tracing: kprobe: Fix memory leak in test_gen_kprobe/kretprobe_cmd()

stable inclusion
from stable-v5.10.154
commit bef08acbe560a926b4cee9cc46404cc98ae5703b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I64YCB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bef08acbe560a926b4cee9cc46404cc98ae5703b

--------------------------------

commit 66f0919c upstream.

test_gen_kprobe_cmd() only free buf in fail path, hence buf will leak
when there is no failure. Move kfree(buf) from fail path to common path
to prevent the memleak. The same reason and solution in
test_gen_kretprobe_cmd().

unreferenced object 0xffff888143b14000 (size 2048):
  comm "insmod", pid 52490, jiffies 4301890980 (age 40.553s)
  hex dump (first 32 bytes):
    70 3a 6b 70 72 6f 62 65 73 2f 67 65 6e 5f 6b 70  p:kprobes/gen_kp
    72 6f 62 65 5f 74 65 73 74 20 64 6f 5f 73 79 73  robe_test do_sys
  backtrace:
    [<000000006d7b836b>] kmalloc_trace+0x27/0xa0
    [<0000000009528b5b>] 0xffffffffa059006f
    [<000000008408b580>] do_one_initcall+0x87/0x2a0
    [<00000000c4980a7e>] do_init_module+0xdf/0x320
    [<00000000d775aad0>] load_module+0x3006/0x3390
    [<00000000e9a74b80>] __do_sys_finit_module+0x113/0x1b0
    [<000000003726480d>] do_syscall_64+0x35/0x80
    [<000000003441e93b>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

Link: https://lore.kernel.org/all/20221102072954.26555-1-shangxiaojing@huawei.com/



Fixes: 64836248 ("tracing: Add kprobe event command generation test module")
Cc: stable@vger.kernel.org
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lipeng Sang <sanglipeng1@jd.com>