From: Mimi Zohar <zohar@linux.ibm.com>
To: Casey Schaufler <casey@schaufler-ca.com>,
Roberto Sassu <roberto.sassu@huaweicloud.com>,
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
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 <roberto.sassu@huawei.com>
Subject: Re: [PATCH v6 4/6] security: Allow all LSMs to provide xattrs for inode_init_security hook
Date: Wed, 30 Nov 2022 16:23:43 -0500 [thread overview]
Message-ID: <b929e0c597161fd5be79c18163a11649dd7f237f.camel@linux.ibm.com> (raw)
In-Reply-To: <50232f2b-d5ce-1e5a-3f5b-8d3eb53fe1ec@schaufler-ca.com>
On Tue, 2022-11-29 at 07:39 -0800, Casey Schaufler wrote:
> On 11/29/2022 3:23 AM, Mimi Zohar wrote:
> > On Thu, 2022-11-24 at 09:17 +0100, Roberto Sassu wrote:
> >> On Wed, 2022-11-23 at 20:14 -0500, Mimi Zohar wrote:
> >>> 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.
> >> Hi Mimi
> >>
> >> I thought about adding new return values. Currently only -EOPNOTSUPP
> >> and -ENOMEM are expected as errors.
> >>
> >> However, changing the conventions would mean revisiting the LSMs code
> >> and ensuring that they follow the new conventions.
> >>
> >> I would be more in favor of not touching it.
> > Casey, Paul, any comment?
>
> I don't see value in adding -ENODATA as a value special to
> the infrastructure. What would the infrastructure do differently?
> The use of -EOPNOTSUPP isn't consistent throughout, and the amount
> of "correctness" you get by returning -ENODATA is really small.
Agreed, it isn't worthwhile for this case. Roberto, to ease code
review, could you document the overloading of the -EOPNOTSUPP meaning,
which results in the loop continuing?
thanks,
Mimi
next prev parent reply other threads:[~2022-11-30 21:24 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-23 15:47 [PATCH v6 0/6] evm: Do HMAC of multiple per LSM xattrs for new inodes Roberto Sassu
2022-11-23 15:47 ` [PATCH v6 1/6] reiserfs: Switch to security_inode_init_security() Roberto Sassu
2022-11-23 15:47 ` [PATCH v6 2/6] ocfs2: " Roberto Sassu
2022-11-23 15:47 ` [PATCH v6 3/6] security: Remove security_old_inode_init_security() Roberto Sassu
2022-11-23 15:47 ` [PATCH v6 4/6] security: Allow all LSMs to provide xattrs for inode_init_security hook Roberto Sassu
2022-11-23 17:17 ` Casey Schaufler
2022-11-24 7:55 ` Roberto Sassu
2022-11-24 1:14 ` Mimi Zohar
2022-11-24 8:17 ` Roberto Sassu
2022-11-29 11:23 ` Mimi Zohar
2022-11-29 15:39 ` Casey Schaufler
2022-11-30 21:23 ` Mimi Zohar [this message]
2022-11-23 15:47 ` [PATCH v6 5/6] evm: Align evm_inode_init_security() definition with LSM infrastructure Roberto Sassu
2022-11-23 15:47 ` [PATCH v6 6/6] evm: Support multiple LSMs providing an xattr Roberto Sassu
2022-11-23 16:22 ` [PATCH v6 0/6] evm: Do HMAC of multiple per LSM xattrs for new inodes Mimi Zohar
2022-11-23 17:20 ` Casey Schaufler
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