security,fs,nfs,net: update security_inode_listsecurity() interface

Update the security_inode_listsecurity() interface to allow
use of the xattr_list_one() helper and update the hook
implementations.

Link: https://lore.kernel.org/selinux/20250424152822.2719-1-stephen.smalley.work@gmail.com
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[PM: forward porting to bring this patch up to v7.1-rc1+]
Signed-off-by: Paul Moore <paul@paul-moore.com>

fs/nfs/nfs4proc.c

@@ -10562,13 +10562,10 @@ static ssize_t nfs4_listxattr(struct dentry *dentry, char *list, size_t size)
 		left -= error;
 	}
 
-	error2 = security_inode_listsecurity(d_inode(dentry), list, left);
+	error2 = security_inode_listsecurity(d_inode(dentry), &list, &left);
 	if (error2 < 0)
 		return error2;
-	if (list) {
-		list += error2;
-		left -= error2;
-	}
+	error2 = size - error - left;
 
 	error3 = nfs4_listxattr_nfs4_user(d_inode(dentry), list, left);
 	if (error3 < 0)

fs/xattr.c

@@ -510,9 +510,12 @@ vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 	if (inode->i_op->listxattr) {
 		error = inode->i_op->listxattr(dentry, list, size);
 	} else {
-		error = security_inode_listsecurity(inode, list, size);
-		if (size && error > size)
-			error = -ERANGE;
+		ssize_t remaining = size;
+
+		error = security_inode_listsecurity(inode, &list, &remaining);
+		if (error)
+			return error;
+		error = size - remaining;
 	}
 	return error;
 }
@@ -1540,7 +1543,7 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
 	if (err)
 		return err;
 
-	err = security_inode_listsecurity(inode, buffer, remaining_size);
+	err = security_inode_listsecurity(inode, &buffer, &remaining_size);
 	if (err < 0)
 		return err;
 

include/linux/lsm_hook_defs.h

@@ -176,8 +176,8 @@ LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct mnt_idmap *idmap,
 	 struct inode *inode, const char *name, void **buffer, bool alloc)
 LSM_HOOK(int, -EOPNOTSUPP, inode_setsecurity, struct inode *inode,
 	 const char *name, const void *value, size_t size, int flags)
-LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
-	 size_t buffer_size)
+LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char **buffer,
+	 ssize_t *remaining_size)
 LSM_HOOK(void, LSM_RET_VOID, inode_getlsmprop, struct inode *inode,
 	 struct lsm_prop *prop)
 LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)

include/linux/security.h

@@ -459,7 +459,7 @@ int security_inode_getsecurity(struct mnt_idmap *idmap,
 			       struct inode *inode, const char *name,
 			       void **buffer, bool alloc);
 int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags);
-int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
+int security_inode_listsecurity(struct inode *inode, char **buffer, ssize_t *remaining_size);
 void security_inode_getlsmprop(struct inode *inode, struct lsm_prop *prop);
 int security_inode_copy_up(struct dentry *src, struct cred **new);
 int security_inode_copy_up_xattr(struct dentry *src, const char *name);
@@ -1097,7 +1097,8 @@ static inline int security_inode_setsecurity(struct inode *inode, const char *na
 	return -EOPNOTSUPP;
 }
 
-static inline int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size)
+static inline int security_inode_listsecurity(struct inode *inode,
+					char **buffer, ssize_t *remaining_size)
 {
 	return 0;
 }

security/security.c

@@ -2258,22 +2258,22 @@ int security_inode_setsecurity(struct inode *inode, const char *name,
 /**
  * security_inode_listsecurity() - List the xattr security label names
  * @inode: inode
- * @buffer: buffer
- * @buffer_size: size of buffer
+ * @buffer: pointer to buffer
+ * @remaining_size: pointer to remaining size of buffer
  *
  * Copy the extended attribute names for the security labels associated with
- * @inode into @buffer.  The maximum size of @buffer is specified by
- * @buffer_size.  @buffer may be NULL to request the size of the buffer
- * required.
+ * @inode into *(@buffer).  The remaining size of @buffer is specified by
+ * *(@remaining_size).  *(@buffer) may be NULL to request the size of the
+ * buffer required. Updates *(@buffer) and *(@remaining_size).
  *
- * Return: Returns number of bytes used/required on success.
+ * Return: Returns 0 on success, or -errno on failure.
  */
 int security_inode_listsecurity(struct inode *inode,
-				char *buffer, size_t buffer_size)
+				char **buffer, ssize_t *remaining_size)
 {
 	if (unlikely(IS_PRIVATE(inode)))
 		return 0;
-	return call_int_hook(inode_listsecurity, inode, buffer, buffer_size);
+	return call_int_hook(inode_listsecurity, inode, buffer, remaining_size);
 }
 EXPORT_SYMBOL(security_inode_listsecurity);
 

security/selinux/hooks.c

@@ -3684,16 +3684,12 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name,
 	return 0;
 }
 
-static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size)
+static int selinux_inode_listsecurity(struct inode *inode, char **buffer,
+				ssize_t *remaining_size)
 {
-	const int len = sizeof(XATTR_NAME_SELINUX);
-
 	if (!selinux_initialized())
 		return 0;
-
-	if (buffer && len <= buffer_size)
-		memcpy(buffer, XATTR_NAME_SELINUX, len);
-	return len;
+	return xattr_list_one(buffer, remaining_size, XATTR_NAME_SELINUX);
 }
 
 static void selinux_inode_getlsmprop(struct inode *inode, struct lsm_prop *prop)

security/smack/smack_lsm.c

@@ -1665,17 +1665,12 @@ static int smack_inode_getsecurity(struct mnt_idmap *idmap,
  * smack_inode_listsecurity - list the Smack attributes
  * @inode: the object
  * @buffer: where they go
- * @buffer_size: size of buffer
+ * @remaining_size: size of buffer
  */
-static int smack_inode_listsecurity(struct inode *inode, char *buffer,
-				    size_t buffer_size)
+static int smack_inode_listsecurity(struct inode *inode, char **buffer,
+				    ssize_t *remaining_size)
 {
-	int len = sizeof(XATTR_NAME_SMACK);
-
-	if (buffer != NULL && len <= buffer_size)
-		memcpy(buffer, XATTR_NAME_SMACK, len);
-
-	return len;
+	return xattr_list_one(buffer, remaining_size, XATTR_NAME_SMACK);
 }
 
 /**