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Thu, 24 Nov 2022 01:14:01 +0000 (GMT) Message-ID: <13350b79f708cb089e2ff2ee5cead52bafb10982.camel@linux.ibm.com> Subject: Re: [PATCH v6 4/6] security: Allow all LSMs to provide xattrs for inode_init_security hook From: Mimi Zohar To: Roberto Sassu , mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, dmitry.kasatkin@gmail.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, casey@schaufler-ca.com Cc: ocfs2-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, linux-kernel@vger.kernel.org, keescook@chromium.org, nicolas.bouchinet@clip-os.org, Roberto Sassu Date: Wed, 23 Nov 2022 20:14:01 -0500 In-Reply-To: <20221123154712.752074-5-roberto.sassu@huaweicloud.com> References: <20221123154712.752074-1-roberto.sassu@huaweicloud.com> <20221123154712.752074-5-roberto.sassu@huaweicloud.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: fUsiWD_L9co63XKlkMcookDkMS_RvTrX X-Proofpoint-ORIG-GUID: slNL7hiw8nwoTRLrZnEqIE5i5-tx6EkG X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-11-23_13,2022-11-23_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 malwarescore=0 mlxscore=0 mlxlogscore=999 spamscore=0 phishscore=0 bulkscore=0 suspectscore=0 priorityscore=1501 clxscore=1015 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2211240006 Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Hi Roberto, On Wed, 2022-11-23 at 16:47 +0100, Roberto Sassu wrote: > int security_inode_init_security(struct inode *inode, struct inode *dir, > const struct qstr *qstr, > const initxattrs initxattrs, void *fs_data) > { > - struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1]; > - struct xattr *lsm_xattr, *evm_xattr, *xattr; > - int ret; > + struct security_hook_list *P; > + struct xattr *new_xattrs; > + struct xattr *xattr; > + int ret = -EOPNOTSUPP, num_filled_xattrs = 0; > > if (unlikely(IS_PRIVATE(inode))) > return 0; > > + if (!blob_sizes.lbs_xattr) > + return 0; > + > if (!initxattrs) > return call_int_hook(inode_init_security, -EOPNOTSUPP, inode, > - dir, qstr, NULL, NULL, NULL); > - memset(new_xattrs, 0, sizeof(new_xattrs)); > - lsm_xattr = new_xattrs; > - ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr, > - &lsm_xattr->name, > - &lsm_xattr->value, > - &lsm_xattr->value_len); > - if (ret) > + dir, qstr, NULL); > + /* Allocate +1 for EVM and +1 as terminator. */ > + new_xattrs = kcalloc(blob_sizes.lbs_xattr + 2, sizeof(*new_xattrs), > + GFP_NOFS); > + if (!new_xattrs) > + return -ENOMEM; > + > + hlist_for_each_entry(P, &security_hook_heads.inode_init_security, > + list) { > + ret = P->hook.inode_init_security(inode, dir, qstr, new_xattrs); > + if (ret && ret != -EOPNOTSUPP) > + goto out; > + if (ret == -EOPNOTSUPP) > + continue; In this context, -EOPNOTSUPP originally signified that the filesystem does not support writing xattrs. Writing any xattr would fail. Returning -ENODATA for no LSM xattr(s) data would seem to be more appropriate than -EOPNOTSUPP. thanks, Mimi > + /* > + * As the number of xattrs reserved by LSMs is not directly > + * available, directly use the total number blob_sizes.lbs_xattr > + * to keep the code simple, while being not the most efficient > + * way. > + */ > + ret = security_check_compact_filled_xattrs(new_xattrs, > + blob_sizes.lbs_xattr, > + &num_filled_xattrs); > + if (ret < 0) { > + ret = -ENOMEM; > + goto out; > + } > + } > + > + if (!num_filled_xattrs) > goto out; > > - evm_xattr = lsm_xattr + 1; > - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr); > + ret = evm_inode_init_security(inode, new_xattrs, > + new_xattrs + num_filled_xattrs); > if (ret) > goto out; > ret = initxattrs(inode, new_xattrs, fs_data); > out: > for (xattr = new_xattrs; xattr->value != NULL; xattr++) > kfree(xattr->value); > + kfree(new_xattrs); > return (ret == -EOPNOTSUPP) ? 0 : ret; > } b