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@xxxxxxxxxxxxxxx # v6.12+
Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
(cherry picked from commit 9360dfe4cbd62ff1eb8217b815964931523b75b3)
---
kernel/sched/ext.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 325fd5b9d4715..e5cab54dfdd14 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -6052,6 +6052,9 @@ __bpf_kfunc_start_defs();
__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))
+ goto prev_cpu;
+
if (!static_branch_likely(&scx_builtin_idle_enabled)) {
scx_ops_error("built-in idle tracking is disabled");
goto prev_cpu;
--
2.48.1
