On 2025-03-31, Nam Cao namcao@linutronix.de wrote:
The buffer pointer "line" is not initialized. This pointer is passed to getline().
Ouch.
It can still work if the stack is zero-initialized, because getline() can work with a NULL pointer as buffer.
But this is obviously broken. This bug shows up while running the test on a riscv64 machine.
Fix it by properly initializing the pointer.
Fixes: 15858da53542 ("selftests: coredump: Add stackdump test") Signed-off-by: Nam Cao namcao@linutronix.de
tools/testing/selftests/coredump/stackdump_test.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/testing/selftests/coredump/stackdump_test.c b/tools/testing/selftests/coredump/stackdump_test.c index 137b2364a082..1dc54e128586 100644 --- a/tools/testing/selftests/coredump/stackdump_test.c +++ b/tools/testing/selftests/coredump/stackdump_test.c @@ -100,6 +100,8 @@ TEST_F(coredump, stackdump) FILE *file; pid_t pid;
- line = NULL;
The syntax of getline(3) is quite interesting, since it allocates/reallocates/uses the lineptr as needed and possibly requires the application to free the data. I recommend moving the initialization down to the getline() call and also add the corresponding free().
Something like this:
diff --git a/tools/testing/selftests/coredump/stackdump_test.c b/tools/testing/selftests/coredump/stackdump_test.c index 137b2364a082..c23cf95c3f6d 100644 --- a/tools/testing/selftests/coredump/stackdump_test.c +++ b/tools/testing/selftests/coredump/stackdump_test.c @@ -138,10 +138,12 @@ TEST_F(coredump, stackdump) ASSERT_NE(file, NULL);
/* Step 4: Make sure all stack pointer values are non-zero */ + line = NULL; for (i = 0; -1 != getline(&line, &line_length, file); ++i) { stack = strtoull(line, NULL, 10); ASSERT_NE(stack, 0); } + free(line);
ASSERT_EQ(i, 1 + NUM_THREAD_SPAWN);
Because of how getline() works, technically your patch is good enough. But we should probably excercise more precision in the use of getline() so as to set a good example.
John Ogness