* [PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
@ 2025-03-02 22:09 Andrea Righi
2025-03-03 16:11 ` Tejun Heo
0 siblings, 1 reply; 3+ messages in thread
From: Andrea Righi @ 2025-03-02 22:09 UTC (permalink / raw)
To: Tejun Heo, David Vernet, Changwoo Min; +Cc: linux-kernel
If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids
range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel
crash.
To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and
trigger an scx error if an invalid CPU is specified.
Fixes: f0e1a0643a59b ("sched_ext: Implement BPF extensible scheduler class")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Andrea Righi <arighi@nvidia.com>
---
kernel/sched/ext.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 0f1da199cfc7c..88b2ea58ff942 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6422,6 +6422,11 @@ static bool check_builtin_idle_enabled(void)
__bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
u64 wake_flags, bool *is_idle)
{
+ if (!ops_cpu_valid(prev_cpu, NULL)) {
+ prev_cpu = cpumask_any(p->cpus_ptr);
+ goto prev_cpu;
+ }
+
if (!check_builtin_idle_enabled())
goto prev_cpu;
--
2.48.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
2025-03-02 22:09 [PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl() Andrea Righi
@ 2025-03-03 16:11 ` Tejun Heo
2025-03-03 17:25 ` Andrea Righi
0 siblings, 1 reply; 3+ messages in thread
From: Tejun Heo @ 2025-03-03 16:11 UTC (permalink / raw)
To: Andrea Righi; +Cc: David Vernet, Changwoo Min, linux-kernel
Hello,
On Sun, Mar 02, 2025 at 11:09:03PM +0100, Andrea Righi wrote:
> If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids
> range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel
> crash.
>
> To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and
> trigger an scx error if an invalid CPU is specified.
>
> Fixes: f0e1a0643a59b ("sched_ext: Implement BPF extensible scheduler class")
> Cc: stable@vger.kernel.org # v6.12+
> Signed-off-by: Andrea Righi <arighi@nvidia.com>
> ---
> kernel/sched/ext.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 0f1da199cfc7c..88b2ea58ff942 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -6422,6 +6422,11 @@ static bool check_builtin_idle_enabled(void)
> __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
> u64 wake_flags, bool *is_idle)
> {
> + if (!ops_cpu_valid(prev_cpu, NULL)) {
> + prev_cpu = cpumask_any(p->cpus_ptr);
> + goto prev_cpu;
I'd just return the invalid prev_cpu. The scheduler is getting aborted
anyway.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
2025-03-03 16:11 ` Tejun Heo
@ 2025-03-03 17:25 ` Andrea Righi
0 siblings, 0 replies; 3+ messages in thread
From: Andrea Righi @ 2025-03-03 17:25 UTC (permalink / raw)
To: Tejun Heo; +Cc: David Vernet, Changwoo Min, linux-kernel
On Mon, Mar 03, 2025 at 06:11:15AM -1000, Tejun Heo wrote:
> Hello,
>
> On Sun, Mar 02, 2025 at 11:09:03PM +0100, Andrea Righi wrote:
> > If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids
> > range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel
> > crash.
> >
> > To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and
> > trigger an scx error if an invalid CPU is specified.
> >
> > Fixes: f0e1a0643a59b ("sched_ext: Implement BPF extensible scheduler class")
> > Cc: stable@vger.kernel.org # v6.12+
> > Signed-off-by: Andrea Righi <arighi@nvidia.com>
> > ---
> > kernel/sched/ext.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> > index 0f1da199cfc7c..88b2ea58ff942 100644
> > --- a/kernel/sched/ext.c
> > +++ b/kernel/sched/ext.c
> > @@ -6422,6 +6422,11 @@ static bool check_builtin_idle_enabled(void)
> > __bpf_kfunc s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
> > u64 wake_flags, bool *is_idle)
> > {
> > + if (!ops_cpu_valid(prev_cpu, NULL)) {
> > + prev_cpu = cpumask_any(p->cpus_ptr);
> > + goto prev_cpu;
>
> I'd just return the invalid prev_cpu. The scheduler is getting aborted
> anyway.
>
> Thanks.
Yeah, makes sense. I'll send a new patch soon.
Thanks,
-Andrea
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-03-02 22:09 [PATCH] sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl() Andrea Righi
2025-03-03 16:11 ` Tejun Heo
2025-03-03 17:25 ` Andrea Righi
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