diff mbox series

[2/2] tracing: kprobe: Fix potential null-ptr-deref on trace_array in kprobe_event_gen_test_exit()

Message ID 20221107071617.21644-3-shangxiaojing@huawei.com
State New
Headers
Series tracing: kprobe: Fix some bug in kprobe_event_gen_test.c |

Commit Message

Shang XiaoJing Nov. 7, 2022, 7:16 a.m. UTC 
  When test_gen_kprobe_cmd() failed after kprobe_event_gen_cmd_end(), it
will goto delete, which will call kprobe_event_delete() and release the
corresponding resource. However, the trace_array in gen_kretprobe_test
will point to the invalid resource. Set gen_kretprobe_test->tr to NULL
after called kprobe_event_delete() and add NULL check when releasing
the module.

BUG: kernel NULL pointer dereference, address: 0000000000000070
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 246 Comm: modprobe Tainted: G        W
6.1.0-rc1-00174-g9522dc5c87da-dirty #248
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:__ftrace_set_clr_event_nolock+0x53/0x1b0
Code: e8 82 26 fc ff 49 8b 1e c7 44 24 0c ea ff ff ff 49 39 de 0f 84 3c
01 00 00 c7 44 24 18 00 00 00 00 e8 61 26 fc ff 48 8b 6b 10 <44> 8b 65
70 4c 8b 6d 18 41 f7 c4 00 02 00 00 75 2f
RSP: 0018:ffffc9000159fe00 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88810971d268 RCX: 0000000000000000
RDX: ffff8881080be600 RSI: ffffffff811b48ff RDI: ffff88810971d058
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: ffffc9000159fe58 R11: 0000000000000001 R12: ffffffffa0001064
R13: ffffffffa000106c R14: ffff88810971d238 R15: 0000000000000000
FS:  00007f89eeff6540(0000) GS:ffff88813b600000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000070 CR3: 000000010599e004 CR4: 0000000000330ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __ftrace_set_clr_event+0x3e/0x60
 trace_array_set_clr_event+0x35/0x50
 ? 0xffffffffa0000000
 kprobe_event_gen_test_exit+0xcd/0x10b [kprobe_event_gen_test]
 __x64_sys_delete_module+0x206/0x380
 ? lockdep_hardirqs_on_prepare+0xd8/0x190
 ? syscall_enter_from_user_mode+0x1c/0x50
 do_syscall_64+0x3f/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f89eeb061b7

Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
---
 kernel/trace/kprobe_event_gen_test.c | 29 +++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

Comments

Masami Hiramatsu (Google) Nov. 7, 2022, 1:38 p.m. UTC | #1 
Hi,

On Mon, 7 Nov 2022 15:16:17 +0800
Shang XiaoJing <shangxiaojing@huawei.com> wrote:

> When test_gen_kprobe_cmd() failed after kprobe_event_gen_cmd_end(), it
> will goto delete, which will call kprobe_event_delete() and release the
> corresponding resource. However, the trace_array in gen_kretprobe_test
> will point to the invalid resource. Set gen_kretprobe_test->tr to NULL
> after called kprobe_event_delete() and add NULL check when releasing
> the module.
> 
> BUG: kernel NULL pointer dereference, address: 0000000000000070
> PGD 0 P4D 0
> Oops: 0000 [#1] SMP PTI
> CPU: 0 PID: 246 Comm: modprobe Tainted: G        W
> 6.1.0-rc1-00174-g9522dc5c87da-dirty #248
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> RIP: 0010:__ftrace_set_clr_event_nolock+0x53/0x1b0
> Code: e8 82 26 fc ff 49 8b 1e c7 44 24 0c ea ff ff ff 49 39 de 0f 84 3c
> 01 00 00 c7 44 24 18 00 00 00 00 e8 61 26 fc ff 48 8b 6b 10 <44> 8b 65
> 70 4c 8b 6d 18 41 f7 c4 00 02 00 00 75 2f
> RSP: 0018:ffffc9000159fe00 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff88810971d268 RCX: 0000000000000000
> RDX: ffff8881080be600 RSI: ffffffff811b48ff RDI: ffff88810971d058
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffc9000159fe58 R11: 0000000000000001 R12: ffffffffa0001064
> R13: ffffffffa000106c R14: ffff88810971d238 R15: 0000000000000000
> FS:  00007f89eeff6540(0000) GS:ffff88813b600000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000070 CR3: 000000010599e004 CR4: 0000000000330ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  __ftrace_set_clr_event+0x3e/0x60
>  trace_array_set_clr_event+0x35/0x50
>  ? 0xffffffffa0000000
>  kprobe_event_gen_test_exit+0xcd/0x10b [kprobe_event_gen_test]
>  __x64_sys_delete_module+0x206/0x380
>  ? lockdep_hardirqs_on_prepare+0xd8/0x190
>  ? syscall_enter_from_user_mode+0x1c/0x50
>  do_syscall_64+0x3f/0x90
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f89eeb061b7
> 
> Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
> Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
> ---
>  kernel/trace/kprobe_event_gen_test.c | 29 +++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
> index 1c98fafcf333..277e21e4a63e 100644
> --- a/kernel/trace/kprobe_event_gen_test.c
> +++ b/kernel/trace/kprobe_event_gen_test.c
> @@ -145,6 +145,8 @@ static int __init test_gen_kprobe_cmd(void)
>   delete:
>  	/* We got an error after creating the event, delete it */
>  	ret = kprobe_event_delete("gen_kprobe_test");
> +	if (trace_event_file_is_valid(gen_kprobe_test))
> +		gen_kprobe_test->tr = NULL;

