[PATCH] ftrace: fix kmemleak in unregister_ftrace_graph

[shuwang]

From: Shu Wang <shuwang@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 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