linux-kernel - Re: [PATCH] tracing: kprobe: Fix memory leak in test_gen_kprobe/kretprobe

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Date:   Thu, 3 Nov 2022 11:04:36 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Shang XiaoJing <shangxiaojing@...wei.com>
Cc:     <rostedt@...dmis.org>, <zanussi@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: kprobe: Fix memory leak in
 test_gen_kprobe/kretprobe_cmd()

On Wed, 2 Nov 2022 15:29:54 +0800
Shang XiaoJing <shangxiaojing@...wei.com> wrote:

> test_gen_kprobe_cmd() only free buf in fail path, hence buf will leak
> when there is no failure. Move kfree(buf) from fail path to common path
> to prevent the memleak. The same reason and solution in
> test_gen_kretprobe_cmd().
> 
> unreferenced object 0xffff888143b14000 (size 2048):
>   comm "insmod", pid 52490, jiffies 4301890980 (age 40.553s)
>   hex dump (first 32 bytes):
>     70 3a 6b 70 72 6f 62 65 73 2f 67 65 6e 5f 6b 70  p:kprobes/gen_kp
>     72 6f 62 65 5f 74 65 73 74 20 64 6f 5f 73 79 73  robe_test do_sys
>   backtrace:
>     [<000000006d7b836b>] kmalloc_trace+0x27/0xa0
>     [<0000000009528b5b>] 0xffffffffa059006f
>     [<000000008408b580>] do_one_initcall+0x87/0x2a0
>     [<00000000c4980a7e>] do_init_module+0xdf/0x320
>     [<00000000d775aad0>] load_module+0x3006/0x3390
>     [<00000000e9a74b80>] __do_sys_finit_module+0x113/0x1b0
>     [<000000003726480d>] do_syscall_64+0x35/0x80
>     [<000000003441e93b>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
> 

Good catch!

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thank you!

> Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
> Signed-off-by: Shang XiaoJing <shangxiaojing@...wei.com>
> ---
>  kernel/trace/kprobe_event_gen_test.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
> index 80e04a1e1977..d81f7c51025c 100644
> --- a/kernel/trace/kprobe_event_gen_test.c
> +++ b/kernel/trace/kprobe_event_gen_test.c
> @@ -100,20 +100,20 @@ static int __init test_gen_kprobe_cmd(void)
>  					 KPROBE_GEN_TEST_FUNC,
>  					 KPROBE_GEN_TEST_ARG0, KPROBE_GEN_TEST_ARG1);
>  	if (ret)
> -		goto free;
> +		goto out;
>  
>  	/* Use kprobe_event_add_fields to add the rest of the fields */
>  
>  	ret = kprobe_event_add_fields(&cmd, KPROBE_GEN_TEST_ARG2, KPROBE_GEN_TEST_ARG3);
>  	if (ret)
> -		goto free;
> +		goto out;
>  
>  	/*
>  	 * This actually creates the event.
>  	 */
>  	ret = kprobe_event_gen_cmd_end(&cmd);
>  	if (ret)
> -		goto free;
> +		goto out;
>  
>  	/*
>  	 * Now get the gen_kprobe_test event file.  We need to prevent
> @@ -136,13 +136,11 @@ static int __init test_gen_kprobe_cmd(void)
>  		goto delete;
>  	}
>   out:
> +	kfree(buf);
>  	return ret;
>   delete:
>  	/* We got an error after creating the event, delete it */
>  	ret = kprobe_event_delete("gen_kprobe_test");
> - free:
> -	kfree(buf);
> -
>  	goto out;
>  }
>  
> @@ -170,14 +168,14 @@ static int __init test_gen_kretprobe_cmd(void)
>  					    KPROBE_GEN_TEST_FUNC,
>  					    "$retval");
>  	if (ret)
> -		goto free;
> +		goto out;
>  
>  	/*
>  	 * This actually creates the event.
>  	 */
>  	ret = kretprobe_event_gen_cmd_end(&cmd);
>  	if (ret)
> -		goto free;
> +		goto out;
>  
>  	/*
>  	 * Now get the gen_kretprobe_test event file.  We need to
> @@ -201,13 +199,11 @@ static int __init test_gen_kretprobe_cmd(void)
>  		goto delete;
>  	}
>   out:
> +	kfree(buf);
>  	return ret;
>   delete:
>  	/* We got an error after creating the event, delete it */
>  	ret = kprobe_event_delete("gen_kretprobe_test");
> - free:
> -	kfree(buf);
> -
>  	goto out;
>  }
>  
> -- 
> 2.17.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>