syscalls/sockioctl: Make buf a struct ifreq array

In setup3, the following line can lead to an undefined behavior:
  ifr = *(struct ifreq *)ifc.ifc_buf;

Indeed, at this point it can be assumed that ifc.ifc_buf is suitably
aligned for struct ifreq.
However, ifc.ifc_buf is assigned to buf, a char array, which has no
alignment constraints. This means there exists cases where buf is not
suitably aligned to load a struct ifreq, which can generate a SIGBUS.

Change buf from a char to a struct ifreq array, as it isn't used for
anything else in this test.
This guarantees that buff will be properly aligned.

Reviewed-by: Li Wang <[email protected]>
Reviewed-by: Petr Vorel <[email protected]>
Reviewed-by: Cyril Hrubis <[email protected]>
Signed-off-by: Teo Couprie Diaz <[email protected]>

testcases/kernel/syscalls/sockioctl/sockioctl01.c

@@ -52,7 +52,7 @@ static struct ifreq ifr;
 static int sinlen;
 static int optval;
 
-static char buf[8192];
+static struct ifreq buf[200];
 
 static void setup(void);
 static void setup0(void);
@@ -218,7 +218,7 @@ static void setup2(void)
 	s = SAFE_SOCKET(cleanup, tdat[testno].domain, tdat[testno].type,
 			tdat[testno].proto);
 	ifc.ifc_len = sizeof(buf);
-	ifc.ifc_buf = buf;
+	ifc.ifc_buf = (char *)buf;
 }
 
 static void setup3(void)