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Subject[PATCH 1/2] ftrace: Fix kmemleak in unregister_ftrace_graph
From: Shu Wang <shuwang@redhat.com>

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 5f151b2401 ("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: 5f151b2401 ("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>
---
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);
}
--
2.13.2

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