FAILED: patch "[PATCH] fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and" failed to apply to 6.1-stable tree

PATCH New [email protected] 2 participants 3 messages Sep 29

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author maintainer

2026-09-29 06:44 UTC #0 lore raw

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 1abd643f3783ea8f8e273c18697ff0413aa92dc7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026092905-banter-curable-1b52@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1abd643f3783ea8f8e273c18697ff0413aa92dc7 Mon Sep 17 00:00:00 2001
From: Christian Brauner <[email protected]>
Date: Wed, 9 Sep 2026 11:03:18 +0200
Subject: [PATCH] fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and
murder syzbot's "WARNING in do_new_mount" saga

ntfs_create_inode() creates a new inode via ntfs_new_inode(). It hashes it with insert_inode_locked() and so it's marked as I_NEW until unlock_new_inode().

ntfs 3 calls d_instantiate() in between though... Since the dentry was already hashed by the lookup before the create any path walk finds it without touching the parent's i_rwsem and so can lock the inode.

If the inode is a directory unlock_new_inode() calls lockdep_annotate_inode_mutex_key() and marks i_rwsem with the i_mutex_dir_key class.

That resets the count and the owner of a lock somebody else may already hold by now...

syzbot has been spamming us with the same godforsaken bug

"WARNING in do_new_mount"

since 2023. I can't take it anymore so I went looking. Afaict, syzbot's executor chdirs into a freshly mounted ntfs3 image, creates a directory and then mounts some pseudofs on it. Everytime the mkdir() takes longer than syzbot waits mount() runs concurrently:

mkdir("./sys") mount(NULL, "./sys", "sysfs")
ntfs_create_inode()

    d_instantiate()
                                        user_path_at() finds the dentry
                                        do_lock_mount()
                                          inode_lock(inode)
                                          namespace_lock()
    unlock_new_inode()
      lockdep_annotate_inode_mutex_key()
        init_rwsem(&inode->i_rwsem)
                                        unlock_mount()
                                          inode_unlock(inode)

The mount side then releases a lock that according to the rwsem nobody holds:

DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && ...):
count = 0x0, magic = 0xffff888043a854e8, owner = 0x0, curr 0xffff888000244880, list empty

  WARNING: CPU: 0 PID: 5346 at kernel/locking/rwsem.c:1368 __up_write
  Call Trace:
   inode_unlock include/linux/fs.h:877 [inline]
   unlock_mount fs/namespace.c:2892 [inline]
   do_new_mount_fc fs/namespace.c:3828 [inline]
   do_new_mount+0x777/0xa40 fs/namespace.c:3887

On PREEMPT_RT the same thing shows up as

DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)

  WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock

The up_write() underflows the reset count. A following inode_lock() on that directory then never returns. A path walk into the new directory racing with the mkdir() corrupts the lock the same way via inode_lock_shared() in lookup_slow().

Switch to d_instantiate_new() and drop the trailing unlock_new_inode(). All error paths bail out before that point with I_NEW still set and keep using discard_new_inode().

May we never see this fscking bug report again.

Link https://patch.msgid.link/20260909-work-ntfs3-d_instantiate_new-v1-1-2db697162ce8@kernel.org open here

Fixes 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")

Reviewed-by Jan Kara <[email protected]>

Cc [email protected] # v5.15+

Reported-by [email protected]

Closes https://lore.kernel.org/[email protected] open here

Signed-off-by Christian Brauner (Amutable) <[email protected]>

fs/ntfs3/inode.c +2 -5

index 56b4f6469a28..4ac26c80bd34 100644
@@ -1866,10 +1866,10 @@ int ntfs_create_inode(struct mnt_idmap *idmap, struct inode *dir,
 		goto out6;
 
 	/*
-	 * Call 'd_instantiate' after inode->i_op is set
+	 * Call 'd_instantiate_new' after inode->i_op is set
 	 * but before finish_open.
 	 */
-	d_instantiate(dentry, inode);
+	d_instantiate_new(dentry, inode);
 
 	/* Set original time. inode times (i_ctime) may be changed in ntfs_init_acl. */
 	inode_set_atime_to_ts(inode, ni->i_crtime);

@@ -1917,9 +1917,6 @@ int ntfs_create_inode(struct mnt_idmap *idmap, struct inode *dir,
 	if (!fnd)
 		ni_unlock(dir_ni);
 
-	if (!err)
-		unlock_new_inode(inode);
-
 	return err;
 }

Sasha Levin

maintainer

2026-09-29 14:12 UTC #1 lore raw

PATCH 1/2 fs/ntfs3: Redesign ntfs_create_inode to return error code instead of inode

From: Konstantin Komarov <[email protected]>

[ Upstream commit c935c66878867dc87c36c36b21d35d7e7f08adec ]

As Al Viro correctly pointed out, there is no need to return the whole structure to check the error.
https://lore.kernel.org/ntfs3/20240322023515.GK538574@ZenIV/

Acked-by Al Viro <[email protected]>

Signed-off-by Konstantin Komarov <[email protected]>

[Stable 6.1 dependency adaptation: retain the user_namespace API and existing directory-lock lifetime. Return an integer status from ntfs_create_inode and pass it through all four callers. Omit the unrelated switch to resident data for newly created regular files. The success-only unlock_new_inode epilogue allows target 1abd643f3783ea8f8e273c18697ff0413aa92dc7 to apply cleanly.]

