bpf: Reject bpf_timer for PREEMPT_RT

[ Upstream commit e25ddfb388c8b7e5f20e3bf38d627fb485003781 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ead1811534a0d554f692082ac72f0d8abe77f25d..276a0de9a1bb20b442bfefd61c4782de3809f9ee 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5733,6 +5733,10 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno,
                verbose(env, "verifier bug. Two map pointers in a timer helper\n");
                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;