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From:   Jann Horn <jannh@google.com>
Date:   Thu, 5 Jul 2018 22:56:00 +0200
Message-ID: <CAG48ez1Ze1Q08HtyC8PyhW5msQ8qwFDy6eDj8s9k_j4vmG7nJw@mail.gmail.com>
Subject: Re: [PATCH 2/2] uio: fix crash after the device is unregistered
To:     xiubli@redhat.com
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        pkalever@redhat.com, pkarampu@redhat.com, atumball@redhat.com,
        sabose@redhat.com, mchristi@redhat.com
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On Thu, Jul 5, 2018 at 10:53 PM <xiubli@redhat.com> wrote:
>
> From: Xiubo Li <xiubli@redhat.com>
>
> For the target_core_user use case, after the device is unregistered
> it maybe still opened in user space, then the kernel will crash, like:
>
[...]
>
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  drivers/uio/uio.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 86 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index 33c3bfe..2b9268a 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
[...]
> @@ -720,30 +775,46 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
>
>         vma->vm_private_data = idev;
>
> +       mutex_lock(&idev->info_lock);
> +       if (!idev->info) {
> +               ret = -EINVAL;
> +               goto out;
> +       }
> +
>         mi = uio_find_mem_index(vma);
> -       if (mi < 0)
> -               return -EINVAL;
> +       if (mi < 0) {
> +               ret = -EINVAL;
> +               goto out;
> +       }
>
>         requested_pages = vma_pages(vma);
>         actual_pages = ((idev->info->mem[mi].addr & ~PAGE_MASK)
>                         + idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT;
> -       if (requested_pages > actual_pages)
> -               return -EINVAL;
> +       if (requested_pages > actual_pages) {
> +               ret = -EINVAL;
> +               goto out;
> +       }
>
>         if (idev->info->mmap) {
>                 ret = idev->info->mmap(idev->info, vma);
> -               return ret;
> +               goto out;
>         }
>
>         switch (idev->info->mem[mi].memtype) {
>                 case UIO_MEM_PHYS:
> -                       return uio_mmap_physical(vma);
> +                       ret = uio_mmap_physical(vma);
> +                       break;
>                 case UIO_MEM_LOGICAL:
>                 case UIO_MEM_VIRTUAL:
> -                       return uio_mmap_logical(vma);
> +                       ret = uio_mmap_logical(vma);
> +                       break;
>                 default:
> -                       return -EINVAL;
> +                       ret = -EINVAL;
>         }
> +
> +out:
> +       mutex_lock(&idev->info_lock);

This is probably supposed to be mutex_unlock(...)?