[PATCH 2/6] libsepol: ensure that hashtab_search is not called with a NULL key

[Nicolas Iooss <nicolas.iooss@xxxxxxx>]

While fuzzing /usr/libexec/hll/pp, a policy module was generated which
triggered a NULL result when doing:

    key = pdb->sym_val_to_name[sym][i];

Detect such unexpected behavior to exit with an error instead of
crashing.

This issue has been found while fuzzing hll/pp with the American Fuzzy
Lop.

Signed-off-by: Nicolas Iooss <nicolas.iooss@xxxxxxx>
---
 libsepol/src/module_to_cil.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libsepol/src/module_to_cil.c b/libsepol/src/module_to_cil.c
index c99790eb76e7..99360a9afdd0 100644
--- a/libsepol/src/module_to_cil.c
+++ b/libsepol/src/module_to_cil.c
@@ -3459,6 +3459,10 @@ static int required_scopes_to_cil(int indent, struct policydb *pdb, struct avrul
 		map = decl->required.scope[sym];
 		ebitmap_for_each_positive_bit(&map, node, i) {
 			key = pdb->sym_val_to_name[sym][i];
+			if (key == NULL) {
+				rc = -1;
+				goto exit;
+			}
 
 			scope_datum = hashtab_search(pdb->scope[sym].table, key);
 			if (scope_datum == NULL) {
-- 
2.29.2