[PATCH v4 1/3] lsm: introduce new hooks for setting/getting inode fsxattr

[Andrey Albershteyn <aalbersh@redhat.com>]

Introduce new hooks for setting and getting filesystem extended
attributes on inode (FS_IOC_FSGETXATTR).

Cc: selinux@vger.kernel.org
Cc: Paul Moore <paul@paul-moore.com>

Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
---
 fs/ioctl.c                    |  7 ++++++-
 include/linux/lsm_hook_defs.h |  4 ++++
 include/linux/security.h      | 16 ++++++++++++++++
 security/security.c           | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 638a36be31c14afc66a7fd6eb237d9545e8ad997..4434c97bc5dff5a3e8635e28745cd99404ff353e 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -525,10 +525,15 @@ EXPORT_SYMBOL(fileattr_fill_flags);
 int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 {
 	struct inode *inode = d_inode(dentry);
+	int error;
 
 	if (!inode->i_op->fileattr_get)
 		return -ENOIOCTLCMD;
 
+	error = security_inode_getfsxattr(inode, fa);
+	if (error)
+		return error;
+
 	return inode->i_op->fileattr_get(dentry, fa);
 }
 EXPORT_SYMBOL(vfs_fileattr_get);
@@ -692,7 +697,7 @@ int vfs_fileattr_set(struct mnt_idmap *idmap, struct dentry *dentry,
 			fa->flags |= old_ma.flags & ~FS_COMMON_FL;
 		}
 		err = fileattr_set_prepare(inode, &old_ma, fa);
-		if (!err)
+		if (!err && !security_inode_setfsxattr(inode, fa))
 			err = inode->i_op->fileattr_set(idmap, dentry, fa);
 	}
 	inode_unlock(inode);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index eb2937599cb029004f491012b3bf5a3d6d2731df..49e64d23e9049568af133bf3f30ca719c9ec5f25 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -157,6 +157,10 @@ LSM_HOOK(int, 0, inode_removexattr, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *name)
 LSM_HOOK(void, LSM_RET_VOID, inode_post_removexattr, struct dentry *dentry,
 	 const char *name)
+LSM_HOOK(int, 0, inode_setfsxattr, const struct inode *inode,
+	 const struct fileattr *fa)
+LSM_HOOK(int, 0, inode_getfsxattr, const struct inode *inode,
+	 const struct fileattr *fa)
 LSM_HOOK(int, 0, inode_set_acl, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *acl_name, struct posix_acl *kacl)
 LSM_HOOK(void, LSM_RET_VOID, inode_post_set_acl, struct dentry *dentry,
diff --git a/include/linux/security.h b/include/linux/security.h
index cbdba435b798660130779d6919388779edd41d54..dd58ace29c6e325ee49470596d0abb6ecc38ba07 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -439,6 +439,10 @@ int security_inode_listxattr(struct dentry *dentry);
 int security_inode_removexattr(struct mnt_idmap *idmap,
 			       struct dentry *dentry, const char *name);
 void security_inode_post_removexattr(struct dentry *dentry, const char *name);
+int security_inode_setfsxattr(const struct inode *inode,
+			      const struct fileattr *fa);
+int security_inode_getfsxattr(const struct inode *inode,
+			      const struct fileattr *fa);
 int security_inode_need_killpriv(struct dentry *dentry);
 int security_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry);
 int security_inode_getsecurity(struct mnt_idmap *idmap,
@@ -1042,6 +1046,18 @@ static inline void security_inode_post_removexattr(struct dentry *dentry,
 						   const char *name)
 { }
 
+static inline int security_inode_setfsxattr(const struct inode *inode,
+					    const struct fileattr *fa)
+{
+	return 0;
+}
+
+static inline int security_inode_getfsxattr(const struct inode *inode,
+					    const struct fileattr *fa)
+{
+	return 0;
+}
+
 static inline int security_inode_need_killpriv(struct dentry *dentry)
 {
 	return cap_inode_need_killpriv(dentry);
diff --git a/security/security.c b/security/security.c
index 09664e09fec9a1d502a23847aa2e87a6d19837db..d3b527f55ed52209d8e22c05adf278b164374d35 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2617,6 +2617,38 @@ void security_inode_post_removexattr(struct dentry *dentry, const char *name)
 	call_void_hook(inode_post_removexattr, dentry, name);
 }
 
+/**
+ * security_inode_setfsxattr() - check if setting fsxattr is allowed
+ * @inode: inode to set filesystem extended attributes on
+ * @fa: extended attributes to set on the inode
+ *
+ * Called when setfsxattrat() syscall or FS_IOC_FSSETXATTR ioctl() is called on
+ * inode
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_inode_setfsxattr(const struct inode *inode,
+			      const struct fileattr *fa)
+{
+	return call_int_hook(inode_setfsxattr, inode, fa);
+}
+
+/**
+ * security_inode_getfsxattr() - check if retrieving fsxattr is allowed
+ * @inode: inode to retrieve filesystem extended attributes from
+ * @fa: extended attributes to get
+ *
+ * Called when getfsxattrat() syscall or FS_IOC_FSGETXATTR ioctl() is called on
+ * inode
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_inode_getfsxattr(const struct inode *inode,
+			      const struct fileattr *fa)
+{
+	return call_int_hook(inode_getfsxattr, inode, fa);
+}
+
 /**
  * security_inode_need_killpriv() - Check if security_inode_killpriv() required
  * @dentry: associated dentry

-- 
2.47.2