Re: [PATCH] x86/resctrl: Fix uninitialized memory read when last CPU of domain goes offline

Ingo Molnar
2024-03-29T07:02:04Z

* Reinette Chatre <reinette.chatre@intel.com> wrote:

> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index c99f26ebe7a6..4f9ef35626a7 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -85,6 +85,10 @@ cpumask_any_housekeeping(const struct cpumask *mask, int exclude_cpu)
> if (cpu < nr_cpu_ids && !tick_nohz_full_cpu(cpu))
> return cpu;
>
> + /* Only continue if tick_nohz_full_mask has been initialized. */
> + if (!tick_nohz_full_enabled())
> + return cpu;
> +

So we already have this a few lines up:

if (!IS_ENABLED(CONFIG_NO_HZ_FULL))
return cpu;

And we can combine the two checks into a single one, with the patch
below, right?

Untested.

Thanks,

Ingo

==============>

Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/cpu/resctrl/internal.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index c99f26ebe7a6..1a8687f8073a 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -78,7 +78,8 @@ cpumask_any_housekeeping(const struct cpumask *mask, int exclude_cpu)
else
cpu = cpumask_any_but(mask, exclude_cpu);

- if (!IS_ENABLED(CONFIG_NO_HZ_FULL))
+ /* Only continue if tick_nohz_full_mask has been initialized. */
+ if (!tick_nohz_full_enabled())
return cpu;

/* If the CPU picked isn't marked nohz_full nothing more needs doing. */