Re: [PATCH 3/3] kernel/hung_task convert hung_task_panic boot parameter to sysctl

Kees Cook
2020-03-30T17:43:30Z

On Mon, Mar 30, 2020 at 01:55:35PM +0200, Vlastimil Babka wrote:
> We can now handle sysctl parameters on kernel command line and have
> infrastructure to convert legacy command line options that duplicate sysctl
> to become a sysctl alias.
>
> This patch converts the hung_task_panic parameter. Note that the sysctl handler
> is more strict and allows only 0 and 1, while the legacy parameter allowed
> any non-zero value. But there is little reason anyone would not be using 1.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

I'll let others double-check, but I think this change should be okay. If
not, we can adjust the sysctl handler to accept an arbitrary int.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
> Documentation/admin-guide/kernel-parameters.txt | 2 +-
> fs/proc/proc_sysctl.c | 1 +
> kernel/hung_task.c | 10 ----------
> 3 files changed, 2 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 81ff626fc700..e0b8840404a1 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1457,7 +1457,7 @@
> [KNL] Should the hung task detector generate panics.
> Format: <integer>
>
> - A nonzero value instructs the kernel to panic when a
> + A value of 1 instructs the kernel to panic when a
> hung task is detected. The default value is controlled
> by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
> option. The value selected by this boot parameter can
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index 97eb0b552bf8..77b1b844b02b 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -1743,6 +1743,7 @@ struct sysctl_alias {
> */
> static const struct sysctl_alias sysctl_aliases[] = {
> {"numa_zonelist_order", "vm.numa_zonelist_order" },
> + {"hung_task_panic", "kernel.hung_task_panic" },
> { }
> };
>
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 14a625c16cb3..b22b5eeab3cb 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -63,16 +63,6 @@ static struct task_struct *watchdog_task;
> unsigned int __read_mostly sysctl_hung_task_panic =
> CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
>
> -static int __init hung_task_panic_setup(char *str)
> -{
> - int rc = kstrtouint(str, 0, &sysctl_hung_task_panic);
> -
> - if (rc)
> - return rc;
> - return 1;
> -}
> -__setup("hung_task_panic=", hung_task_panic_setup);
> -
> static int
> hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
> {
> --
> 2.25.1
>

--
Kees Cook