| Message ID | 20200929225013.930-1-songliubraving@fb.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [bpf-next] bpf: fix raw_tp test run in preempt kernel | expand |
On Tue, Sep 29, 2020 at 03:50:13PM -0700, Song Liu wrote: > 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 <songliubraving@fb.com> > --- > 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. > } > > 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 >
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(); } 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()) { __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 && + copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32))) err = -EFAULT; out:
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 <songliubraving@fb.com> --- net/bpf/test_run.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-)