checkpolicy: free memory on duplicate user declaration

class process
sid tl
class process { transition }
sensitivity s0;
dominance { s0 }
category c0;
level s0;
mlsconstrain process transition t1 eq t2;
role e;
user sys_useallowr roles e level s0 range s0:c0;
user sys_useallowr roles e level s0 range s0;
sid e se:s:s

Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0x5259cd in malloc (./out/checkpolicy-fuzzer+0x5259cd)
    SELinuxProject#1 0x606369 in mls_semantic_level_cpy ./libsepol/src/mls.c:768:30
    SELinuxProject#2 0x57bb08 in define_user ./checkpolicy/policy_define.c:4377:8
    SELinuxProject#3 0x585955 in yyparse ./checkpolicy/policy_parse.y:657:30
    SELinuxProject#4 0x55a7d7 in read_source_policy ./checkpolicy/fuzz/checkpolicy-fuzzer.c:108:6
    SELinuxProject#5 0x55a7d7 in LLVMFuzzerTestOneInput ./checkpolicy/fuzz/checkpolicy-fuzzer.c:162:6
    SELinuxProject#6 0x45af33 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
    SELinuxProject#7 0x446a72 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
    SELinuxProject#8 0x44c99b in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
    SELinuxProject#9 0x475e32 in main (./out/checkpolicy-fuzzer+0x475e32)
    SELinuxProject#10 0x7febb0536e49 in __libc_start_main csu/../csu/libc-start.c:314:16

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

checkpolicy/policy_define.c

@@ -4392,6 +4392,7 @@ int define_user(void)
 		}
 
 		if (l == 0) {
+			mls_semantic_level_destroy(&usrdatum->range.level[1]);
 			if (mls_semantic_level_cpy(&usrdatum->range.level[1],
 			                           &usrdatum->range.level[0])) {
 				yyerror("out of memory");