Message-Id: <20201128213527.2669807-34-christian.brauner@ubuntu.com>
Date:   Sat, 28 Nov 2020 22:35:22 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        linux-fsdevel@...r.kernel.org
Cc:     John Johansen <john.johansen@...onical.com>,
        James Morris <jmorris@...ei.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Geoffrey Thomas <geofft@...reload.com>,
        Mrunal Patel <mpatel@...hat.com>,
        Josh Triplett <josh@...htriplett.org>,
        Andy Lutomirski <luto@...nel.org>,
        Theodore Tso <tytso@....edu>, Alban Crequy <alban@...volk.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Howells <dhowells@...hat.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Lennart Poettering <lennart@...ttering.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>, smbarber@...omium.org,
        Phil Estes <estesp@...il.com>, Serge Hallyn <serge@...lyn.com>,
        Kees Cook <keescook@...omium.org>,
        Todd Kjos <tkjos@...gle.com>, Paul Moore <paul@...l-moore.com>,
        Jonathan Corbet <corbet@....net>,
        containers@...ts.linux-foundation.org, fstests@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-api@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH v3 33/38] ext4: support idmapped mounts

This enables ext4 to support idmapped mounts. All dedicated helpers we need for
this exist. The vfs will have already made sure that the fsids can be translated
after having been shifted if they are on an idmapped mount.

This implements helpers for the new inode operations that we've added. The core
change is the allocation of a new inode based on the mount's user namespace.
Code duplication is virtually non-existent because we can implement the
non-idmapped mount aware inode methods on top of the idmapped mount aware inode
methods. If the initial user namespace is passed nothing changes so non-idmapped
mounts will see identical behavior as before.

It is also noteworthy that the idmapped mount implementation allows us to
cleanly handle ioctls() too. I've kept this as a single patch for now since the
change is overall fairly mechanical but I'm happy to split this.

Let's create simple example where we idmap an ext4 filesystem:

 root@...vm:~# truncate -s 5G ext4.img

 root@...vm:~# mkfs.ext4 ./ext4.img
 mke2fs 1.45.5 (07-Jan-2020)
 Discarding device blocks: done
 Creating filesystem with 1310720 4k blocks and 327680 inodes
 Filesystem UUID: 3fd91794-c6ca-4b0f-9964-289a000919cf
 Superblock backups stored on blocks:
         32768, 98304, 163840, 229376, 294912, 819200, 884736

 Allocating group tables: done
 Writing inode tables: done
 Creating journal (16384 blocks): done
 Writing superblocks and filesystem accounting information: done

 root@...vm:~# losetup -f --show ./ext4.img
 /dev/loop0

 root@...vm:~# mount /dev/loop0 /mnt

 root@...vm:~# ls -al /mnt/
 total 24
 drwxr-xr-x  3 root root  4096 Oct 28 13:34 .
 drwxr-xr-x 30 root root  4096 Oct 28 13:22 ..
 drwx------  2 root root 16384 Oct 28 13:34 lost+found

 # Let's create an idmapped mount at /idmapped1 where we map uid and gid 0 to
 # uid and gid 1000
 root@...vm:/# ./mount2 -mb:0:1000:1 /mnt/ /idmapped1/

 root@...vm:/# ls -al /idmapped1/
 total 24
 drwxr-xr-x  3 ubuntu ubuntu  4096 Oct 28 13:34 .
 drwxr-xr-x 30 root   root    4096 Oct 28 13:22 ..
 drwx------  2 ubuntu ubuntu 16384 Oct 28 13:34 lost+found

 # Let's create an idmapped mount at /idmapped2 where we map uid and gid 0 to
 # uid and gid 2000
 root@...vm:/# ./mount2 -mb:0:2000:1 /mnt/ /idmapped2/

 root@...vm:/# ls -al /idmapped2/
 total 24
 drwxr-xr-x  3 2000 2000  4096 Oct 28 13:34 .
 drwxr-xr-x 31 root root  4096 Oct 28 13:39 ..
 drwx------  2 2000 2000 16384 Oct 28 13:34 lost+found

Let's create another example where we idmap the rootfs filesystem without a
mapping for uid 0 and gid 0:

 # Create an idmapped mount of for a full POSIX range of rootfs under /mnt
 # but without a mapping for uid 0 to reduce attack surface