I think the correct fix should be

	if (trace_event_file_is_valid(gen_kprobe_test)) {
		trace_put_event_file(gen_kprobe_test);
		gen_kprobe_test = NULL;
	}
  	ret = kprobe_event_delete("gen_kprobe_test");

Since the gen_kprobe_event is owned by ftrace subsystem, the test
code should not change the tr field.

>  	goto out;
>  }
>  
> @@ -208,6 +210,8 @@ static int __init test_gen_kretprobe_cmd(void)
>   delete:
>  	/* We got an error after creating the event, delete it */
>  	ret = kprobe_event_delete("gen_kretprobe_test");
> +	if (trace_event_file_is_valid(gen_kretprobe_test))
> +		gen_kretprobe_test->tr = NULL;

Ditto.

And then, below changes are not required.

Thank you,

>  	goto out;
>  }
>  
> @@ -222,9 +226,10 @@ static int __init kprobe_event_gen_test_init(void)
>  	ret = test_gen_kretprobe_cmd();
>  	if (ret) {
>  		if (trace_event_file_is_valid(gen_kretprobe_test)) {
> -			WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> -							  "kprobes",
> -							  "gen_kretprobe_test", false));
> +			if (gen_kretprobe_test->tr)
> +				WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> +								  "kprobes",
> +								  "gen_kretprobe_test", false));
>  			trace_put_event_file(gen_kretprobe_test);
>  		}
>  		WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
> @@ -236,10 +241,11 @@ static int __init kprobe_event_gen_test_init(void)
>  static void __exit kprobe_event_gen_test_exit(void)
>  {
>  	if (trace_event_file_is_valid(gen_kprobe_test)) {
> -		/* Disable the event or you can't remove it */
> -		WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
> -						  "kprobes",
> -						  "gen_kprobe_test", false));
> +		if (gen_kprobe_test->tr)
> +			/* Disable the event or you can't remove it */
> +			WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
> +							  "kprobes",
> +							  "gen_kprobe_test", false));
>  
>  		/* Now give the file and instance back */
>  		trace_put_event_file(gen_kprobe_test);
> @@ -250,10 +256,11 @@ static void __exit kprobe_event_gen_test_exit(void)
>  	WARN_ON(kprobe_event_delete("gen_kprobe_test"));
>  
>  	if (trace_event_file_is_valid(gen_kretprobe_test)) {
> -		/* Disable the event or you can't remove it */
> -		WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> -						  "kprobes",
> -						  "gen_kretprobe_test", false));
> +		if (gen_kretprobe_test->tr)
> +			/* Disable the event or you can't remove it */
> +			WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> +							  "kprobes",
> +							  "gen_kretprobe_test", false));
>  
>  		/* Now give the file and instance back */
>  		trace_put_event_file(gen_kretprobe_test);
> -- 
> 2.17.1
>
Shang XiaoJing Nov. 7, 2022, 1:47 p.m. UTC | #2 
Hi,

