linux-kernel - [RFC PATCH v3 46/59] do_{renameat2,linkat,symlinkat}(): use CLASS(filename

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Message-ID: <20251216035518.4037331-47-viro@zeniv.linux.org.uk>
Date: Tue, 16 Dec 2025 03:55:05 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: linux-fsdevel@...r.kernel.org
Cc: torvalds@...ux-foundation.org,
	brauner@...nel.org,
	jack@...e.cz,
	mjguzik@...il.com,
	paul@...l-moore.com,
	axboe@...nel.dk,
	audit@...r.kernel.org,
	io-uring@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH v3 46/59] do_{renameat2,linkat,symlinkat}(): use CLASS(filename_consume)

more explicit in what we do, lower odds of ending up with a leak,
fewer gotos...

... and if at some point in the future we decide to make some of those
non-consuming, it would be less noisy.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 51 +++++++++++++++++++++------------------------------
 1 file changed, 21 insertions(+), 30 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index f6b5d6a657da..fbf306fe8414 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5575,23 +5575,22 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 }
 EXPORT_SYMBOL(vfs_symlink);
 
-int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
+int do_symlinkat(struct filename *__from, int newdfd, struct filename *__to)
 {
+	CLASS(filename_consume, from)(__from);
+	CLASS(filename_consume, to)(__to);
 	int error;
 	struct dentry *dentry;
 	struct path path;
 	unsigned int lookup_flags = 0;
 	struct delegated_inode delegated_inode = { };
 
-	if (IS_ERR(from)) {
-		error = PTR_ERR(from);
-		goto out_putnames;
-	}
+	if (IS_ERR(from))
+		return PTR_ERR(from);
 retry:
 	dentry = filename_create(newdfd, to, &path, lookup_flags);
-	error = PTR_ERR(dentry);
 	if (IS_ERR(dentry))
-		goto out_putnames;
+		return PTR_ERR(dentry);
 
 	error = security_path_symlink(&path, dentry, from->name);
 	if (!error)
@@ -5607,9 +5606,6 @@ int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
-out_putnames:
-	putname(to);
-	putname(from);
 	return error;
 }
 
@@ -5724,9 +5720,11 @@ EXPORT_SYMBOL(vfs_link);
  * with linux 2.0, and to avoid hard-linking to directories
  * and other special files.  --ADM
  */
-int do_linkat(int olddfd, struct filename *old, int newdfd,
-	      struct filename *new, int flags)
+int do_linkat(int olddfd, struct filename *__old, int newdfd,
+	      struct filename *__new, int flags)
 {
+	CLASS(filename_consume, old)(__old);
+	CLASS(filename_consume, new)(__new);
 	struct mnt_idmap *idmap;
 	struct dentry *new_dentry;
 	struct path old_path, new_path;
@@ -5734,10 +5732,8 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 	int how = 0;
 	int error;
 
-	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
-		error = -EINVAL;
-		goto out_putnames;
-	}
+	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
+		return -EINVAL;
 	/*
 	 * To use null names we require CAP_DAC_READ_SEARCH or
 	 * that the open-time creds of the dfd matches current.
@@ -5752,7 +5748,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 retry:
 	error = filename_lookup(olddfd, old, how, &old_path, NULL);
 	if (error)
-		goto out_putnames;
+		return error;
 
 	new_dentry = filename_create(newdfd, new, &new_path,
 					(how & LOOKUP_REVAL));
@@ -5788,10 +5784,6 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 	}
 out_putpath:
 	path_put(&old_path);
-out_putnames:
-	putname(old);
-	putname(new);
-
 	return error;
 }
 
@@ -6022,9 +6014,11 @@ int vfs_rename(struct renamedata *rd)
 }
 EXPORT_SYMBOL(vfs_rename);
 
-int do_renameat2(int olddfd, struct filename *from, int newdfd,
-		 struct filename *to, unsigned int flags)
+int do_renameat2(int olddfd, struct filename *__from, int newdfd,
+		 struct filename *__to, unsigned int flags)
 {
+	CLASS(filename_consume, from)(__from);
+	CLASS(filename_consume, to)(__to);
 	struct renamedata rd;
 	struct path old_path, new_path;
 	struct qstr old_last, new_last;
@@ -6032,20 +6026,20 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
 	struct delegated_inode delegated_inode = { };
 	unsigned int lookup_flags = 0;
 	bool should_retry = false;
-	int error = -EINVAL;
+	int error;
 
 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
-		goto put_names;
+		return -EINVAL;
 
 	if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
 	    (flags & RENAME_EXCHANGE))
-		goto put_names;
+		return -EINVAL;
 
 retry:
 	error = filename_parentat(olddfd, from, lookup_flags, &old_path,
 				  &old_last, &old_type);
 	if (error)
-		goto put_names;
+		return error;
 
 	error = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last,
 				  &new_type);
@@ -6122,9 +6116,6 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
-put_names:
-	putname(from);
-	putname(to);
 	return error;
 }
 
-- 
2.47.3