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sched_ext: Reject NULL-sch callers in scx_bpf_task_set_slice/dsq_vtime 

scx_prog_sched(aux) returns NULL for TRACING / SYSCALL BPF progs that
have no struct_ops association when the root scheduler has sub_attach
set. scx_bpf_task_set_slice() and scx_bpf_task_set_dsq_vtime() pass
that NULL into scx_task_on_sched(sch, p), which under
CONFIG_EXT_SUB_SCHED is rcu_access_pointer(p->scx.sched) == sch. For
any non-scx task p->scx.sched is NULL, so NULL == NULL returns true
and the authority gate is bypassed - a privileged but
non-struct_ops-associated prog can poke p->scx.slice /
p->scx.dsq_vtime on arbitrary tasks.

Reject !sch up front so the gate only admits callers with a resolved
scheduler.

Fixes: 245d09c594 ("sched_ext: Enforce scheduler ownership when updating slice and dsq_vtime")
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
master
Tejun Heo 2026-04-24 14:31:36 -10:00
parent ea7c716a24
commit 05b4a9a9bc
1 changed files with 2 additions and 2 deletions
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4
kernel/sched/ext.c
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@ -8640,7 +8640,7 @@ __bpf_kfunc bool scx_bpf_task_set_slice(struct task_struct *p, u64 slice,
guard(rcu)();
sch = scx_prog_sched(aux);
if (unlikely(!scx_task_on_sched(sch, p)))
if (unlikely(!sch || !scx_task_on_sched(sch, p)))
return false;
p->scx.slice = slice;
@ -8663,7 +8663,7 @@ __bpf_kfunc bool scx_bpf_task_set_dsq_vtime(struct task_struct *p, u64 vtime,
guard(rcu)();
sch = scx_prog_sched(aux);
if (unlikely(!scx_task_on_sched(sch, p)))
if (unlikely(!sch || !scx_task_on_sched(sch, p)))
return false;
p->scx.dsq_vtime = vtime;