Re: [PATCH 2/2] ALSA: compress_offload: avoid 64-bit get_user()

[Shengjiu Wang <shengjiu.wang@xxxxxxxxx>]

On Mon, Dec 16, 2024 at 5:34 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> On some architectures, get_user() cannot read a 64-bit user variable:
>
> arm-linux-gnueabi-ld: sound/core/compress_offload.o: in function `snd_compr_ioctl':
> compress_offload.c:(.text.snd_compr_ioctl+0x538): undefined reference to `__get_user_bad'
>
> Use an equivalent copy_from_user() instead.
>
> Fixes: 04177158cf98 ("ALSA: compress_offload: introduce accel operation mode")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Acked-by: Shengjiu Wang <shengjiu.wang@xxxxxxxxx>

Best regards
Shengjiu Wang

> ---
>  sound/core/compress_offload.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> index ec2485c00e49..1d6769a66810 100644
> --- a/sound/core/compress_offload.c
> +++ b/sound/core/compress_offload.c
> @@ -1180,9 +1180,9 @@ static int snd_compr_task_seq(struct snd_compr_stream *stream, unsigned long arg
>
>         if (stream->runtime->state != SNDRV_PCM_STATE_SETUP)
>                 return -EPERM;
> -       retval = get_user(seqno, (__u64 __user *)arg);
> -       if (retval < 0)
> -               return retval;
> +       retval = copy_from_user(&seqno, (__u64 __user *)arg, sizeof(seqno));
> +       if (retval)
> +               return -EFAULT;
>         retval = 0;
>         if (seqno == 0) {
>                 list_for_each_entry_reverse(task, &stream->runtime->tasks, list)
> --
> 2.39.5
>
>