linux-kernel - Re: [PATCH] ftrace: fix kmemleak in unregister_ftrace

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Date:   Tue, 26 Sep 2017 08:01:26 -0400 (EDT)
From:   Shu Wang <shuwang@...hat.com>
To:     rostedt@...dmis.org, mingo@...hat.com
Cc:     chuhu@...hat.com, liwang@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: fix kmemleak in unregister_ftrace_graph

> From: shuwang@...hat.com
> To: rostedt@...dmis.org, mingo@...hat.com
> Cc: chuhu@...hat.com, liwang@...hat.com, linux-kernel@...r.kernel.org, "Shu Wang" <shuwang@...hat.com>
> Sent: Tuesday, September 12, 2017 10:14:54 AM
> Subject: [PATCH] ftrace: fix kmemleak in unregister_ftrace_graph
> 
> From: Shu Wang <shuwang@...hat.com>
> 
> The trampoline allocated by function tracer was
> overwrite by function_graph tracer, and cause
> memory leak. The save_global_trampoline should
> save previous trampoline in register_ftrace_graph
> and restore it in unregister_ftrace_graph. But
> as it implemented, save_global_trampoline was only
> used in unregister_ftrace_graph as default value 0,
> and overwrite the previous trampoline's value.
> 
> kmmeleak backtrace:
>     kmemleak_vmalloc+0x77/0xc0
>     __vmalloc_node_range+0x1b5/0x2c0
>     module_alloc+0x7c/0xd0
>     arch_ftrace_update_trampoline+0xb5/0x290
>     ftrace_startup+0x78/0x210
>     register_ftrace_function+0x8b/0xd0
>     function_trace_init+0x4f/0x80
>     tracing_set_tracer+0xe6/0x170
>     tracing_set_trace_write+0x90/0xd0
>     __vfs_write+0x37/0x170
>     vfs_write+0xb2/0x1b0
>     SyS_write+0x55/0xc0
>     do_syscall_64+0x67/0x180
>     return_from_SYSCALL_64+0x0/0x6a
> 
> Signed-off-by: Shu Wang <shuwang@...hat.com>
> ---
>  kernel/trace/ftrace.c | 14 --------------
>  1 file changed, 14 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 6abfafd7f173..8319e09e15b9 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4954,9 +4954,6 @@ static char ftrace_graph_buf[FTRACE_FILTER_SIZE]
> __initdata;
>  static char ftrace_graph_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
>  static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
>  
> -static unsigned long save_global_trampoline;
> -static unsigned long save_global_flags;
> -
>  static int __init set_graph_function(char *str)
>  {
>  	strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
> @@ -6808,17 +6805,6 @@ void unregister_ftrace_graph(void)
>  	unregister_pm_notifier(&ftrace_suspend_notifier);
>  	unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
>  
> -#ifdef CONFIG_DYNAMIC_FTRACE
> -	/*
> -	 * Function graph does not allocate the trampoline, but
> -	 * other global_ops do. We need to reset the ALLOC_TRAMP flag
> -	 * if one was used.
> -	 */
> -	global_ops.trampoline = save_global_trampoline;
> -	if (save_global_flags & FTRACE_OPS_FL_ALLOC_TRAMP)
> -		global_ops.flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
> -#endif
> -
>   out:
>  	mutex_unlock(&ftrace_lock);
>  }
> --
> 2.13.5
> 
> 

ping