Commit 2b0b8499 authored Sep 12, 2017 by Shu Wang Committed by Steven Rostedt (VMware) Oct 03, 2017

ftrace: Fix kmemleak in unregister_ftrace_graph

The trampoline allocated by function tracer was overwriten by function_graph
tracer, and caused a memory leak. The save_global_trampoline should have
saved the previous trampoline in register_ftrace_graph() and restored it in
unregister_ftrace_graph(). But as it is implemented, save_global_trampoline was
only used in unregister_ftrace_graph as default value 0, and it overwrote the
previous trampoline's value. Causing the previous allocated trampoline to be
lost.

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

[
  Looking further into this, I found that this was left over from when the
  function and function graph tracers shared the same ftrace_ops. But in
  commit 5f151b24 ("ftrace: Fix function_profiler and function tracer
  together"), the two were separated, and the save_global_trampoline no
  longer was necessary (and it may have been broken back then too).
  -- Steven Rostedt
]

Link: http://lkml.kernel.org/r/20170912021454.5976-1-shuwang@redhat.com



Cc: stable@vger.kernel.org
Fixes: 5f151b24 ("ftrace: Fix function_profiler and function tracer together")
Signed-off-by: Shu Wang <shuwang@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 15516c89

kernel/trace/ftrace.c

+0 −14

Original line number	Diff line number	Diff line
		@@ -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);
		}

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