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

On Wed, Nov 26, 2025 at 09:38:30PM +0530, Ankit Khushwaha wrote:

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

Reviewed-by: Mike Rapoport (Microsoft) rppt@kernel.org

---

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