linux-hardening - [PATCH 07/19] hypfs: use d

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Date:   Wed, 13 Sep 2023 08:10:01 -0300
From:   Christoph Hellwig <hch@....de>
To:     Christian Brauner <brauner@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>
Cc:     Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Tejun Heo <tj@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Damien Le Moal <dlemoal@...nel.org>,
        Naohiro Aota <naohiro.aota@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-hardening@...r.kernel.org,
        cgroups@...r.kernel.org
Subject: [PATCH 07/19] hypfs: use d_genocide to kill fs entries

hypfs is entirely synthetic and doesn't care about i_nlink when dropping
entries from the cache.  Switch to d_genocide instead of a home grown
file remove loop for unmount and write (yes, really!).

Signed-off-by: Christoph Hellwig <hch@....de>
---
 arch/s390/hypfs/inode.c | 37 ++-----------------------------------
 1 file changed, 2 insertions(+), 35 deletions(-)

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index dbe8a7dcafa922..3261fb9cade648 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -64,33 +64,6 @@ static void hypfs_add_dentry(struct dentry *dentry)
 	hypfs_last_dentry = dentry;
 }
 
-static void hypfs_remove(struct dentry *dentry)
-{
-	struct dentry *parent;
-
-	parent = dentry->d_parent;
-	inode_lock(d_inode(parent));
-	if (simple_positive(dentry)) {
-		if (d_is_dir(dentry))
-			simple_rmdir(d_inode(parent), dentry);
-		else
-			simple_unlink(d_inode(parent), dentry);
-	}
-	d_drop(dentry);
-	dput(dentry);
-	inode_unlock(d_inode(parent));
-}
-
-static void hypfs_delete_tree(struct dentry *root)
-{
-	while (hypfs_last_dentry) {
-		struct dentry *next_dentry;
-		next_dentry = hypfs_last_dentry->d_fsdata;
-		hypfs_remove(hypfs_last_dentry);
-		hypfs_last_dentry = next_dentry;
-	}
-}
-
 static struct inode *hypfs_make_inode(struct super_block *sb, umode_t mode)
 {
 	struct inode *ret = new_inode(sb);
@@ -183,14 +156,14 @@ static ssize_t hypfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		rc = -EBUSY;
 		goto out;
 	}
-	hypfs_delete_tree(sb->s_root);
+	d_genocide(sb->s_root);
 	if (MACHINE_IS_VM)
 		rc = hypfs_vm_create_files(sb->s_root);
 	else
 		rc = hypfs_diag_create_files(sb->s_root);
 	if (rc) {
 		pr_err("Updating the hypfs tree failed\n");
-		hypfs_delete_tree(sb->s_root);
+		d_genocide(sb->s_root);
 		goto out;
 	}
 	hypfs_update_update(sb);
@@ -323,12 +296,6 @@ static int hypfs_init_fs_context(struct fs_context *fc)
 
 static void hypfs_kill_super(struct super_block *sb)
 {
-	struct hypfs_sb_info *sb_info = sb->s_fs_info;
-
-	if (sb->s_root)
-		hypfs_delete_tree(sb->s_root);
-	if (sb_info && sb_info->update_file)
-		hypfs_remove(sb_info->update_file);
 	kill_litter_super(sb);
 	kfree(sb->s_fs_info);
 }
-- 
2.39.2