[PATCH v3 02/10] security: allow finer granularity in permitting copy-up of security xattrs

[Stefan Berger]

Copying up xattrs is solely based on the security xattr name. For finer
granularity add a dentry parameter to the security_inode_copy_up_xattr
hook definition, allowing decisions to be based on the xattr content as
well.

Co-developed-by: Mimi Zohar <zohar at linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
Acked-by: Amir Goldstein <amir73il at gmail.com>
---
 fs/overlayfs/copy_up.c            | 2 +-
 include/linux/lsm_hook_defs.h     | 3 ++-
 include/linux/security.h          | 4 ++--
 security/integrity/evm/evm_main.c | 2 +-
 security/security.c               | 5 +++--
 security/selinux/hooks.c          | 2 +-
 security/smack/smack_lsm.c        | 2 +-
 7 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index b8e25ca51016..bd9ddcefb7a7 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -114,7 +114,7 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
 		if (ovl_is_private_xattr(sb, name))
 			continue;
 
-		error = security_inode_copy_up_xattr(name);
+		error = security_inode_copy_up_xattr(old, name);
 		if (error < 0 && error != -EOPNOTSUPP)
 			break;
 		if (error == 1) {
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 7e4683035d34..c538d39dd9a9 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -176,7 +176,8 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
 	 size_t buffer_size)
 LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)
 LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
-LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name)
+LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, struct dentry *src,
+	 const char *name)
 LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,
 	 struct kernfs_node *kn)
 LSM_HOOK(int, 0, file_permission, struct file *file, int mask)
diff --git a/include/linux/security.h b/include/linux/security.h
index 8436f9abf43d..2553a4f4b726 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -397,7 +397,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void
 int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
 void security_inode_getsecid(struct inode *inode, u32 *secid);
 int security_inode_copy_up(struct dentry *src, struct cred **new);
-int security_inode_copy_up_xattr(const char *name);
+int security_inode_copy_up_xattr(struct dentry *src, const char *name);
 int security_kernfs_init_security(struct kernfs_node *kn_dir,
 				  struct kernfs_node *kn);
 int security_file_permission(struct file *file, int mask);
@@ -1015,7 +1015,7 @@ static inline int security_kernfs_init_security(struct kernfs_node *kn_dir,
 	return 0;
 }
 
-static inline int security_inode_copy_up_xattr(const char *name)
+static inline int security_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 81dbade5b9b3..b0a862bfd74a 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -946,7 +946,7 @@ static void evm_inode_post_setattr(struct mnt_idmap *idmap,
 		evm_update_evmxattr(dentry, NULL, NULL, 0);
 }
 
-static int evm_inode_copy_up_xattr(const char *name)
+static int evm_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	if (strcmp(name, XATTR_NAME_EVM) == 0)
 		return 1; /* Discard */
diff --git a/security/security.c b/security/security.c
index b95772333d05..8d8b89e6b5d9 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2622,6 +2622,7 @@ EXPORT_SYMBOL(security_inode_copy_up);
 
 /**
  * security_inode_copy_up_xattr() - Filter xattrs in an overlayfs copy-up op
+ * @src: union dentry of copy-up file
  * @name: xattr name
  *
  * Filter the xattrs being copied up when a unioned file is copied up from a
@@ -2632,7 +2633,7 @@ EXPORT_SYMBOL(security_inode_copy_up);
  *         if the security module does not know about attribute, or a negative
  *         error code to abort the copy up.
  */
-int security_inode_copy_up_xattr(const char *name)
+int security_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	int rc;
 
@@ -2641,7 +2642,7 @@ int security_inode_copy_up_xattr(const char *name)
 	 * xattr), -EOPNOTSUPP if it does not know anything about the xattr or
 	 * any other error code in case of an error.
 	 */
-	rc = call_int_hook(inode_copy_up_xattr, name);
+	rc = call_int_hook(inode_copy_up_xattr, src, name);
 	if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr))
 		return rc;
 
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index cedb4cbf072e..1d2395d8bba7 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3531,7 +3531,7 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
 	return 0;
 }
 
-static int selinux_inode_copy_up_xattr(const char *name)
+static int selinux_inode_copy_up_xattr(struct dentry *dentry, const char *name)
 {
 	/* The copy_up hook above sets the initial context on an inode, but we
 	 * don't then want to overwrite it by blindly copying all the lower
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 1b6abfdf7173..972d50e3f266 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4875,7 +4875,7 @@ static int smack_inode_copy_up(struct dentry *dentry, struct cred **new)
 	return 0;
 }
 
-static int smack_inode_copy_up_xattr(const char *name)
+static int smack_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	/*
 	 * Return 1 if this is the smack access Smack attribute.
-- 
2.43.0