kernel panic: Attempted to kill init!

From: Hao Sun <sunhao.th@gmail.com>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com,
	andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
	yhs@fb.com, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org, davem@davemloft.net,
	linux-kernel@vger.kernel.org, Hao Sun <sunhao.th@gmail.com>
Subject: kernel panic: Attempted to kill init!
Date: Thu, 22 Dec 2022 12:35:07 +0800	[thread overview]
Message-ID: <20221222043507.33037-1-sunhao.th@gmail.com> (raw)

Hi,

This crash can be triggered by executing the C reproducer for
multiple times, which just keep loading the following prog as
raw tracepoint into kmem_cache_free().

The prog send SIGSEGV to current via bpf_send_signal_thread(),
after load this, whoever tries to free mem would trigger this,
kernel crashed when this happens to init. 

Seems we should filter init out in bpf_send_signal_common() by
is_global_init(current), or maybe we should check this in the
verifier?

This can be reproduced on:

HEAD commit: 59fe41b5255f selftests/bpf: Add verifier test exercising jit PROBE_MEM logic
git tree: bpf-next
console output: https://pastebin.com/raw/FMgyvEnH
kernel config : https://pastebin.com/raw/XeF6jU43
C reproducer  : https://pastebin.com/raw/Tag5N893

func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (18) r0 = 0x0                      ; R0_w=0
2: (18) r6 = 0x0                      ; R6_w=0
4: (18) r7 = 0x0                      ; R7_w=0
6: (18) r8 = 0x0                      ; R8_w=0
8: (18) r9 = 0x0                      ; R9_w=0
10: (2d) if r0 > r0 goto pc+2
last_idx 10 first_idx 0
regs=1 stack=0 before 8: (18) r9 = 0x0
regs=1 stack=0 before 6: (18) r8 = 0x0
regs=1 stack=0 before 4: (18) r7 = 0x0
regs=1 stack=0 before 2: (18) r6 = 0x0
regs=1 stack=0 before 0: (18) r0 = 0x0
last_idx 10 first_idx 0
regs=1 stack=0 before 8: (18) r9 = 0x0
regs=1 stack=0 before 6: (18) r8 = 0x0
regs=1 stack=0 before 4: (18) r7 = 0x0
regs=1 stack=0 before 2: (18) r6 = 0x0
regs=1 stack=0 before 0: (18) r0 = 0x0
11: R0_w=0
11: (b7) r1 = 11                      ; R1_w=11
12: (85) call bpf_send_signal_thread#117      ; R0=scalar()
13: (95) exit
processed 9 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 1

Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
CPU: 3 PID: 1 Comm: systemd Not tainted 6.1.0-09652-g59fe41b5255f #148
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
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
RIP: 0033:0x55e738964df0
Code: 00 31 f6 89 ef 4c 8d 05 be 1b 0d 00 48 8d 15 b0 85 0c 00 31 c0 e8 f0 c3 ff ff e9 1c ff ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 <41> 57 41 56 41 55 41 54 41 89 fc 55 53 48 81 ec 48 01 00 00 64 48
RSP: 002b:00007ffeb8e87bb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000f7
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f29dc8a6bc1
RDX: 00007ffeb8e87bc0 RSI: 00007ffeb8e87cf0 RDI: 000000000000000b
RBP: 00007ffeb90b73c0 R08: 0000000000000000 R09: 0000000000000002
R10: 0000000000000004 R11: 0000000000000246 R12: 00007f29dc3f76c8
R13: 000000000000294d R14: 0000000000000000 R15: 00007ffeb9686870
 </TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..