[PATCH 1/1] libsepol/cil: silence static analyser's use-after-free warning

[Nicolas Iooss <nicolas.iooss@m4x.org>]

clang's static analyze reports a use-after-free in
__cil_expr_to_string(), when __cil_expr_to_string_helper() does not
modify its third parameter (variable s1 here) in this loop:

    for (curr = curr->next; curr; curr = curr->next) {
        __cil_expr_to_string_helper(curr, flavor, &s1);
        cil_asprintf(&c2, "%s %s", c1, s1);
        free(c1);
        free(s1);
        c1 = c2;
    }

Silence this warning by making sure s1 is always NULL at the beginning
of every iteration of the loop.

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
---
 libsepol/cil/src/cil_binary.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libsepol/cil/src/cil_binary.c b/libsepol/cil/src/cil_binary.c
index a10c3763bea4..e2eb3ebe8ff3 100644
--- a/libsepol/cil/src/cil_binary.c
+++ b/libsepol/cil/src/cil_binary.c
@@ -2075,6 +2075,7 @@ static void __cil_expr_to_string(struct cil_list *expr, enum cil_flavor flavor,
 		char *c2 = NULL;
 		__cil_expr_to_string_helper(curr, flavor, &c1);
 		for (curr = curr->next; curr; curr = curr->next) {
+			s1 = NULL;
 			__cil_expr_to_string_helper(curr, flavor, &s1);
 			cil_asprintf(&c2, "%s %s", c1, s1);
 			free(c1);
-- 
2.20.1