Messages in this thread | | | Subject | Re: [PATCH] bpf: skip task with pid=1 in send_signal_common() | From | Daniel Borkmann <> | Date | Fri, 6 Jan 2023 22:54:32 +0100 |
| |
On 1/6/23 8:44 PM, Stanislav Fomichev wrote: > On Fri, Jan 6, 2023 at 12:48 AM Hao Sun <sunhao.th@gmail.com> wrote: >> >> The following kernel panic can be triggered when a task with pid=1 >> attach a prog that attempts to send killing signal to itself, also >> see [1] for more details: >> >> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b >> CPU: 3 PID: 1 Comm: systemd Not tainted 6.1.0-09652-g59fe41b5255f #148 >> Call Trace: >> <TASK> >> __dump_stack lib/dump_stack.c:88 [inline] >> dump_stack_lvl+0x100/0x178 lib/dump_stack.c:106 >> panic+0x2c4/0x60f kernel/panic.c:275 >> do_exit.cold+0x63/0xe4 kernel/exit.c:789 >> do_group_exit+0xd4/0x2a0 kernel/exit.c:950 >> get_signal+0x2460/0x2600 kernel/signal.c:2858 >> arch_do_signal_or_restart+0x78/0x5d0 arch/x86/kernel/signal.c:306 >> exit_to_user_mode_loop kernel/entry/common.c:168 [inline] >> exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 >> __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] >> syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 >> do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86 >> entry_SYSCALL_64_after_hwframe+0x63/0xcd >> >> So skip task with pid=1 in bpf_send_signal_common() to avoid the panic. >> >> [1] https://lore.kernel.org/bpf/20221222043507.33037-1-sunhao.th@gmail.com >> >> Signed-off-by: Hao Sun <sunhao.th@gmail.com> > > Acked-by: Stanislav Fomichev <sdf@google.com>
Looks good, agree & applied. These three tests could actually be refactored and also reused in bpf_probe_write_user() given also the latter should have no business to mess with pid 1.
>> kernel/trace/bpf_trace.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c >> index 23ce498bca97..ed21ab9fe846 100644 >> --- a/kernel/trace/bpf_trace.c >> +++ b/kernel/trace/bpf_trace.c >> @@ -844,6 +844,9 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type) >> */ >> if (unlikely(current->flags & (PF_KTHREAD | PF_EXITING))) >> return -EPERM; >> + /* Task should not be pid=1 to avoid kernel panic. */ >> + if (unlikely(is_global_init(current))) >> + return -EPERM; >> if (unlikely(!nmi_uaccess_okay())) >> return -EPERM; >> >> >> base-commit: 4aea86b4033f92f01547e6d4388d4451ae9b0980 >> -- >> 2.39.0 >>
| |