[PATCH] stm class: Fix a double vfree in stm_register_device()

[Qinglang Miao]

While testing stm, stm_register_device() caused a vfree issue:
-----
Trying to vfree() nonexistent vm area (00000000ad30ebb6)

Call Trace:
__vfree+0x41/0xe0
vfree+0x5f/0xa0
stm_register_device+0x4b1/0x660 [stm_core]
dummy_stm_init+0x248/0x360 [dummy_stm]
do_one_initcall+0x149/0x7e0
do_init_module+0x1ef/0x700
load_module+0x3467/0x4140
__do_sys_finit_module+0x10d/0x1a0
do_syscall_64+0x34/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x468ded
-----

This is because put_device(&stm->dev) calls stm_device_release,
which would call vfree(stm) inside, so there's no need to do
vfree again.

Fix this problem by simply return err after put_device().

Fixes: b5e2ced9bf81 ("stm class: Use vmalloc for the master map")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Qinglang Miao <miaoqinglang@xxxxxxxxxx>
---
 drivers/hwtracing/stm/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 2712e699b..80b7c81d5 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -915,6 +915,8 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 
 	/* matches device_initialize() above */
 	put_device(&stm->dev);
+
+	return err;
 err_free:
 	vfree(stm);
 
-- 
2.23.0