[PATCH 6.18 255/396] selftests/mm: fix potential wild pointer access of getline due to missing init

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Gellermann <[email protected]>

commit 9f1d75a4ce04095afdb63d8e540092ff8151dacf upstream.

This is another occurrence of using getline where the code assumes that
getline allocates memory to store the line, but the pointer passed to it
is uninitialized and potentially a non-null pointer.  This violates the
Open Group Spec[1] and caused a segfault in a similar situation in
selftest/clone3/clone3_set_tid.  Fix it by initializing the line pointer
to NULL.

The issue has been found by simply grepping through the selftest code
after running into the issue in clone3_set_tid.  Whether it segfaults in
its current state is unknown to me.  But it's good to be addressed due to
defensive reasons.

Link: https://lore.kernel.org/[email protected]
Link: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getline.html [1]
Fixes: 26b4224d9961 ("selftests: expanding more mlock selftest")
Signed-off-by: Chris Gellermann <[email protected]>
Acked-by: David Hildenbrand (arm) <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 tools/testing/selftests/mm/mlock-random-test.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/mlock-random-test.c
+++ b/tools/testing/selftests/mm/mlock-random-test.c
@@ -84,7 +84,7 @@ int get_proc_locked_vm_size(void)
 int get_proc_page_size(unsigned long addr)
 {
 	FILE *smaps;
-	char *line;
+	char *line = NULL;
 	unsigned long mmupage_size = 0;
 	size_t size;