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

From: Masami Hiramatsu
Date: Thu Sep 17 2020 - 23:15:06 EST


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@xxxxxxxxxxx> wrote:

> From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx
> Fixes: 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> ---
> 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@xxxxxxxxxx>