On Thu, May 02, 2019 at 04:52:21PM -0400, Joel Savitz wrote:
> When PR_GET_TASK_SIZE is passed to prctl, the kernel will attempt to
> copy the value of TASK_SIZE to the userspace address in arg2.
>
> Suggested-by: Alexey Dobriyan <adobri...@gmail.com>
> Signed-off-by: Joel Savitz <jsav...@redhat.com>
> ---
> include/uapi/linux/prctl.h | 3 +++
> kernel/sys.c | 10 ++++++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
> index 094bb03b9cc2..2335fe0a8db8 100644
> --- a/include/uapi/linux/prctl.h
> +++ b/include/uapi/linux/prctl.h
> @@ -229,4 +229,7 @@ struct prctl_mm_map {
> # define PR_PAC_APDBKEY (1UL << 3)
> # define PR_PAC_APGAKEY (1UL << 4)
>
> +/* Get the process virtual memory size */
> +#define PR_GET_TASK_SIZE 55
> +
> #endif /* _LINUX_PRCTL_H */
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 12df0e5434b8..7ced7dbd035d 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2252,6 +2252,13 @@ static int propagate_has_child_subreaper(struct
> task_struct *p, void *data)
> return 1;
> }
>
> +static int prctl_get_tasksize(void __user * uaddr)
> +{
> + unsigned long task_size = TASK_SIZE;
> + return copy_to_user(uaddr, &task_size, sizeof(unsigned long))
> + ? -EFAULT : 0;
Minor pick: I would keep the all of the ternary statement above in the
same line, to help on improving readability (even though it bursts a
little longer than 80 columns of text)
> +}
> +
> int __weak arch_prctl_spec_ctrl_get(struct task_struct *t, unsigned long
> which)
> {
> return -EINVAL;
> @@ -2486,6 +2493,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long,
> arg2, unsigned long, arg3,
> return -EINVAL;
> error = PAC_RESET_KEYS(me, arg2);
> break;
> + case PR_GET_TASK_SIZE:
> + error = prctl_get_tasksize((void *)arg2) ;
> + break;
> default:
> error = -EINVAL;
> break;
> --
> 2.18.1
>
