[PATCH] selftests/mm: check strdup() and fix buf leak in parse_test_type()

[Anshuman <anshumantewari123@gmail.com>]

The return value of strdup() is never checked before being passed to
strsep() and strcmp(). If strdup() fails and returns NULL, strsep()
returns NULL as well, and the subsequent strcmp(NULL, "all") is
undefined behavior, likely causing a crash.

Additionally, buf is never freed. strsep() advances the buf pointer
past the first token, so by the time buf would normally be freed,
the original pointer returned by strdup() has already been
overwritten and is no longer available.

Check strdup()'s return value and fail cleanly on allocation failure.
Keep a separate pointer to the original allocation so it can be
freed once buf is done being used, after all parsing has completed
successfully.

Signed-off-by: Anshuman <anshumantewari123@gmail.com>
---
 tools/testing/selftests/mm/khugepaged.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
index 10e8dedcb..a84fb87bd 100644
--- a/tools/testing/selftests/mm/khugepaged.c
+++ b/tools/testing/selftests/mm/khugepaged.c
@@ -1110,6 +1110,7 @@ static void parse_test_type(int argc, char **argv)
 {
 	int opt;
 	char *buf;
+	char *c;
 	const char *token;
 
 	while ((opt = getopt(argc, argv, "s:h")) != -1) {
@@ -1135,7 +1136,10 @@ static void parse_test_type(int argc, char **argv)
 	}
 
 	buf = strdup(argv[0]);
-	token = strsep(&buf, ":");
+	if (!buf)
+		ksft_exit_fail_msg("Insufficient memory\n");
+	c = buf;
+	token = strsep(&c, ":");
 
 	if (!strcmp(token, "all")) {
 		khugepaged_context =  &__khugepaged_context;
@@ -1148,26 +1152,27 @@ static void parse_test_type(int argc, char **argv)
 		usage();
 	}
 
-	if (!buf)
+	if (!c)
 		usage();
 
-	if (!strcmp(buf, "all")) {
+	if (!strcmp(c, "all")) {
 		read_only_file_ops =  &__read_only_file_ops;
 		read_write_file_read_ops =  &__read_write_file_read_ops;
 		read_write_file_write_ops =  &__read_write_file_write_ops;
 		anon_ops = &__anon_ops;
 		shmem_ops = &__shmem_ops;
-	} else if (!strcmp(buf, "anon")) {
+	} else if (!strcmp(c, "anon")) {
 		anon_ops = &__anon_ops;
-	} else if (!strcmp(buf, "file")) {
+	} else if (!strcmp(c, "file")) {
 		read_only_file_ops =  &__read_only_file_ops;
 		read_write_file_read_ops =  &__read_write_file_read_ops;
 		read_write_file_write_ops =  &__read_write_file_write_ops;
-	} else if (!strcmp(buf, "shmem")) {
+	} else if (!strcmp(c, "shmem")) {
 		shmem_ops = &__shmem_ops;
 	} else {
 		usage();
 	}
+	free(buf);
 
 	if (!read_only_file_ops && !read_write_file_read_ops &&
 	    !read_write_file_write_ops)
-- 
2.55.0