[PATCH bpf-next] bpf: fix raw_tp test run in preempt kernel
From: Song Liu <hidden>
Date: 2020-09-29 22:50:25
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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(); } 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:
--
2.24.1