bpf: Reject bpf_timer for PREEMPT_RT

When enable CONFIG_PREEMPT_RT, the kernel will warn when run timer
selftests by './test_progs -t timer':

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48

In order to avoid such warning, reject bpf_timer in verifier when
PREEMPT_RT is enabled.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20250910125740.52172-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c89e2b1bc644b744cee4c72b29357f63f435fb34..9fb1f957a09374e4d148402572b872bec930f34c 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8547,6 +8547,10 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno,
                verifier_bug(env, "Two map pointers in a timer helper");
                return -EFAULT;
        }
+       if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+               verbose(env, "bpf_timer cannot be used for PREEMPT_RT.\n");
+               return -EOPNOTSUPP;
+       }
        meta->map_uid = reg->map_uid;
        meta->map_ptr = map;
        return 0;