Re: [PATCH] kprobes: Do not disarm disabled ftrace kprobe

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi Steve,

Ah, this seems to fix same issue which I sent.

https://lkml.kernel.org/r/159888672694.1411785.5987998076694782591.stgit@devnote2

Could you confirm it?

Thank you,

On Thu, 17 Sep 2020 19:17:54 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: Steven Rostedt (VMware) <rostedt@goodmis.org>
> 
> Only disable a ftrace probe if it is enabled, otherwise:
> 
> The following triggers a warning:
> 
>   # modprobe trace_printk
>   # echo "p:kprobes1/event1 trace_printk:trace_printk_irq_work" > /sys/kernel/tracing/kprobe_events
>   # rmmod trace_printk
> 
>  ------------[ cut here ]------------
>  Failed to disarm kprobe-ftrace at trace_printk_irq_work+0x0/0x76 [trace_printk] (-2)
>  WARNING: CPU: 5 PID: 4852 at kernel/kprobes.c:1100 __disarm_kprobe_ftrace.isra.0+0x78/0xa0
>  Modules linked in: trace_printk(-) [..] [last unloaded: trace_printk]
>  CPU: 5 PID: 4852 Comm: rmmod Tainted: G        W         5.9.0-rc4-test+ #506
>  Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
>  RIP: 0010:__disarm_kprobe_ftrace.isra.0+0x78/0xa0
>  Code: 8b 03 eb cb 80 3d 5d 95 58 01 00 75 de 48 8b 75 00 89 c2 89 44 24 04 48 c7 c7 38 e3 33 8b c6 05 43 95 58 01 01 e8 c8 1d ef ff <0f> 0b 8b 44 24 04 eb b9 89 c6 48 c7 c7 08 e3 33 8b 89 44 24 04 e8
>  RSP: 0018:ffff971ce04b7e38 EFLAGS: 00010282
>  RAX: 0000000000000000 RBX: ffffffff8c900b30 RCX: 0000000000000000
>  RDX: 0000000000000001 RSI: ffffffff8a16c5af RDI: ffffffff8a16c5af
>  RBP: ffff971cf2722440 R08: 0000000000000001 R09: 0000000000000001
>  R10: 0000000000000000 R11: 0000000000000046 R12: ffffffff8b7b33a0
>  R13: ffffffff8c901eb0 R14: 0000000000000000 R15: 0000000000000000
>  FS:  00007f4fe349b740(0000) GS:ffff971d5ab40000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 000055d07b0148b8 CR3: 00000000b76cc006 CR4: 00000000001706e0
>  Call Trace:
>   kprobes_module_callback+0x1b3/0x3c0
>   notifier_call_chain+0x47/0x70
>   blocking_notifier_call_chain+0x43/0x60
>   __x64_sys_delete_module+0x161/0x2a0
>   do_syscall_64+0x33/0x40
>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  RIP: 0033:0x7f4fe35cb00b
>  Code: 73 01 c3 48 8b 0d 7d fe 0b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 4d fe 0b 00 f7 d8 64 89 01 48
>  RSP: 002b:00007ffe820f9888 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
>  RAX: ffffffffffffffda RBX: 000055d07b00a800 RCX: 00007f4fe35cb00b
>  RDX: 000000000000000a RSI: 0000000000000800 RDI: 000055d07b00a868
>  RBP: 00007ffe820f98e8 R08: 0000000000000000 R09: 0000000000000000
>  R10: 00007f4fe363eac0 R11: 0000000000000206 R12: 00007ffe820f9ab0
>  R13: 00007ffe820fb223 R14: 000055d07b00a2a0 R15: 000055d07b00a800
>  irq event stamp: 7463
>  hardirqs last  enabled at (7489): [<ffffffff8a1ab4cd>] __tick_nohz_task_switch+0xad/0xc0
>  hardirqs last disabled at (7510): [<ffffffff8a1ab4d4>] __tick_nohz_task_switch+0xb4/0xc0
>  softirqs last  enabled at (7530): [<ffffffff8ae003b4>] __do_softirq+0x3b4/0x501
>  softirqs last disabled at (7545): [<ffffffff8ac01072>] asm_call_on_stack+0x12/0x20
>  ---[ end trace 71f3303cdebb63e3 ]---
> 
> As well as the following two ftrace selftests fail:
> 
>  test.d/kprobe/kprobe_module.tc
>  test.d/kprobe/kretprobe_args.tc
> 
> This is because we are trying to remove a probe that is not enabled or
> registered with ftrace, but exists in the kprobe tables.
> 
> Cc: stable@vger.kernel.org
> Fixes: 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 287b263c9cb9..7557883771f9 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1088,6 +1088,9 @@ static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
>  {
>  	int ret = 0;
>  
> +	if (kprobe_disabled(p))
> +		return ret;
> +
>  	if (*cnt == 1) {
>  		ret = unregister_ftrace_function(ops);
>  		if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))


-- 
Masami Hiramatsu <mhiramat@kernel.org>