[PATCH v2 0/2] tracing: Fix some bug about synth

[PATCH v2 0/2] tracing: Fix some bug about synth

[Shang XiaoJing]

Some bugs are found when insert synth_event_gen_test, and fixed by this
patch set. 

Shang XiaoJing (2):
  tracing: Fix memory leak in test_gen_synth_cmd() and
    test_empty_synth_event()
  tracing: Fix wild-memory-access in register_synth_event()
---
changes in v2:
- some clean up.
- remove redundant code.
---
 kernel/trace/synth_event_gen_test.c | 16 ++++++----------
 kernel/trace/trace_events_synth.c   |  3 ++-
 2 files changed, 8 insertions(+), 11 deletions(-)

-- 
2.17.1

[PATCH v2 1/2] tracing: Fix memory leak in test_gen_synth_cmd() and test_empty_synth_event()

[Shang XiaoJing]

test_gen_synth_cmd() only free buf in fail path, hence buf will leak
when there is no failure. Add kfree(buf) to prevent the memleak. The
same reason and solution in test_empty_synth_event().

unreferenced object 0xffff8881127de000 (size 2048):
  comm "modprobe", pid 247, jiffies 4294972316 (age 78.756s)
  hex dump (first 32 bytes):
    20 67 65 6e 5f 73 79 6e 74 68 5f 74 65 73 74 20   gen_synth_test
    20 70 69 64 5f 74 20 6e 65 78 74 5f 70 69 64 5f   pid_t next_pid_
  backtrace:
    [<000000004254801a>] kmalloc_trace+0x26/0x100
    [<0000000039eb1cf5>] 0xffffffffa00083cd
    [<000000000e8c3bc8>] 0xffffffffa00086ba
    [<00000000c293d1ea>] do_one_initcall+0xdb/0x480
    [<00000000aa189e6d>] do_init_module+0x1cf/0x680
    [<00000000d513222b>] load_module+0x6a50/0x70a0
    [<000000001fd4d529>] __do_sys_finit_module+0x12f/0x1c0
    [<00000000b36c4c0f>] do_syscall_64+0x3f/0x90
    [<00000000bbf20cf3>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
unreferenced object 0xffff8881127df000 (size 2048):
  comm "modprobe", pid 247, jiffies 4294972324 (age 78.728s)
  hex dump (first 32 bytes):
    20 65 6d 70 74 79 5f 73 79 6e 74 68 5f 74 65 73   empty_synth_tes
    74 20 20 70 69 64 5f 74 20 6e 65 78 74 5f 70 69  t  pid_t next_pi
  backtrace:
    [<000000004254801a>] kmalloc_trace+0x26/0x100
    [<00000000d4db9a3d>] 0xffffffffa0008071
    [<00000000c31354a5>] 0xffffffffa00086ce
    [<00000000c293d1ea>] do_one_initcall+0xdb/0x480
    [<00000000aa189e6d>] do_init_module+0x1cf/0x680
    [<00000000d513222b>] load_module+0x6a50/0x70a0
    [<000000001fd4d529>] __do_sys_finit_module+0x12f/0x1c0
    [<00000000b36c4c0f>] do_syscall_64+0x3f/0x90
    [<00000000bbf20cf3>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 9fe41efaca08 ("tracing: Add synth event generation test module")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
---
changes in v2:
- adjust code for clean.
---
 kernel/trace/synth_event_gen_test.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/synth_event_gen_test.c b/kernel/trace/synth_event_gen_test.c
index 0b15e975d2c2..8d77526892f4 100644
--- a/kernel/trace/synth_event_gen_test.c
+++ b/kernel/trace/synth_event_gen_test.c
@@ -120,15 +120,13 @@ static int __init test_gen_synth_cmd(void)
 
 	/* Now generate a gen_synth_test event */
 	ret = synth_event_trace_array(gen_synth_test, vals, ARRAY_SIZE(vals));
- out:
+ free:
+	kfree(buf);
 	return ret;
  delete:
 	/* We got an error after creating the event, delete it */
 	synth_event_delete("gen_synth_test");
- free:
-	kfree(buf);
-
-	goto out;
+	goto free;
 }
 