On 2022/11/7 21:38, Masami Hiramatsu (Google) wrote:
> Hi,
> 
> On Mon, 7 Nov 2022 15:16:17 +0800
> Shang XiaoJing <shangxiaojing@huawei.com> wrote:
> 
>> When test_gen_kprobe_cmd() failed after kprobe_event_gen_cmd_end(), it
>> will goto delete, which will call kprobe_event_delete() and release the
>> corresponding resource. However, the trace_array in gen_kretprobe_test
>> will point to the invalid resource. Set gen_kretprobe_test->tr to NULL
>> after called kprobe_event_delete() and add NULL check when releasing
>> the module.
>>
>> BUG: kernel NULL pointer dereference, address: 0000000000000070
>> PGD 0 P4D 0
>> Oops: 0000 [#1] SMP PTI
>> CPU: 0 PID: 246 Comm: modprobe Tainted: G        W
>> 6.1.0-rc1-00174-g9522dc5c87da-dirty #248
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>> rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
>> RIP: 0010:__ftrace_set_clr_event_nolock+0x53/0x1b0
>> Code: e8 82 26 fc ff 49 8b 1e c7 44 24 0c ea ff ff ff 49 39 de 0f 84 3c
>> 01 00 00 c7 44 24 18 00 00 00 00 e8 61 26 fc ff 48 8b 6b 10 <44> 8b 65
>> 70 4c 8b 6d 18 41 f7 c4 00 02 00 00 75 2f
>> RSP: 0018:ffffc9000159fe00 EFLAGS: 00010293
>> RAX: 0000000000000000 RBX: ffff88810971d268 RCX: 0000000000000000
>> RDX: ffff8881080be600 RSI: ffffffff811b48ff RDI: ffff88810971d058
>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
>> R10: ffffc9000159fe58 R11: 0000000000000001 R12: ffffffffa0001064
>> R13: ffffffffa000106c R14: ffff88810971d238 R15: 0000000000000000
>> FS:  00007f89eeff6540(0000) GS:ffff88813b600000(0000)
>> knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000070 CR3: 000000010599e004 CR4: 0000000000330ef0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>   <TASK>
>>   __ftrace_set_clr_event+0x3e/0x60
>>   trace_array_set_clr_event+0x35/0x50
>>   ? 0xffffffffa0000000
>>   kprobe_event_gen_test_exit+0xcd/0x10b [kprobe_event_gen_test]
>>   __x64_sys_delete_module+0x206/0x380
>>   ? lockdep_hardirqs_on_prepare+0xd8/0x190
>>   ? syscall_enter_from_user_mode+0x1c/0x50
>>   do_syscall_64+0x3f/0x90
>>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> RIP: 0033:0x7f89eeb061b7
>>
>> Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
>> Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
>> ---
>>   kernel/trace/kprobe_event_gen_test.c | 29 +++++++++++++++++-----------
>>   1 file changed, 18 insertions(+), 11 deletions(-)
>>
>> diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
>> index 1c98fafcf333..277e21e4a63e 100644
>> --- a/kernel/trace/kprobe_event_gen_test.c
>> +++ b/kernel/trace/kprobe_event_gen_test.c
>> @@ -145,6 +145,8 @@ static int __init test_gen_kprobe_cmd(void)
>>    delete:
>>   	/* We got an error after creating the event, delete it */
>>   	ret = kprobe_event_delete("gen_kprobe_test");
>> +	if (trace_event_file_is_valid(gen_kprobe_test))
>> +		gen_kprobe_test->tr = NULL;
> 
> I think the correct fix should be
> 
> 	if (trace_event_file_is_valid(gen_kprobe_test)) {
> 		trace_put_event_file(gen_kprobe_test);
> 		gen_kprobe_test = NULL;
> 	}
>    	ret = kprobe_event_delete("gen_kprobe_test");
> 
> Since the gen_kprobe_event is owned by ftrace subsystem, the test
> code should not change the tr field.
> 
When trace_array_set_clr_event() failed, it already called 
trace_put_event_file(), maybe we only need set gen_kprobe_test to NULL.

