[LTP] [PATCH] syscalls/semctl03: Solve kernel panic in semctl03

[Dylan Jhong]

When using semctl() through glibc and __IPC_TIME64 is defined, glibc will
call a converted semun64_to_ksemun64() function[*1]. If the parameter of
this function is NULL, it will cause a NULL pointer dereference kernel
panic.

In semctl03.c, we need to ensure the element "struct semid_ds *buf" in 4th
parameter "union semun" in semctl() is not NULL. But the 4th parameters of
libc_semctl() and sys_semctl() are hard-coded[*2] and the element
"struct semid_ds *buf" is not given an initial value. Using va_list to pass
the correct parameters can solve the problem.

ref:
  [*1]: https://github.com/bminor/glibc/blob/f94f6d8a3572840d3ba42ab9ace3ea522c99c0c2/sysdeps/unix/sysv/linux/semctl.c#L172
  [*2]: https://github.com/linux-test-project/ltp/blob/58caa8cca507133ea92bd0ea277b91add96e72af/testcases/kernel/syscalls/ipc/semctl/semctl03.c#L45

Co-developed-by: Randolph <randolph@andestech.com>
Signed-off-by: Dylan Jhong <dylan@andestech.com>
---
 testcases/kernel/syscalls/ipc/semctl/semctl03.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/testcases/kernel/syscalls/ipc/semctl/semctl03.c b/testcases/kernel/syscalls/ipc/semctl/semctl03.c
index a1a4c81ce..bb25053e2 100644
--- a/testcases/kernel/syscalls/ipc/semctl/semctl03.c
+++ b/testcases/kernel/syscalls/ipc/semctl/semctl03.c
@@ -28,11 +28,21 @@ static union semun arg = {0};
 
 static int libc_semctl(int semid, int semnum, int cmd, ...)
 {
+	va_list ap;
+
+	va_start(ap, cmd);
+	arg = va_arg(ap, union semun);
+	va_end(ap);
 	return semctl(semid, semnum, cmd, arg);
 }
 
 static int sys_semctl(int semid, int semnum, int cmd, ...)
 {
+	va_list ap;
+
+	va_start(ap, cmd);
+	arg = va_arg(ap, union semun);
+	va_end(ap);
 	return tst_syscall(__NR_semctl, semid, semnum, cmd, arg);
 }
 
-- 
2.34.1