[v1,2/2] lsm: Refactor return value of LSM hook inode_copy_up_xattr

Commit Message

Xu Kuohai July 24, 2024, 2:06 a.m. UTC

From: Xu Kuohai <[e-mail]>

To be consistent with most LSM hooks, convert the return value of
hook inode_copy_up_xattr to 0 or a negative error code.

Before:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, 1 when
  discarding xattr, -EOPNOTSUPP if it does not know xattr, or any
  other negative error code otherwise.

After:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, *-ECANCELED*
  when discarding xattr, -EOPNOTSUPP if it does not know xattr, or
  any other negative error code otherwise.

Signed-off-by: Xu Kuohai <[e-mail]>
---
 fs/overlayfs/copy_up.c            |  6 +++---
 security/integrity/evm/evm_main.c |  2 +-
 security/security.c               | 11 +++--------
 security/selinux/hooks.c          |  4 ++--
 security/smack/smack_lsm.c        |  6 +++---
 5 files changed, 12 insertions(+), 17 deletions(-)

Patch

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index a5ef2005a2cc..337a5be99ac9 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -115,12 +115,12 @@  int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
 			continue;
 
 		error = security_inode_copy_up_xattr(old, name);
-		if (error < 0 && error != -EOPNOTSUPP)
-			break;
-		if (error == 1) {
+		if (error == -ECANCELED) {
 			error = 0;
 			continue; /* Discard */
 		}
+		if (error < 0 && error != -EOPNOTSUPP)
+			break;
 
 		if (is_posix_acl_xattr(name)) {
 			error = ovl_copy_acl(OVL_FS(sb), oldpath, new, name);
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 62fe66dd53ce..6924ed508ebd 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -1000,7 +1000,7 @@  static int evm_inode_copy_up_xattr(struct dentry *src, const char *name)
 	case EVM_XATTR_HMAC:
 	case EVM_IMA_XATTR_DIGSIG:
 	default:
-		rc = 1; /* discard */
+		rc = -ECANCELED; /* discard */
 	}
 
 	kfree(xattr_data);
diff --git a/security/security.c b/security/security.c
index ff5cca992ee1..ca93d43ad475 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2760,19 +2760,14 @@  EXPORT_SYMBOL(security_inode_copy_up);
  * lower layer to the union/overlay layer.   The caller is responsible for
  * reading and writing the xattrs, this hook is merely a filter.
  *
- * Return: Returns 0 to accept the xattr, 1 to discard the xattr, -EOPNOTSUPP
- *         if the security module does not know about attribute, or a negative
- *         error code to abort the copy up.
+ * Return: Returns 0 to accept the xattr, -ECANCELED to discard the xattr,
+ *         -EOPNOTSUPP 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(struct dentry *src, const char *name)
 {
 	int rc;
 
-	/*
-	 * The implementation can return 0 (accept the xattr), 1 (discard the
-	 * 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, 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 af7467cdd181..81fbfa5b80d4 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3531,8 +3531,8 @@  static int selinux_inode_copy_up_xattr(struct dentry *dentry, const char *name)
 	 * xattrs up.  Instead, filter out SELinux-related xattrs following
 	 * policy load.
 	 */
-	if (selinux_initialized() && strcmp(name, XATTR_NAME_SELINUX) == 0)
-		return 1; /* Discard */
+	if (selinux_initialized() && !strcmp(name, XATTR_NAME_SELINUX))
+		return -ECANCELED; /* Discard */
 	/*
 	 * Any other attribute apart from SELINUX is not claimed, supported
 	 * by selinux.
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index b0e0205a5724..09ff7f24c0c6 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4902,10 +4902,10 @@  static int smack_inode_copy_up(struct dentry *dentry, struct cred **new)
 static int smack_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	/*
-	 * Return 1 if this is the smack access Smack attribute.
+	 * Return -ECANCELED if this is the smack access Smack attribute.
 	 */
-	if (strcmp(name, XATTR_NAME_SMACK) == 0)
-		return 1;
+	if (!strcmp(name, XATTR_NAME_SMACK))
+		return -ECANCELED;
 
 	return -EOPNOTSUPP;
 }