kselftest: arm64: Add a null pointer check

There is a 'malloc' call, which can be unsuccessful.
This patch will add the malloc failure checking
to avoid possible null dereference and give more information
about test fail reasons.

Signed-off-by: Kunwu Chan <[e-mail]>
Reviewed-by: Muhammad Usama Anjum <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[e-mail]>

tools/testing/selftests/arm64/tags/tags_test.c

···
 #include <stdint.h>
 #include <sys/prctl.h>
 #include <sys/utsname.h>
+#include "../../kselftest.h"
 
 #define SHIFT_TAG(tag)		((uint64_t)(tag) << 56)
 #define SET_TAG(ptr, tag)	(((uint64_t)(ptr) & ~SHIFT_TAG(0xff)) | \
···
 	if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == 0)
 		tbi_enabled = 1;
 	ptr = (struct utsname *)malloc(sizeof(*ptr));
+	if (!ptr)
+		ksft_exit_fail_msg("Failed to allocate utsname buffer\n");
+
 	if (tbi_enabled)
 		tag = 0x42;
 	ptr = (struct utsname *)SET_TAG(ptr, tag);