>>   	goto out;
>>   }
>>   
>> @@ -208,6 +210,8 @@ static int __init test_gen_kretprobe_cmd(void)
>>    delete:
>>   	/* We got an error after creating the event, delete it */
>>   	ret = kprobe_event_delete("gen_kretprobe_test");
>> +	if (trace_event_file_is_valid(gen_kretprobe_test))
>> +		gen_kretprobe_test->tr = NULL;
> 
> Ditto. >
> And then, below changes are not required.

Yes, will fix in v2, thanks for the review.

Thanks,
Masami Hiramatsu (Google) Nov. 7, 2022, 2:50 p.m. UTC | #3 
On Mon, 7 Nov 2022 21:47:10 +0800
shangxiaojing <shangxiaojing@huawei.com> wrote:

> Hi,
> 
> On 2022/11/7 21:38, Masami Hiramatsu (Google) wrote:
> > Hi,
> > 
> > On Mon, 7 Nov 2022 15:16:17 +0800
> > Shang XiaoJing <shangxiaojing@huawei.com> wrote:
> > 
> >> When test_gen_kprobe_cmd() failed after kprobe_event_gen_cmd_end(), it
> >> will goto delete, which will call kprobe_event_delete() and release the
> >> corresponding resource. However, the trace_array in gen_kretprobe_test
> >> will point to the invalid resource. Set gen_kretprobe_test->tr to NULL
> >> after called kprobe_event_delete() and add NULL check when releasing
> >> the module.
> >>
> >> BUG: kernel NULL pointer dereference, address: 0000000000000070
> >> PGD 0 P4D 0
> >> Oops: 0000 [#1] SMP PTI
> >> CPU: 0 PID: 246 Comm: modprobe Tainted: G        W
> >> 6.1.0-rc1-00174-g9522dc5c87da-dirty #248
> >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> >> rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> >> RIP: 0010:__ftrace_set_clr_event_nolock+0x53/0x1b0
> >> Code: e8 82 26 fc ff 49 8b 1e c7 44 24 0c ea ff ff ff 49 39 de 0f 84 3c
> >> 01 00 00 c7 44 24 18 00 00 00 00 e8 61 26 fc ff 48 8b 6b 10 <44> 8b 65
> >> 70 4c 8b 6d 18 41 f7 c4 00 02 00 00 75 2f
> >> RSP: 0018:ffffc9000159fe00 EFLAGS: 00010293
> >> RAX: 0000000000000000 RBX: ffff88810971d268 RCX: 0000000000000000
> >> RDX: ffff8881080be600 RSI: ffffffff811b48ff RDI: ffff88810971d058
> >> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
> >> R10: ffffc9000159fe58 R11: 0000000000000001 R12: ffffffffa0001064
> >> R13: ffffffffa000106c R14: ffff88810971d238 R15: 0000000000000000
> >> FS:  00007f89eeff6540(0000) GS:ffff88813b600000(0000)
> >> knlGS:0000000000000000
> >> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> CR2: 0000000000000070 CR3: 000000010599e004 CR4: 0000000000330ef0
> >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >> Call Trace:
> >>   <TASK>
> >>   __ftrace_set_clr_event+0x3e/0x60
> >>   trace_array_set_clr_event+0x35/0x50
> >>   ? 0xffffffffa0000000
> >>   kprobe_event_gen_test_exit+0xcd/0x10b [kprobe_event_gen_test]
> >>   __x64_sys_delete_module+0x206/0x380
> >>   ? lockdep_hardirqs_on_prepare+0xd8/0x190
> >>   ? syscall_enter_from_user_mode+0x1c/0x50
> >>   do_syscall_64+0x3f/0x90
> >>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> >> RIP: 0033:0x7f89eeb061b7
> >>
> >> Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
> >> Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
> >> ---
> >>   kernel/trace/kprobe_event_gen_test.c | 29 +++++++++++++++++-----------
> >>   1 file changed, 18 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
> >> index 1c98fafcf333..277e21e4a63e 100644
> >> --- a/kernel/trace/kprobe_event_gen_test.c
> >> +++ b/kernel/trace/kprobe_event_gen_test.c
> >> @@ -145,6 +145,8 @@ static int __init test_gen_kprobe_cmd(void)
> >>    delete:
> >>   	/* We got an error after creating the event, delete it */
> >>   	ret = kprobe_event_delete("gen_kprobe_test");
> >> +	if (trace_event_file_is_valid(gen_kprobe_test))
> >> +		gen_kprobe_test->tr = NULL;
> > 
> > I think the correct fix should be
> > 
> > 	if (trace_event_file_is_valid(gen_kprobe_test)) {
> > 		trace_put_event_file(gen_kprobe_test);
> > 		gen_kprobe_test = NULL;
> > 	}
> >    	ret = kprobe_event_delete("gen_kprobe_test");
> > 
> > Since the gen_kprobe_event is owned by ftrace subsystem, the test
> > code should not change the tr field.
> > 
> When trace_array_set_clr_event() failed, it already called 
> trace_put_event_file(), maybe we only need set gen_kprobe_test to NULL.

