The following kernel panic can be triggered when a task with pid=1 attaches 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
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| @@ -848,6 +848,9 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type) · 847 unmodified lines | |||
| 848 | return -EPERM; | 848 | return -EPERM; |
| 849 | if (unlikely(!nmi_uaccess_okay())) | 849 | if (unlikely(!nmi_uaccess_okay())) |
| 850 | return -EPERM; | 850 | return -EPERM; |
| 851 | /* Task should not be pid=1 to avoid kernel panic. */ | ||
| 852 | if (unlikely(is_global_init(current))) | ||
| 853 | return -EPERM; | ||
| 851 | 854 | ||
| 852 | if (irqs_disabled()) { | 855 | if (irqs_disabled()) { |
| 853 | /* Do an early check on signal validity. Otherwise, | 856 | /* Do an early check on signal validity. Otherwise, |