;
> return -EINVAL;
> }
> - offset = swap_area.offset;
> data->swap = swap_type_of(swdev, offset, NULL);
> if (data->swap < 0)
> return -ENODEV;
> @@ -394,12 +410,6 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
> }
>
> #ifdef CONFIG_COMPAT
> -
> -struct compat_resume_swap_area {
> - compat_loff_t offset;
> - u32 dev;
> -} __packed;
> -
> static long
> snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> {
> @@ -410,33 +420,13 @@ snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> case SNAPSHOT_AVAIL_SWAP_SIZE:
> case SNAPSHOT_ALLOC_SWAP_PAGE:
> case SNAPSHOT_CREATE_IMAGE:
> + case SNAPSHOT_SET_SWAP_AREA:
> return snapshot_ioctl(file, cmd,
> (unsigned long) compat_ptr(arg));
> -
> - case SNAPSHOT_SET_SWAP_AREA: {
> - struct compat_resume_swap_area __user *u_swap_area =
> - compat_ptr(arg);
> - struct resume_swap_area swap_area;
> - mm_segment_t old_fs;
> - int err;
> -
> - err = get_user(swap_area.offset, &u_swap_area->offset);
> - err |= get_user(swap_area.dev, &u_swap_area->dev);
> - if (err)
> - return -EFAULT;
> - old_fs = get_fs();
> - set_fs(KERNEL_DS);
> - err = snapshot_ioctl(file, SNAPSHOT_SET_SWAP_AREA,
> - (unsigned long) &swap_area);
> - set_fs(old_fs);
> - return err;
> - }
> -
> default:
> return snapshot_ioctl(file, cmd, arg);
> }
> }
> -
> #endif /* CONFIG_COMPAT */
>
> static const struct file_operations snapshot_fops = {
> --

Applied along with the [1/2] as 5.7-rc material, thanks!