Re: [PATCH bpf-next] bpf: fix raw_tp test run in preempt kernel
From: Alexei Starovoitov <hidden>
Date: 2020-09-30 00:00:13
Also in:
bpf
On Tue, Sep 29, 2020 at 03:50:13PM -0700, Song Liu wrote:
quoted hunk ↗ jump to hunk
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@kernel.org> Signed-off-by: Song Liu <redacted> --- net/bpf/test_run.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-)diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index fde5db93507c4..3ea05a5daf544 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c@@ -251,11 +251,7 @@ __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();
I would keep rcu_read_lock here, since there is no need to expand its scope.
quoted hunk ↗ jump to hunk
} int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,@@ -293,27 +289,27 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog, info.prog = prog; + rcu_read_lock(); + migrate_disable(); if ((kattr->test.flags & BPF_F_TEST_RUN_ON_CPU) == 0 || cpu == smp_processor_id()) {
may be use get_cpu/put_cpu instead?
__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;
}
+ migrate_enable();
+ rcu_read_unlock();
- if (copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32)))
+ if (err == 0 &&!err would be canonical.
+ copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32))) err = -EFAULT; out: -- 2.24.1