In preempt kernel, BPF_PROG_TEST_RUN on raw_tp triggers:
[ 35.874974] BUG: using smp_processor_id() in preemptible [00000000]
code: new_name/87
[ 35.893983] caller is bpf_prog_test_run_raw_tp+0xd4/0x1b0
[ 35.900124] CPU: 1 PID: 87 Comm: new_name Not tainted 5.9.0-rc6-g615bd02bf #1
[ 35.907358] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1ubuntu1 04/01/2014
[ 35.916941] Call Trace:
[ 35.919660] dump_stack+0x77/0x9b
[ 35.923273] check_preemption_disabled+0xb4/0xc0
[ 35.928376] bpf_prog_test_run_raw_tp+0xd4/0x1b0
[ 35.933872] ? selinux_bpf+0xd/0x70
[ 35.937532] __do_sys_bpf+0x6bb/0x21e0
[ 35.941570] ? find_held_lock+0x2d/0x90
[ 35.945687] ? vfs_write+0x150/0x220
[ 35.949586] do_syscall_64+0x2d/0x40
[ 35.953443] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fix this by calling migrate_disable() before smp_processor_id().
Fixes: 1b4d60ec162f ("bpf: Enable BPF_PROG_TEST_RUN for raw_tracepoint")
Reported-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
Changes v1 => v2:
1. Keep rcu_read_lock/unlock() in original places. (Alexei)
2. Use get_cpu() instead of smp_processor_id(). (Alexei)
---
net/bpf/test_run.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index fde5db93507c4..c1c30a9f76f34 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -252,9 +252,7 @@ __bpf_prog_test_run_raw_tp(void *data)
struct bpf_raw_tp_test_run_info *info = data;
rcu_read_lock();
- migrate_disable();
info->retval = BPF_PROG_RUN(info->prog, info->ctx);
- migrate_enable();
rcu_read_unlock();
}
@@ -266,6 +264,7 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
__u32 ctx_size_in = kattr->test.ctx_size_in;
struct bpf_raw_tp_test_run_info info;
int cpu = kattr->test.cpu, err = 0;
+ int current_cpu;
/* doesn't support data_in/out, ctx_out, duration, or repeat */
if (kattr->test.data_in || kattr->test.data_out ||
@@ -293,27 +292,25 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
info.prog = prog;
+ current_cpu = get_cpu();
if ((kattr->test.flags & BPF_F_TEST_RUN_ON_CPU) == 0 ||
- cpu == smp_processor_id()) {
+ cpu == current_cpu) {
__bpf_prog_test_run_raw_tp(&info);
- } else {
+ } else if (cpu >= nr_cpu_ids || !cpu_online(cpu)) {
/* smp_call_function_single() also checks cpu_online()
* after csd_lock(). However, since cpu is from user
* space, let's do an extra quick check to filter out
* invalid value before smp_call_function_single().
*/
- if (cpu >= nr_cpu_ids || !cpu_online(cpu)) {
err = -ENXIO;
- goto out;
- }
-
+ } else {
err = smp_call_function_single(cpu, __bpf_prog_test_run_raw_tp,
&info, 1);
- if (err)
- goto out;
}
+ put_cpu();
- if (copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32)))
+ if (!err &&
+ copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32)))
err = -EFAULT;
out:
--
2.24.1
