[SRU][J][PATCH 1/1] fs/ntfs3: cancle set bad inode after removing name fails

[Cengiz Can]

From: Edward Adam Davis <eadavis at qq.com>

The reproducer uses a file0 on a ntfs3 file system with a corrupted i_link.
When renaming, the file0's inode is marked as a bad inode because the file
name cannot be deleted.

The underlying bug is that make_bad_inode() is called on a live inode.
In some cases it's "icache lookup finds a normal inode, d_splice_alias()
is called to attach it to dentry, while another thread decides to call
make_bad_inode() on it - that would evict it from icache, but we'd already
found it there earlier".
In some it's outright "we have an inode attached to dentry - that's how we
got it in the first place; let's call make_bad_inode() on it just for shits
and giggles".

Fixes: 78ab59fee07f ("fs/ntfs3: Rework file operations")
Reported-by: syzbot+1aa90f0eb1fc3e77d969 at syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1aa90f0eb1fc3e77d969
Signed-off-by: Edward Adam Davis <eadavis at qq.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich at paragon-software.com>
(backported from commit d99208b91933fd2a58ed9ed321af07dacd06ddc3)
[bot_kybele: Dropped the is_bad path in ntfs_rename but kept this tree's older
 inode->i_ctime/i_mtime = current_time(dir) block since
 simple_rename_timestamp() does not exist here; also removed the tree's extra
 make_bad_inode/ntfs_inode_err/ntfs_set_state error handling that upstream had
 already reduced to _ntfs_bad_inode.]
CVE-2025-38615
Assisted-by: kybele:claude-opus-4.8
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 fs/ntfs3/frecord.c |  7 +++----
 fs/ntfs3/namei.c   | 12 +++---------
 fs/ntfs3/ntfs_fs.h |  3 +--
 3 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index 62874e7f8d8f..2b082ec2d269 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -3026,8 +3026,7 @@ int ni_add_name(struct ntfs_inode *dir_ni, struct ntfs_inode *ni,
  * ni_rename - Remove one name and insert new name.
  */
 int ni_rename(struct ntfs_inode *dir_ni, struct ntfs_inode *new_dir_ni,
-	      struct ntfs_inode *ni, struct NTFS_DE *de, struct NTFS_DE *new_de,
-	      bool *is_bad)
+	      struct ntfs_inode *ni, struct NTFS_DE *de, struct NTFS_DE *new_de)
 {
 	int err;
 	struct NTFS_DE *de2 = NULL;
@@ -3050,8 +3049,8 @@ int ni_rename(struct ntfs_inode *dir_ni, struct ntfs_inode *new_dir_ni,
 	err = ni_add_name(new_dir_ni, ni, new_de);
 	if (!err) {
 		err = ni_remove_name(dir_ni, ni, de, &de2, &undo);
-		if (err && ni_remove_name(new_dir_ni, ni, new_de, &de2, &undo))
-			*is_bad = true;
+		WARN_ON(err && ni_remove_name(new_dir_ni, ni, new_de, &de2,
+			&undo));
 	}
 
 	/*
diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
index 9d454b9a9c14..1adbc4af6aba 100644
--- a/fs/ntfs3/namei.c
+++ b/fs/ntfs3/namei.c
@@ -250,7 +250,7 @@ static int ntfs_rename(struct user_namespace *mnt_userns, struct inode *dir,
 	struct ntfs_inode *ni = ntfs_i(inode);
 	struct inode *new_inode = d_inode(new_dentry);
 	struct NTFS_DE *de, *new_de;
-	bool is_same, is_bad;
+	bool is_same;
 	/*
 	 * de		- memory of PATH_MAX bytes:
 	 * [0-1024)	- original name (dentry->d_name)
@@ -314,14 +314,8 @@ static int ntfs_rename(struct user_namespace *mnt_userns, struct inode *dir,
 	ni_lock_dir(dir_ni);
 	ni_lock(ni);
 
-	is_bad = false;
-	err = ni_rename(dir_ni, new_dir_ni, ni, de, new_de, &is_bad);
-	if (is_bad) {
-		/* Restore after failed rename failed too. */
-		make_bad_inode(inode);
-		ntfs_inode_err(inode, "failed to undo rename");
-		ntfs_set_state(sbi, NTFS_DIRTY_ERROR);
-	} else if (!err) {
+	err = ni_rename(dir_ni, new_dir_ni, ni, de, new_de);
+	if (!err) {
 		inode->i_ctime = dir->i_ctime = dir->i_mtime =
 			current_time(dir);
 		mark_inode_dirty(inode);
diff --git a/fs/ntfs3/ntfs_fs.h b/fs/ntfs3/ntfs_fs.h
index d93cba03a65a..4718830ebef7 100644
--- a/fs/ntfs3/ntfs_fs.h
+++ b/fs/ntfs3/ntfs_fs.h
@@ -573,8 +573,7 @@ int ni_add_name(struct ntfs_inode *dir_ni, struct ntfs_inode *ni,
 		struct NTFS_DE *de);
 
 int ni_rename(struct ntfs_inode *dir_ni, struct ntfs_inode *new_dir_ni,
-	      struct ntfs_inode *ni, struct NTFS_DE *de, struct NTFS_DE *new_de,
-	      bool *is_bad);
+	      struct ntfs_inode *ni, struct NTFS_DE *de, struct NTFS_DE *new_de);
 
 bool ni_is_dirty(struct inode *inode);
 
-- 
2.53.0