Ah, OK. That should work.

Thank you,

> 
> >>   	goto out;
> >>   }
> >>   
> >> @@ -208,6 +210,8 @@ static int __init test_gen_kretprobe_cmd(void)
> >>    delete:
> >>   	/* We got an error after creating the event, delete it */
> >>   	ret = kprobe_event_delete("gen_kretprobe_test");
> >> +	if (trace_event_file_is_valid(gen_kretprobe_test))
> >> +		gen_kretprobe_test->tr = NULL;
> > 
> > Ditto. >
> > And then, below changes are not required.
> 
> Yes, will fix in v2, thanks for the review.
> 
> Thanks,
> -- 
> Shang XiaoJing
diff mbox series

Patch

diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
index 1c98fafcf333..277e21e4a63e 100644
--- a/kernel/trace/kprobe_event_gen_test.c
+++ b/kernel/trace/kprobe_event_gen_test.c
@@ -145,6 +145,8 @@  static int __init test_gen_kprobe_cmd(void)
  delete:
 	/* We got an error after creating the event, delete it */
 	ret = kprobe_event_delete("gen_kprobe_test");
+	if (trace_event_file_is_valid(gen_kprobe_test))
+		gen_kprobe_test->tr = NULL;
 	goto out;
 }
 
@@ -208,6 +210,8 @@  static int __init test_gen_kretprobe_cmd(void)
  delete:
 	/* We got an error after creating the event, delete it */
 	ret = kprobe_event_delete("gen_kretprobe_test");
+	if (trace_event_file_is_valid(gen_kretprobe_test))
+		gen_kretprobe_test->tr = NULL;
 	goto out;
 }
 
@@ -222,9 +226,10 @@  static int __init kprobe_event_gen_test_init(void)
 	ret = test_gen_kretprobe_cmd();
 	if (ret) {
 		if (trace_event_file_is_valid(gen_kretprobe_test)) {
-			WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
-							  "kprobes",
-							  "gen_kretprobe_test", false));
+			if (gen_kretprobe_test->tr)
+				WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
+								  "kprobes",
+								  "gen_kretprobe_test", false));
 			trace_put_event_file(gen_kretprobe_test);
 		}
 		WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
@@ -236,10 +241,11 @@  static int __init kprobe_event_gen_test_init(void)
 static void __exit kprobe_event_gen_test_exit(void)
 {
 	if (trace_event_file_is_valid(gen_kprobe_test)) {
-		/* Disable the event or you can't remove it */
-		WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
-						  "kprobes",
-						  "gen_kprobe_test", false));
+		if (gen_kprobe_test->tr)
+			/* Disable the event or you can't remove it */
+			WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
+							  "kprobes",
+							  "gen_kprobe_test", false));
 
 		/* Now give the file and instance back */
 		trace_put_event_file(gen_kprobe_test);
@@ -250,10 +256,11 @@  static void __exit kprobe_event_gen_test_exit(void)
 	WARN_ON(kprobe_event_delete("gen_kprobe_test"));
 
 	if (trace_event_file_is_valid(gen_kretprobe_test)) {
-		/* Disable the event or you can't remove it */
-		WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
-						  "kprobes",
-						  "gen_kretprobe_test", false));
+		if (gen_kretprobe_test->tr)
+			/* Disable the event or you can't remove it */
+			WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
+							  "kprobes",
+							  "gen_kretprobe_test", false));
 
 		/* Now give the file and instance back */
 		trace_put_event_file(gen_kretprobe_test);