 root@...vm:/# ./mount2 -mb:1:1:65536 / /mnt/

 # Since we don't have a mapping for uid and gid 0 all files owned by uid and
 # gid 0 should show up as uid and gid 65534:
 root@...vm:/# ls -al /mnt/
 total 664
 drwxr-xr-x 31 nobody nogroup   4096 Oct 28 13:39 .
 drwxr-xr-x 31 root   root      4096 Oct 28 13:39 ..
 lrwxrwxrwx  1 nobody nogroup      7 Aug 25 07:44 bin -> usr/bin
 drwxr-xr-x  4 nobody nogroup   4096 Oct 28 13:17 boot
 drwxr-xr-x  2 nobody nogroup   4096 Aug 25 07:48 dev
 drwxr-xr-x 81 nobody nogroup   4096 Oct 28 04:00 etc
 drwxr-xr-x  4 nobody nogroup   4096 Oct 28 04:00 home
 lrwxrwxrwx  1 nobody nogroup      7 Aug 25 07:44 lib -> usr/lib
 lrwxrwxrwx  1 nobody nogroup      9 Aug 25 07:44 lib32 -> usr/lib32
 lrwxrwxrwx  1 nobody nogroup      9 Aug 25 07:44 lib64 -> usr/lib64
 lrwxrwxrwx  1 nobody nogroup     10 Aug 25 07:44 libx32 -> usr/libx32
 drwx------  2 nobody nogroup  16384 Aug 25 07:47 lost+found
 drwxr-xr-x  2 nobody nogroup   4096 Aug 25 07:44 media
 drwxr-xr-x 31 nobody nogroup   4096 Oct 28 13:39 mnt
 drwxr-xr-x  2 nobody nogroup   4096 Aug 25 07:44 opt
 drwxr-xr-x  2 nobody nogroup   4096 Apr 15  2020 proc
 drwx--x--x  6 nobody nogroup   4096 Oct 28 13:34 root
 drwxr-xr-x  2 nobody nogroup   4096 Aug 25 07:46 run
 lrwxrwxrwx  1 nobody nogroup      8 Aug 25 07:44 sbin -> usr/sbin
 drwxr-xr-x  2 nobody nogroup   4096 Aug 25 07:44 srv
 drwxr-xr-x  2 nobody nogroup   4096 Apr 15  2020 sys
 drwxrwxrwt 10 nobody nogroup   4096 Oct 28 13:19 tmp
 drwxr-xr-x 14 nobody nogroup   4096 Oct 20 13:00 usr
 drwxr-xr-x 12 nobody nogroup   4096 Aug 25 07:45 var

 # Since we do have a mapping for uid and gid 1000 all files owned by uid and
 # gid 1000 should simply show up as uid and gid 1000:
 root@...vm:/# ls -al /mnt/home/ubuntu/
 total 40
 drwxr-xr-x 3 ubuntu ubuntu  4096 Oct 28 00:43 .
 drwxr-xr-x 4 nobody nogroup 4096 Oct 28 04:00 ..
 -rw------- 1 ubuntu ubuntu  2936 Oct 28 12:26 .bash_history
 -rw-r--r-- 1 ubuntu ubuntu   220 Feb 25  2020 .bash_logout
 -rw-r--r-- 1 ubuntu ubuntu  3771 Feb 25  2020 .bashrc
 -rw-r--r-- 1 ubuntu ubuntu   807 Feb 25  2020 .profile
 -rw-r--r-- 1 ubuntu ubuntu     0 Oct 16 16:11 .sudo_as_admin_successful
 -rw------- 1 ubuntu ubuntu  1144 Oct 28 00:43 .viminfo

Cc: Christoph Hellwig <hch@....de>
Cc: David Howells <dhowells@...hat.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: linux-fsdevel@...r.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
---
/* v2 */
unchanged

/* v3 */
unchanged
---
 fs/ext4/Kconfig  |  9 +++++++++
 fs/ext4/acl.c    |  2 +-
 fs/ext4/ext4.h   | 13 +++++++------
 fs/ext4/ialloc.c |  7 ++++---
 fs/ext4/inode.c  | 11 +++++++----
 fs/ext4/ioctl.c  | 18 ++++++++++--------
 fs/ext4/namei.c  | 30 ++++++++++++++++--------------
 fs/ext4/super.c  |  6 +++++-
 8 files changed, 59 insertions(+), 37 deletions(-)

diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index 619dd35ddd48..5918c05cfe5b 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig
@@ -118,3 +118,12 @@ config EXT4_KUNIT_TESTS
 	  to the KUnit documentation in Documentation/dev-tools/kunit/.
 
 	  If unsure, say N.
+
+config EXT4_IDMAP_MOUNTS
+	bool "Support vfs idmapped mounts in ext4"
+	depends on EXT4_FS
+	default n
+	help
+	  The vfs allows to expose a filesystem at different mountpoints with
+	  differnet idmappings. Allow ext4 to be exposed through idmapped
+	  mounts.
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 3ab0a69b974b..7c413bd4d2f2 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -246,7 +246,7 @@ ext4_set_acl(struct user_namespace *user_ns, struct inode *inode,
 	ext4_fc_start_update(inode);
 
 	if ((type == ACL_TYPE_ACCESS) && acl) {
-		error = posix_acl_update_mode(&init_user_ns, inode, &mode, &acl);
+		error = posix_acl_update_mode(user_ns, inode, &mode, &acl);
 		if (error)
 			goto out_stop;
 		if (mode != inode->i_mode)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b89efd36ea7e..bf6c92794480 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2724,18 +2724,19 @@ extern int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
 
 /* ialloc.c */
 extern int ext4_mark_inode_used(struct super_block *sb, int ino);
-extern struct inode *__ext4_new_inode(handle_t *, struct inode *, umode_t,
+extern struct inode *__ext4_new_inode(struct user_namespace *, handle_t *,
+				      struct inode *, umode_t,
 				      const struct qstr *qstr, __u32 goal,
 				      uid_t *owner, __u32 i_flags,
 				      int handle_type, unsigned int line_no,
 				      int nblocks);
 