Stable-dep-of: 1abd643f3783 ("fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's "WARNING in do_new_mount" saga")

Signed-off-by Sasha Levin <[email protected]>

---
 fs/ntfs3/inode.c   | 18 ++++++++----------
 fs/ntfs3/namei.c   | 31 ++++++++-----------------------
 fs/ntfs3/ntfs_fs.h |  9 ++++-----
 3 files changed, 20 insertions(+), 38 deletions(-)

fs/ntfs3/inode.c +8 ~~-10~~

index b8ac0943e9325..98f70c721052b 100644
@@ -1198,11 +1198,10 @@ ntfs_create_reparse_buffer(struct ntfs_sb_info *sbi, const char *symname,
 	return ERR_PTR(err);
 }
 
-struct inode *ntfs_create_inode(struct user_namespace *mnt_userns,
-				struct inode *dir, struct dentry *dentry,
-				const struct cpu_str *uni, umode_t mode,
-				dev_t dev, const char *symname, u32 size,
-				struct ntfs_fnd *fnd)
+int ntfs_create_inode(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *dentry, const struct cpu_str *uni,
+		      umode_t mode, dev_t dev, const char *symname, u32 size,
+		      struct ntfs_fnd *fnd)
 {
 	int err;
 	struct super_block *sb = dir->i_sb;

@@ -1680,14 +1679,13 @@ struct inode *ntfs_create_inode(struct user_namespace *mnt_userns,
 	kfree(rp);
 
 out1:
-	if (err) {
+	if (err)
 		ni_unlock(dir_ni);
-		return ERR_PTR(err);
-	}
 
-	unlock_new_inode(inode);
+	if (!err)
+		unlock_new_inode(inode);
 
-	return inode;
+	return err;
 }
 
 int ntfs_link_inode(struct inode *inode, struct dentry *dentry)

fs/ntfs3/namei.c +8 ~~-23~~

index 7b7634b38eea8..c5b15f70e5f02 100644
@@ -105,12 +105,8 @@ static struct dentry *ntfs_lookup(struct inode *dir, struct dentry *dentry,
 static int ntfs_create(struct user_namespace *mnt_userns, struct inode *dir,
 		       struct dentry *dentry, umode_t mode, bool excl)
 {
-	struct inode *inode;
-
-	inode = ntfs_create_inode(mnt_userns, dir, dentry, NULL, S_IFREG | mode,
-				  0, NULL, 0, NULL);
-
-	return IS_ERR(inode) ? PTR_ERR(inode) : 0;
+	return ntfs_create_inode(mnt_userns, dir, dentry, NULL, S_IFREG | mode,
+				 0, NULL, 0, NULL);
 }
 
 /*

@@ -121,12 +117,8 @@ static int ntfs_create(struct user_namespace *mnt_userns, struct inode *dir,
 static int ntfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 		      struct dentry *dentry, umode_t mode, dev_t rdev)
 {
-	struct inode *inode;
-
-	inode = ntfs_create_inode(mnt_userns, dir, dentry, NULL, mode, rdev,
-				  NULL, 0, NULL);
-
-	return IS_ERR(inode) ? PTR_ERR(inode) : 0;
+	return ntfs_create_inode(mnt_userns, dir, dentry, NULL, mode, rdev,
+				 NULL, 0, NULL);
 }
 
 /*

@@ -195,12 +187,9 @@ static int ntfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 			struct dentry *dentry, const char *symname)
 {
 	u32 size = strlen(symname);
-	struct inode *inode;
-
-	inode = ntfs_create_inode(mnt_userns, dir, dentry, NULL, S_IFLNK | 0777,
-				  0, symname, size, NULL);
 
-	return IS_ERR(inode) ? PTR_ERR(inode) : 0;
+	return ntfs_create_inode(mnt_userns, dir, dentry, NULL, S_IFLNK | 0777,
+				 0, symname, size, NULL);
 }
 
 /*

@@ -209,12 +198,8 @@ static int ntfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 static int ntfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 		      struct dentry *dentry, umode_t mode)
 {
-	struct inode *inode;
-
-	inode = ntfs_create_inode(mnt_userns, dir, dentry, NULL, S_IFDIR | mode,
-				  0, NULL, 0, NULL);
-
-	return IS_ERR(inode) ? PTR_ERR(inode) : 0;
+	return ntfs_create_inode(mnt_userns, dir, dentry, NULL, S_IFDIR | mode,
+				 0, NULL, 0, NULL);
 }
 
 /*

fs/ntfs3/ntfs_fs.h +4 -5

index 482958c016444..856fe8673fe71 100644
@@ -708,11 +708,10 @@ int ntfs_sync_inode(struct inode *inode);
 int ntfs_flush_inodes(struct super_block *sb, struct inode *i1,
 		      struct inode *i2);
 int inode_write_data(struct inode *inode, const void *data, size_t bytes);
-struct inode *ntfs_create_inode(struct user_namespace *mnt_userns,
-				struct inode *dir, struct dentry *dentry,
-				const struct cpu_str *uni, umode_t mode,
-				dev_t dev, const char *symname, u32 size,
-				struct ntfs_fnd *fnd);
+int ntfs_create_inode(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *dentry, const struct cpu_str *uni,
+		      umode_t mode, dev_t dev, const char *symname, u32 size,
+		      struct ntfs_fnd *fnd);
 int ntfs_link_inode(struct inode *inode, struct dentry *dentry);
 int ntfs_unlink_inode(struct inode *dir, const struct dentry *dentry);
 void ntfs_evict_inode(struct inode *inode);

Signature · 1 line

2.53.0