diff options
| author | Andrea Righi <arighi@nvidia.com> | 2025-09-04 20:23:48 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2025-09-04 10:27:16 -1000 |
| commit | 47d9f8212826753c482df8189d18ca212eb5ae73 (patch) | |
| tree | 8f68e9e2f4632f54fc5ca346f374a011bd49309a | |
| parent | a08b4dcad9fae495bcd88b91fb3410abf77d268e (diff) | |
sched_ext: Fix NULL dereference in scx_bpf_cpu_rq() warning
When printing the deprecation warning for scx_bpf_cpu_rq(), we may hit a
NULL pointer dereference if the kfunc is called before a BPF scheduler
is fully attached, for example, when invoked from a BPF timer or during
ops.init():
[ 50.752775] BUG: kernel NULL pointer dereference, address: 0000000000000331
...
[ 50.764205] RIP: 0010:scx_bpf_cpu_rq+0x30/0xa0
...
[ 50.787661] Call Trace:
[ 50.788398] <TASK>
[ 50.789061] bpf_prog_08f7fd2dcb187aaf_wakeup_timerfn+0x75/0x1a8
[ 50.792477] bpf_timer_cb+0x7e/0x140
[ 50.796003] hrtimer_run_softirq+0x91/0xe0
[ 50.796952] handle_softirqs+0xce/0x3c0
[ 50.799087] run_ksoftirqd+0x3e/0x70
[ 50.800197] smpboot_thread_fn+0x133/0x290
[ 50.802320] kthread+0x115/0x220
[ 50.804984] ret_from_fork+0x17a/0x1d0
[ 50.806920] ret_from_fork_asm+0x1a/0x30
[ 50.807799] </TASK>
Fix this by only printing the warning once the scheduler is fully
registered.
Fixes: 5c48d88fe0049 ("sched_ext: deprecation warn for scx_bpf_cpu_rq()")
Cc: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | kernel/sched/ext.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 4160a4a7af67..477eccf02338 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -6351,17 +6351,20 @@ __bpf_kfunc s32 scx_bpf_task_cpu(const struct task_struct *p) */ __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu) { - struct scx_sched *sch = scx_root; + struct scx_sched *sch; if (!kf_cpu_valid(cpu, NULL)) return NULL; - if (!sch->warned_deprecated_rq) { + rcu_read_lock(); + sch = rcu_dereference(scx_root); + if (likely(sch) && !sch->warned_deprecated_rq) { printk_deferred(KERN_WARNING "sched_ext: %s() is deprecated; " "use scx_bpf_locked_rq() when holding rq lock " "or scx_bpf_cpu_curr() to read remote curr safely.\n", __func__); sch->warned_deprecated_rq = true; } + rcu_read_unlock(); return cpu_rq(cpu); } |