From: Mimi Zohar <zohar@linux.ibm.com>
To: 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,
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 <roberto.sassu@huawei.com>
Subject: Re: [PATCH v7 5/6] evm: Align evm_inode_init_security() definition with LSM infrastructure
Date: Sun, 19 Feb 2023 14:41:47 -0500 [thread overview]
Message-ID: <b7b4eeb060d1f662f990b3ebb3848fa4ab7e8c97.camel@linux.ibm.com> (raw)
In-Reply-To: <20221201104125.919483-6-roberto.sassu@huaweicloud.com>
On Thu, 2022-12-01 at 11:41 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Change the evm_inode_init_security() definition to align with the LSM
> infrastructure. Keep the existing behavior of including in the HMAC
> calculation only the first xattr provided by LSMs.
>
> Changing the evm_inode_init_security() definition requires passing only the
> xattr array allocated by security_inode_init_security(), instead of the
> first LSM xattr and the place where the EVM xattr should be filled. In lieu
> of passing the EVM xattr, EVM must position itself after the last filled
> xattr (by checking the xattr name), since only the beginning of the xattr
> array is given.
>
> Finally, make evm_inode_init_security() return value compatible with the
> inode_init_security hook conventions, i.e. return -EOPNOTSUPP if it is not
> setting an xattr.
>
> EVM is a bit tricky, because xattrs is both an input and an output. If it
> was just output, EVM should have returned zero if xattrs is NULL. But,
> since xattrs is also input, EVM is unable to do its calculations, so return
> -EOPNOTSUPP and handle this error in security_inode_init_security().
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
One comment below, otherwise,
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
> include/linux/evm.h | 12 ++++++------
> security/integrity/evm/evm_main.c | 20 +++++++++++++-------
> security/security.c | 5 ++---
> 3 files changed, 21 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/evm.h b/include/linux/evm.h
> index aa63e0b3c0a2..3bb2ae9fe098 100644
> --- a/include/linux/evm.h
> +++ b/include/linux/evm.h
> @@ -35,9 +35,9 @@ extern int evm_inode_removexattr(struct user_namespace *mnt_userns,
> struct dentry *dentry, const char *xattr_name);
> extern void evm_inode_post_removexattr(struct dentry *dentry,
> const char *xattr_name);
> -extern int evm_inode_init_security(struct inode *inode,
> - const struct xattr *xattr_array,
> - struct xattr *evm);
> +extern int evm_inode_init_security(struct inode *inode, struct inode *dir,
> + const struct qstr *qstr,
> + struct xattr *xattrs);
> extern bool evm_revalidate_status(const char *xattr_name);
> extern int evm_protected_xattr_if_enabled(const char *req_xattr_name);
> extern int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
> @@ -108,9 +108,9 @@ static inline void evm_inode_post_removexattr(struct dentry *dentry,
> return;
> }
>
> -static inline int evm_inode_init_security(struct inode *inode,
> - const struct xattr *xattr_array,
> - struct xattr *evm)
> +static inline int evm_inode_init_security(struct inode *inode, struct inode *dir,
> + const struct qstr *qstr,
> + struct xattr *xattrs)
> {
> return 0;
> }
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index 23d484e05e6f..0a312cafb7de 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -845,23 +845,29 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
> /*
> * evm_inode_init_security - initializes security.evm HMAC value
> */
> -int evm_inode_init_security(struct inode *inode,
> - const struct xattr *lsm_xattr,
> - struct xattr *evm_xattr)
> +int evm_inode_init_security(struct inode *inode, struct inode *dir,
> + const struct qstr *qstr,
> + struct xattr *xattrs)
> {
> struct evm_xattr *xattr_data;
> + struct xattr *xattr, *evm_xattr;
> int rc;
>
> - if (!(evm_initialized & EVM_INIT_HMAC) ||
> - !evm_protected_xattr(lsm_xattr->name))
> - return 0;
> + if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs ||
> + !evm_protected_xattr(xattrs->name))
> + return -EOPNOTSUPP;
> +
> + for (xattr = xattrs; xattr->value != NULL; xattr++)
> + ;
security_inode_init_security() already contains a comment for
allocating +2 extra space. Adding a similar comment here to explain
why walking the xattrs like this is safe would be nice.
> +
> + evm_xattr = xattr;
>
> xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
> if (!xattr_data)
> return -ENOMEM;
>
> xattr_data->data.type = EVM_XATTR_HMAC;
> - rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
> + rc = evm_init_hmac(inode, xattrs, xattr_data->digest);
> if (rc < 0)
> goto out;
>
> diff --git a/security/security.c b/security/security.c
> index 36804609caaa..44ce579daec1 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1190,9 +1190,8 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> if (!num_filled_xattrs)
> goto out;
>
> - ret = evm_inode_init_security(inode, new_xattrs,
> - new_xattrs + num_filled_xattrs);
> - if (ret)
> + ret = evm_inode_init_security(inode, dir, qstr, new_xattrs);
> + if (ret && ret != -EOPNOTSUPP)
> goto out;
> ret = initxattrs(inode, new_xattrs, fs_data);
> out:
next prev parent reply other threads:[~2023-02-19 19:42 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-01 10:41 [PATCH v7 0/6] evm: Do HMAC of multiple per LSM xattrs for new inodes Roberto Sassu
2022-12-01 10:41 ` [PATCH v7 1/6] reiserfs: Switch to security_inode_init_security() Roberto Sassu
2023-02-17 19:47 ` Mimi Zohar
2022-12-01 10:41 ` [PATCH v7 2/6] ocfs2: " Roberto Sassu
2023-01-10 8:55 ` Roberto Sassu
2023-01-12 17:21 ` Paul Moore
2023-02-08 14:33 ` Roberto Sassu
2023-02-09 21:05 ` Paul Moore
2023-02-21 6:45 ` Joseph Qi
2023-02-21 7:51 ` Roberto Sassu
2023-02-17 19:51 ` Mimi Zohar
2023-02-17 21:30 ` Mimi Zohar
2023-02-20 9:27 ` Roberto Sassu
2023-02-20 11:08 ` Mimi Zohar
2023-02-20 12:20 ` Roberto Sassu
2023-02-20 12:40 ` Mimi Zohar
2023-02-20 8:34 ` Roberto Sassu
2022-12-01 10:41 ` [PATCH v7 3/6] security: Remove security_old_inode_init_security() Roberto Sassu
2023-02-19 19:41 ` Mimi Zohar
2022-12-01 10:41 ` [PATCH v7 4/6] security: Allow all LSMs to provide xattrs for inode_init_security hook Roberto Sassu
2023-02-20 12:43 ` Mimi Zohar
2022-12-01 10:41 ` [PATCH v7 5/6] evm: Align evm_inode_init_security() definition with LSM infrastructure Roberto Sassu
2023-02-19 19:41 ` Mimi Zohar [this message]
2022-12-01 10:41 ` [PATCH v7 6/6] evm: Support multiple LSMs providing an xattr Roberto Sassu
2023-02-19 19:42 ` Mimi Zohar
2023-02-20 9:49 ` Roberto Sassu
2023-02-20 10:56 ` Mimi Zohar
2023-01-12 17:15 ` [PATCH v7 0/6] evm: Do HMAC of multiple per LSM xattrs for new inodes Paul Moore
2023-01-13 10:35 ` Roberto Sassu
2023-03-08 22:16 ` Paul Moore
2023-03-09 7:53 ` Roberto Sassu
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