 /*
@@ -227,15 +225,13 @@ static int __init test_empty_synth_event(void)
 
 	/* Now trace an empty_synth_test event */
 	ret = synth_event_trace_array(empty_synth_test, vals, ARRAY_SIZE(vals));
- out:
+ free:
+	kfree(buf);
 	return ret;
  delete:
 	/* We got an error after creating the event, delete it */
 	synth_event_delete("empty_synth_test");
- free:
-	kfree(buf);
-
-	goto out;
+	goto free;
 }
 
 static struct synth_field_desc create_synth_test_fields[] = {
-- 
2.17.1

[PATCH v2 2/2] tracing: Fix wild-memory-access in register_synth_event()

[Shang XiaoJing]

In register_synth_event(), if set_synth_event_print_fmt() failed, then
both trace_remove_event_call() and unregister_trace_event() will be
called, which means the trace_event_call will call
__unregister_trace_event() twice. As the result, the second unregister
will causes the wild-memory-access.

register_synth_event
    set_synth_event_print_fmt failed
    trace_remove_event_call
        event_remove
            if call->event.funcs then
            __unregister_trace_event (first call)
    unregister_trace_event
        __unregister_trace_event (second call)

Fix the bug by avoiding to call the second __unregister_trace_event() by
checking if the first one is called.

general protection fault, probably for non-canonical address
	0xfbd59c0000000024: 0000 [#1] SMP KASAN PTI
KASAN: maybe wild-memory-access in range
[0xdead000000000120-0xdead000000000127]
CPU: 0 PID: 3807 Comm: modprobe Not tainted
6.1.0-rc1-00186-g76f33a7eedb4 #299
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:unregister_trace_event+0x6e/0x280
Code: 00 fc ff df 4c 89 ea 48 c1 ea 03 80 3c 02 00 0f 85 0e 02 00 00 48
b8 00 00 00 00 00 fc ff df 4c 8b 63 08 4c 89 e2 48 c1 ea 03 <80> 3c 02
00 0f 85 e2 01 00 00 49 89 2c 24 48 85 ed 74 28 e8 7a 9b
RSP: 0018:ffff88810413f370 EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: ffff888105d050b0 RCX: 0000000000000000
RDX: 1bd5a00000000024 RSI: ffff888119e276e0 RDI: ffffffff835a8b20
RBP: dead000000000100 R08: 0000000000000000 R09: fffffbfff0913481
R10: ffffffff8489a407 R11: fffffbfff0913480 R12: dead000000000122
R13: ffff888105d050b8 R14: 0000000000000000 R15: ffff888105d05028
FS:  00007f7823e8d540(0000) GS:ffff888119e00000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7823e7ebec CR3: 000000010a058002 CR4: 0000000000330ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __create_synth_event+0x1e37/0x1eb0
 create_or_delete_synth_event+0x110/0x250
 synth_event_run_command+0x2f/0x110
 test_gen_synth_cmd+0x170/0x2eb [synth_event_gen_test]
 synth_event_gen_test_init+0x76/0x9bc [synth_event_gen_test]
 do_one_initcall+0xdb/0x480
 do_init_module+0x1cf/0x680
 load_module+0x6a50/0x70a0
 __do_sys_finit_module+0x12f/0x1c0
 do_syscall_64+0x3f/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 4b147936fa50 ("tracing: Add support for 'synthetic' events")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Cc: stable@vger.kernel.org
---
changes in v2:
- remove the redundant if statement.
---
 kernel/trace/trace_events_synth.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index e310052dc83c..63eccc50b492 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -829,8 +829,9 @@ static int register_synth_event(struct synth_event *event)
 
 	ret = set_synth_event_print_fmt(call);
 	if (ret < 0) {
+		/* unregister_trace_event() will be called inside */
 		trace_remove_event_call(call);
-		goto err;
+		return ret;
 	}
  out:
 	return ret;
-- 
2.17.1

