Re: [External] [BUGFIX PATCH] kprobes: Fix to check probe enabled before disarm_kprobe_ftrace()

[Masami Hiramatsu]

Hi Muchun,

On Mon, 31 Aug 2020 23:47:14 +0800
Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:

> On Mon, Aug 31, 2020 at 11:12 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> >
> > Commit 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at
> > kprobe_ftrace_handler") fixed one bug but not completely fixed yet.
> > If we run a kprobe_module.tc of ftracetest, kernel showed a warning
> > as below.
> >
> >
> > # ./ftracetest test.d/kprobe/kprobe_module.tc
> > === Ftrace unit tests ===
> > [1] Kprobe dynamic event - probing module
> > ...
> > [   22.400215] ------------[ cut here ]------------
> > [   22.400962] Failed to disarm kprobe-ftrace at trace_printk_irq_work+0x0/0x7e [trace_printk] (-2)
> > [   22.402139] WARNING: CPU: 7 PID: 200 at kernel/kprobes.c:1091 __disarm_kprobe_ftrace.isra.0+0x7e/0xa0
> > [   22.403358] Modules linked in: trace_printk(-)
> > [   22.404028] CPU: 7 PID: 200 Comm: rmmod Not tainted 5.9.0-rc2+ #66
> > [   22.404870] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014
> > [   22.406139] RIP: 0010:__disarm_kprobe_ftrace.isra.0+0x7e/0xa0
> > [   22.406947] Code: 30 8b 03 eb c9 80 3d e5 09 1f 01 00 75 dc 49 8b 34 24 89 c2 48 c7 c7 a0 c2 05 82 89 45 e4 c6 05 cc 09 1f 01 01 e8 a9 c7 f0 ff <0f> 0b 8b 45 e4 eb b9 89 c6 48 c7 c7 70 c2 05 82 89 45 e4 e8 91 c7
> > [   22.409544] RSP: 0018:ffffc90000237df0 EFLAGS: 00010286
> > [   22.410385] RAX: 0000000000000000 RBX: ffffffff83066024 RCX: 0000000000000000
> > [   22.411434] RDX: 0000000000000001 RSI: ffffffff810de8d3 RDI: ffffffff810de8d3
> > [   22.412687] RBP: ffffc90000237e10 R08: 0000000000000001 R09: 0000000000000001
> > [   22.413762] R10: 0000000000000000 R11: 0000000000000001 R12: ffff88807c478640
> > [   22.414852] R13: ffffffff8235ebc0 R14: ffffffffa00060c0 R15: 0000000000000000
> > [   22.415941] FS:  00000000019d48c0(0000) GS:ffff88807d7c0000(0000) knlGS:0000000000000000
> > [   22.417264] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [   22.418176] CR2: 00000000005bb7e3 CR3: 0000000078f7a000 CR4: 00000000000006a0
> > [   22.419309] Call Trace:
> > [   22.419990]  kill_kprobe+0x94/0x160
> > [   22.420652]  kprobes_module_callback+0x64/0x230
> > [   22.421470]  notifier_call_chain+0x4f/0x70
> > [   22.422184]  blocking_notifier_call_chain+0x49/0x70
> > [   22.422979]  __x64_sys_delete_module+0x1ac/0x240
> > [   22.423733]  do_syscall_64+0x38/0x50
> > [   22.424366]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [   22.425176] RIP: 0033:0x4bb81d
> > [   22.425741] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e0 ff ff ff f7 d8 64 89 01 48
> > [   22.428726] RSP: 002b:00007ffc70fef008 EFLAGS: 00000246 ORIG_RAX: 00000000000000b0
> > [   22.430169] RAX: ffffffffffffffda RBX: 00000000019d48a0 RCX: 00000000004bb81d
> > [   22.431375] RDX: 0000000000000000 RSI: 0000000000000880 RDI: 00007ffc70fef028
> > [   22.432543] RBP: 0000000000000880 R08: 00000000ffffffff R09: 00007ffc70fef320
> > [   22.433692] R10: 0000000000656300 R11: 0000000000000246 R12: 00007ffc70fef028
> > [   22.434635] R13: 0000000000000000 R14: 0000000000000002 R15: 0000000000000000
> > [   22.435682] irq event stamp: 1169
> > [   22.436240] hardirqs last  enabled at (1179): [<ffffffff810df542>] console_unlock+0x422/0x580
> > [   22.437466] hardirqs last disabled at (1188): [<ffffffff810df19b>] console_unlock+0x7b/0x580
> > [   22.438608] softirqs last  enabled at (866): [<ffffffff81c0038e>] __do_softirq+0x38e/0x490
> > [   22.439637] softirqs last disabled at (859): [<ffffffff81a00f42>] asm_call_on_stack+0x12/0x20
> > [   22.440690] ---[ end trace 1e7ce7e1e4567276 ]---
> > [   22.472832] trace_kprobe: This probe might be able to register after target module is loaded. Continue.
> >
> >
> > This is because the kill_kprobe() calls disarm_kprobe_ftrace() even
> > if the given probe is not enabled. In that case, ftrace_set_filter_ip()
> > fails because the given probe point is not registered to ftrace.
> 
> Does the following patch solve this issue?  Thanks.
> 
>   kprobes: Fix kill kprobe which has been marked as gone
>   https://lkml.org/lkml/2020/8/19/1496

No, your patch skips all gone probes, but this one disabled ftrace
probes (not gone yet).

Thank you,

-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>