[PATCH] selftests/mm/uffd: initialize char variable to Null

Ankit Khushwaha
2025-11-26T16:08:52Z

In "uffd-stress.c" & "uffd-unit-tests.c". address of char variable having
garbage value (uninitialized) is passed to 'write' syscall triggers
warning.

uffd-stress.c:246:39: warning: variable 'c' is uninitialized when
passed as a const pointer argument here
[-Wuninitialized-const-pointer]

uffd-unit-tests.c:581:31: warning: variable 'c' is uninitialized
when passed as a const pointer argument here
[-Wuninitialized-const-pointer]

so the fix is to assign char variable to '\0' to prevent writing of
garbage value.

Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
---
this warning is raised with clang version 21.1.5 (Fedora 21.1.5-1.fc43).
---
tools/testing/selftests/mm/uffd-stress.c | 2 +-
tools/testing/selftests/mm/uffd-unit-tests.c | 8 ++++----
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index b51c89e1cd1a..700fbaa18d44 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -241,7 +241,7 @@ static int stress(struct uffd_args *args)
return 1;

for (cpu = 0; cpu < gopts->nr_parallel; cpu++) {
- char c;
+ char c = '\0';
if (bounces & BOUNCE_POLL) {
if (write(gopts->pipefd[cpu*2+1], &c, 1) != 1)
err("pipefd write error");
diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index f917b4c4c943..f4807242c5b2 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -543,7 +543,7 @@ static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_col
{
unsigned long p;
pthread_t uffd_mon;
- char c;
+ char c = '\0';
struct uffd_args args = { 0 };
args.gopts = gopts;

@@ -759,7 +759,7 @@ static void uffd_sigbus_test_common(uffd_global_test_opts_t *gopts, bool wp)
pthread_t uffd_mon;
pid_t pid;
int err;
- char c;
+ char c = '\0';
struct uffd_args args = { 0 };
args.gopts = gopts;

@@ -819,7 +819,7 @@ static void uffd_events_test_common(uffd_global_test_opts_t *gopts, bool wp)
pthread_t uffd_mon;
pid_t pid;
int err;
- char c;
+ char c = '\0';
struct uffd_args args = { 0 };
args.gopts = gopts;

@@ -1125,7 +1125,7 @@ uffd_move_test_common(uffd_global_test_opts_t *gopts,
{
unsigned long nr;
pthread_t uffd_mon;
- char c;
+ char c = '\0';
unsigned long long count;
struct uffd_args args = { 0 };
char *orig_area_src = NULL, *orig_area_dst = NULL;
--
2.52.0