[PATCH v10 15/25] security: Introduce inode_post_create_tmpfile hook

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu at huawei.com>

In preparation for moving IMA and EVM to the LSM infrastructure, introduce
the inode_post_create_tmpfile hook.

As temp files can be made persistent, treat new temp files like other new
files, so that the file hash is calculated and stored in the security
xattr.

LSMs could also take some action after temp files have been created.

The new hook cannot return an error and cannot cause the operation to be
canceled.

Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
Acked-by: Casey Schaufler <casey at schaufler-ca.com>
Reviewed-by: Mimi Zohar <zohar at linux.ibm.com>
Acked-by: Paul Moore <paul at paul-moore.com>
Acked-by: Christian Brauner <brauner at kernel.org>
Reviewed-by: Stefan Berger <stefanb at linux.ibm.com>
---
 fs/namei.c                    |  1 +
 include/linux/lsm_hook_defs.h |  2 ++
 include/linux/security.h      |  6 ++++++
 security/security.c           | 15 +++++++++++++++
 4 files changed, 24 insertions(+)

diff --git a/fs/namei.c b/fs/namei.c
index 9280aa5d60a7..c7ac7fdf0f25 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3705,6 +3705,7 @@ static int vfs_tmpfile(struct mnt_idmap *idmap,
 		inode->i_state |= I_LINKABLE;
 		spin_unlock(&inode->i_lock);
 	}
+	security_inode_post_create_tmpfile(idmap, inode);
 	ima_post_create_tmpfile(idmap, inode);
 	return 0;
 }
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index dba5d8204dc5..87f60b47dfca 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -121,6 +121,8 @@ LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
 	 const struct qstr *name, const struct inode *context_inode)
 LSM_HOOK(int, 0, inode_create, struct inode *dir, struct dentry *dentry,
 	 umode_t mode)
+LSM_HOOK(void, LSM_RET_VOID, inode_post_create_tmpfile, struct mnt_idmap *idmap,
+	 struct inode *inode)
 LSM_HOOK(int, 0, inode_link, struct dentry *old_dentry, struct inode *dir,
 	 struct dentry *new_dentry)
 LSM_HOOK(int, 0, inode_unlink, struct inode *dir, struct dentry *dentry)
diff --git a/include/linux/security.h b/include/linux/security.h
index 977dd9f7f51a..1cb604282617 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -344,6 +344,8 @@ int security_inode_init_security_anon(struct inode *inode,
 				      const struct qstr *name,
 				      const struct inode *context_inode);
 int security_inode_create(struct inode *dir, struct dentry *dentry, umode_t mode);
+void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
+					struct inode *inode);
 int security_inode_link(struct dentry *old_dentry, struct inode *dir,
 			 struct dentry *new_dentry);
 int security_inode_unlink(struct inode *dir, struct dentry *dentry);
@@ -811,6 +813,10 @@ static inline int security_inode_create(struct inode *dir,
 	return 0;
 }
 
+static inline void
+security_inode_post_create_tmpfile(struct mnt_idmap *idmap, struct inode *inode)
+{ }
+
 static inline int security_inode_link(struct dentry *old_dentry,
 				       struct inode *dir,
 				       struct dentry *new_dentry)
diff --git a/security/security.c b/security/security.c
index b55f9ad294cc..59d49e5c2671 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2014,6 +2014,21 @@ int security_inode_create(struct inode *dir, struct dentry *dentry,
 }
 EXPORT_SYMBOL_GPL(security_inode_create);
 
+/**
+ * security_inode_post_create_tmpfile() - Update inode security of new tmpfile
+ * @idmap: idmap of the mount
+ * @inode: inode of the new tmpfile
+ *
+ * Update inode security data after a tmpfile has been created.
+ */
+void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
+					struct inode *inode)
+{
+	if (unlikely(IS_PRIVATE(inode)))
+		return;
+	call_void_hook(inode_post_create_tmpfile, idmap, inode);
+}
+
 /**
  * security_inode_link() - Check if creating a hard link is allowed
  * @old_dentry: existing file
-- 
2.34.1