[PATCH] libsepol/cil: do not override previous results of __cil_verify_classperms

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

When __cil_verify_map_class() verifies a classpermission, it calls
__verify_map_perm_classperms() on each item. If the first item reports a
failure and the next one succeeds, the failure is overwritten in
map_args->rc. This is a bug which causes a NULL pointer dereference in
the CIL compiler when compiling the following policy:

    (sid SID)
    (sidorder (SID))

    (class CLASS (PERM1))
    (classorder (CLASS))

    (classpermission CLSPERM)
    (classpermissionset CLSPERM (CLASS (PERM1)))
    (classmap files (CLAMAPxx x))
    (classmapping files CLAMAPxx CLSPERM)

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=30286

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
---
 libsepol/cil/src/cil_verify.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libsepol/cil/src/cil_verify.c b/libsepol/cil/src/cil_verify.c
index 59397f70f2ea..8ad3dc9e114a 100644
--- a/libsepol/cil/src/cil_verify.c
+++ b/libsepol/cil/src/cil_verify.c
@@ -1786,8 +1786,12 @@ static int __verify_map_perm_classperms(__attribute__((unused)) hashtab_key_t k,
 {
 	struct cil_verify_map_args *map_args = args;
 	struct cil_perm *cmp = (struct cil_perm *)d;
+	int rc;
 
-	map_args->rc = __cil_verify_classperms(cmp->classperms, &cmp->datum, &map_args->class->datum, &cmp->datum, CIL_MAP_PERM, 0, 2);
+	rc = __cil_verify_classperms(cmp->classperms, &cmp->datum, &map_args->class->datum, &cmp->datum, CIL_MAP_PERM, 0, 2);
+	if (rc != SEPOL_OK) {
+		map_args->rc = rc;
+	}
 
 	return SEPOL_OK;
 }
-- 
2.32.0