[PATCH v12 3/4] evm: Align evm_inode_init_security() definition with LSM infrastructure

Roberto Sassu
2023-06-10T07:59:26Z

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 the
xattr array allocated by security_inode_init_security(), and the number of
xattrs filled by previously invoked LSMs.

Use the newly introduced lsm_get_xattr_slot() to position EVM correctly in
the xattrs array, like a regular LSM, and to increment the number of filled
slots. For now, the LSM infrastructure allocates enough xattrs slots to
store the EVM xattr, without using the reservation mechanism.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
include/linux/evm.h | 14 ++++++++------
security/integrity/evm/evm_main.c | 16 ++++++++++------
security/security.c | 4 ++--
3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/include/linux/evm.h b/include/linux/evm.h
index 7dc1ee74169..01fc495a83e 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -56,9 +56,10 @@ static inline void evm_inode_post_set_acl(struct dentry *dentry,
{
return evm_inode_post_setxattr(dentry, acl_name, NULL, 0);
}
-extern int evm_inode_init_security(struct inode *inode,
- const struct xattr *xattr_array,
- struct xattr *evm);
+
+int evm_inode_init_security(struct inode *inode, struct inode *dir,
+ const struct qstr *qstr, struct xattr *xattrs,
+ int *xattr_count);
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,
@@ -157,9 +158,10 @@ static inline void evm_inode_post_set_acl(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,
+ int *xattr_count)
{
return 0;
}
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index cf24c525558..475196ce712 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -21,6 +21,7 @@
#include <linux/evm.h>
#include <linux/magic.h>
#include <linux/posix_acl_xattr.h>
+#include <linux/lsm_hooks.h>

#include <crypto/hash.h>
#include <crypto/hash_info.h>
@@ -864,23 +865,26 @@ 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,
+ int *xattr_count)
{
struct evm_xattr *xattr_data;
+ struct xattr *evm_xattr;
int rc;

- if (!(evm_initialized & EVM_INIT_HMAC) ||
- !evm_protected_xattr(lsm_xattr->name))
+ if (!(evm_initialized & EVM_INIT_HMAC) || !xattrs ||
+ !evm_protected_xattr(xattrs->name))
return 0;

+ evm_xattr = lsm_get_xattr_slot(xattrs, xattr_count);
+
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 d5ef7df1ce4..819294d91ad 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1645,8 +1645,8 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
if (!xattr_count)
goto out;

- ret = evm_inode_init_security(inode, new_xattrs,
- &new_xattrs[xattr_count]);
+ ret = evm_inode_init_security(inode, dir, qstr, new_xattrs,
+ &xattr_count);
if (ret)
goto out;
ret = initxattrs(inode, new_xattrs, fs_data);
--
2.25.1