security/apparmor/policy_unpack.c:1212 verify_profile() warn: can 'rules' even be NULL?

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   173ea743bf7a9eef04460e03b00ba267cc52aee2
commit: 1ad22fcc4d0d2fb2e0f35aed555a86d016d5e590 apparmor: rework profile->rules to be a list
config: i386-randconfig-m021-20230424 (https://download.01.org/0day-ci/archive/20230425/202304252318.ote3mtCz-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <error27@xxxxxxxxx>
| Link: https://lore.kernel.org/r/202304252318.ote3mtCz-lkp@xxxxxxxxx/

New smatch warnings:
security/apparmor/policy_unpack.c:1212 verify_profile() warn: can 'rules' even be NULL?

Old smatch warnings:
security/apparmor/policy_unpack.c:175 aa_loaddata_kref() warn: can 'd' even be NULL?
security/apparmor/policy_unpack.c:488 unpack_trans_table() warn: impossible condition '(size > (1 << 24)) => (0-u16max > 16777216)'
security/apparmor/policy_unpack.c:544 unpack_trans_table() error: uninitialized symbol 'table'.
security/apparmor/policy_unpack.c:735 unpack_pdb() warn: unsigned 'policy->size' is never less than zero.
security/apparmor/policy_unpack.c:1081 unpack_profile() warn: passing zero to 'ERR_PTR'

vim +/rules +1212 security/apparmor/policy_unpack.c

736ec752d95e91 John Johansen 2010-07-29  1208  static int verify_profile(struct aa_profile *profile)
736ec752d95e91 John Johansen 2010-07-29  1209  {
1ad22fcc4d0d2f John Johansen 2022-09-05  1210  	struct aa_ruleset *rules = list_first_entry(&profile->rules,
1ad22fcc4d0d2f John Johansen 2022-09-05  1211  						    typeof(*rules), list);
1ad22fcc4d0d2f John Johansen 2022-09-05 @1212  	if (!rules)

It's so weird to see these old warnings show up suddenly...  Anyway,
use list_first_entry_or_null if we expect that the list is empty.
Otherwise, Oops.

1ad22fcc4d0d2f John Johansen 2022-09-05  1213  		return 0;
1ad22fcc4d0d2f John Johansen 2022-09-05  1214  
1ad22fcc4d0d2f John Johansen 2022-09-05  1215  	if ((rules->file.dfa && !verify_dfa_xindex(rules->file.dfa,
1ad22fcc4d0d2f John Johansen 2022-09-05  1216  						  rules->file.trans.size)) ||
1ad22fcc4d0d2f John Johansen 2022-09-05  1217  	    (rules->policy.dfa &&
1ad22fcc4d0d2f John Johansen 2022-09-05  1218  	     !verify_dfa_xindex(rules->policy.dfa, rules->policy.trans.size))) {
7572fea31e3e5c John Johansen 2020-11-13  1219  		audit_iface(profile, NULL, NULL,
7572fea31e3e5c John Johansen 2020-11-13  1220  			    "Unpack: Invalid named transition", NULL, -EPROTO);
736ec752d95e91 John Johansen 2010-07-29  1221  		return -EPROTO;
736ec752d95e91 John Johansen 2010-07-29  1222  	}
736ec752d95e91 John Johansen 2010-07-29  1223  
1ad22fcc4d0d2f John Johansen 2022-09-05  1224  	if (!verify_perms(&rules->file)) {
670f31774ab6bf John Johansen 2022-08-26  1225  		audit_iface(profile, NULL, NULL,
670f31774ab6bf John Johansen 2022-08-26  1226  			    "Unpack: Invalid perm index", NULL, -EPROTO);
670f31774ab6bf John Johansen 2022-08-26  1227  		return -EPROTO;
670f31774ab6bf John Johansen 2022-08-26  1228  	}
1ad22fcc4d0d2f John Johansen 2022-09-05  1229  	if (!verify_perms(&rules->policy)) {
670f31774ab6bf John Johansen 2022-08-26  1230  		audit_iface(profile, NULL, NULL,
670f31774ab6bf John Johansen 2022-08-26  1231  			    "Unpack: Invalid perm index", NULL, -EPROTO);
670f31774ab6bf John Johansen 2022-08-26  1232  		return -EPROTO;
670f31774ab6bf John Johansen 2022-08-26  1233  	}
217af7e2f4deb6 John Johansen 2022-07-29  1234  	if (!verify_perms(&profile->attach.xmatch)) {
670f31774ab6bf John Johansen 2022-08-26  1235  		audit_iface(profile, NULL, NULL,
670f31774ab6bf John Johansen 2022-08-26  1236  			    "Unpack: Invalid perm index", NULL, -EPROTO);
670f31774ab6bf John Johansen 2022-08-26  1237  		return -EPROTO;
670f31774ab6bf John Johansen 2022-08-26  1238  	}
670f31774ab6bf John Johansen 2022-08-26  1239  
736ec752d95e91 John Johansen 2010-07-29  1240  	return 0;
736ec752d95e91 John Johansen 2010-07-29  1241  }

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