Re: [PATCH v2 2/2] tracing: Fix wild-memory-access in register_synth_event()

[Tom Zanussi]

Hi Shang,

On Sun, 2022-11-13 at 15:09 +0800, Shang XiaoJing wrote:
> In register_synth_event(), if set_synth_event_print_fmt() failed,
> then
> both trace_remove_event_call() and unregister_trace_event() will be
> called, which means the trace_event_call will call
> __unregister_trace_event() twice. As the result, the second
> unregister
> will causes the wild-memory-access.
> 
> register_synth_event
>     set_synth_event_print_fmt failed
>     trace_remove_event_call
>         event_remove
>             if call->event.funcs then
>             __unregister_trace_event (first call)
>     unregister_trace_event
>         __unregister_trace_event (second call)
> 
> Fix the bug by avoiding to call the second __unregister_trace_event()
> by
> checking if the first one is called.
> 
> general protection fault, probably for non-canonical address
>         0xfbd59c0000000024: 0000 [#1] SMP KASAN PTI
> KASAN: maybe wild-memory-access in range
> [0xdead000000000120-0xdead000000000127]
> CPU: 0 PID: 3807 Comm: modprobe Not tainted
> 6.1.0-rc1-00186-g76f33a7eedb4 #299
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> RIP: 0010:unregister_trace_event+0x6e/0x280
> Code: 00 fc ff df 4c 89 ea 48 c1 ea 03 80 3c 02 00 0f 85 0e 02 00 00
> 48
> b8 00 00 00 00 00 fc ff df 4c 8b 63 08 4c 89 e2 48 c1 ea 03 <80> 3c
> 02
> 00 0f 85 e2 01 00 00 49 89 2c 24 48 85 ed 74 28 e8 7a 9b
> RSP: 0018:ffff88810413f370 EFLAGS: 00010a06
> RAX: dffffc0000000000 RBX: ffff888105d050b0 RCX: 0000000000000000
> RDX: 1bd5a00000000024 RSI: ffff888119e276e0 RDI: ffffffff835a8b20
> RBP: dead000000000100 R08: 0000000000000000 R09: fffffbfff0913481
> R10: ffffffff8489a407 R11: fffffbfff0913480 R12: dead000000000122
> R13: ffff888105d050b8 R14: 0000000000000000 R15: ffff888105d05028
> FS:  00007f7823e8d540(0000) GS:ffff888119e00000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f7823e7ebec CR3: 000000010a058002 CR4: 0000000000330ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  __create_synth_event+0x1e37/0x1eb0
>  create_or_delete_synth_event+0x110/0x250
>  synth_event_run_command+0x2f/0x110
>  test_gen_synth_cmd+0x170/0x2eb [synth_event_gen_test]
>  synth_event_gen_test_init+0x76/0x9bc [synth_event_gen_test]
>  do_one_initcall+0xdb/0x480
>  do_init_module+0x1cf/0x680
>  load_module+0x6a50/0x70a0
>  __do_sys_finit_module+0x12f/0x1c0
>  do_syscall_64+0x3f/0x90
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: 4b147936fa50 ("tracing: Add support for 'synthetic' events")
> Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
> Cc: stable@vger.kernel.org
> ---
> changes in v2:
> - remove the redundant if statement.
> ---
>  kernel/trace/trace_events_synth.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events_synth.c
> b/kernel/trace/trace_events_synth.c
> index e310052dc83c..63eccc50b492 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -829,8 +829,9 @@ static int register_synth_event(struct
> synth_event *event)
>  
>         ret = set_synth_event_print_fmt(call);
>         if (ret < 0) {
> +               /* unregister_trace_event() will be called inside */
>                 trace_remove_event_call(call);
> -               goto err;
> +               return ret;

Since 'return ret;' is already the next line below, you can just get
rid of this one.

Thanks,

Tom

>         }
>   out:
>         return ret;