-#define ext4_new_inode(handle, dir, mode, qstr, goal, owner, i_flags) \
-	__ext4_new_inode((handle), (dir), (mode), (qstr), (goal), (owner), \
-			 i_flags, 0, 0, 0)
-#define ext4_new_inode_start_handle(dir, mode, qstr, goal, owner, \
+#define ext4_new_inode(handle, dir, mode, qstr, goal, owner, i_flags)          \
+	__ext4_new_inode(&init_user_ns, (handle), (dir), (mode), (qstr),       \
+			 (goal), (owner), i_flags, 0, 0, 0)
+#define ext4_new_inode_start_handle(user_ns, dir, mode, qstr, goal, owner, \
 				    type, nblocks)		    \
-	__ext4_new_inode(NULL, (dir), (mode), (qstr), (goal), (owner), \
+	__ext4_new_inode((user_ns), NULL, (dir), (mode), (qstr), (goal), (owner), \
 			 0, (type), __LINE__, (nblocks))
 
 
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index d91f69282311..93251687c6a2 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -919,7 +919,8 @@ static int ext4_xattr_credits_for_new_inode(struct inode *dir, mode_t mode,
  * For other inodes, search forward from the parent directory's block
  * group to find a free inode.
  */
-struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
+struct inode *__ext4_new_inode(struct user_namespace *user_ns,
+			       handle_t *handle, struct inode *dir,
 			       umode_t mode, const struct qstr *qstr,
 			       __u32 goal, uid_t *owner, __u32 i_flags,
 			       int handle_type, unsigned int line_no,
@@ -969,10 +970,10 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
 		i_gid_write(inode, owner[1]);
 	} else if (test_opt(sb, GRPID)) {
 		inode->i_mode = mode;
-		inode->i_uid = current_fsuid();
+		inode->i_uid = fsuid_into_mnt(user_ns);
 		inode->i_gid = dir->i_gid;
 	} else
-		inode_init_owner(inode, &init_user_ns, dir, mode);
+		inode_init_owner(inode, user_ns, dir, mode);
 
 	if (ext4_has_feature_project(sb) &&
 	    ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT))
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a1a4a00ecfa0..0bbedb8070d9 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -20,6 +20,7 @@
  */
 
 #include <linux/fs.h>
+#include <linux/mount.h>
 #include <linux/time.h>
 #include <linux/highuid.h>
 #include <linux/pagemap.h>
@@ -5325,7 +5326,7 @@ int ext4_setattr(struct user_namespace *user_ns, struct dentry *dentry,
 				  ATTR_GID | ATTR_TIMES_SET))))
 		return -EPERM;
 
-	error = setattr_prepare(&init_user_ns, dentry, attr);
+	error = setattr_prepare(user_ns, dentry, attr);
 	if (error)
 		return error;
 
@@ -5500,7 +5501,7 @@ int ext4_setattr(struct user_namespace *user_ns, struct dentry *dentry,
 	}
 
 	if (!error) {
-		setattr_copy(&init_user_ns, inode, attr);
+		setattr_copy(user_ns, inode, attr);
 		mark_inode_dirty(inode);
 	}
 
@@ -5512,7 +5513,7 @@ int ext4_setattr(struct user_namespace *user_ns, struct dentry *dentry,
 		ext4_orphan_del(NULL, inode);
 
 	if (!error && (ia_valid & ATTR_MODE))
-		rc = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
+		rc = posix_acl_chmod(user_ns, inode, inode->i_mode);
 
 err_out:
 	if  (error)
@@ -5526,6 +5527,7 @@ int ext4_setattr(struct user_namespace *user_ns, struct dentry *dentry,
 int ext4_getattr(const struct path *path, struct kstat *stat,
 		 u32 request_mask, unsigned int query_flags)
 {
+	struct user_namespace *user_ns;
 	struct inode *inode = d_inode(path->dentry);
 	struct ext4_inode *raw_inode;
 	struct ext4_inode_info *ei = EXT4_I(inode);
@@ -5559,7 +5561,8 @@ int ext4_getattr(const struct path *path, struct kstat *stat,
 				  STATX_ATTR_NODUMP |
 				  STATX_ATTR_VERITY);
 
-	generic_fillattr(&init_user_ns, inode, stat);
+	user_ns = mnt_user_ns(path->mnt);
+	generic_fillattr(user_ns, inode, stat);
 	return 0;
 }
 
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index e35aba820254..6fff34587f0b 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -111,6 +111,7 @@ void ext4_reset_inode_seed(struct inode *inode)
  *
  */
 static long swap_inode_boot_loader(struct super_block *sb,
+				struct user_namespace *user_ns,
 				struct inode *inode)
 {
 	handle_t *handle;
@@ -139,7 +140,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
 	}
 
 	if (IS_RDONLY(inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
-	    !inode_owner_or_capable(&init_user_ns, inode) || !capable(CAP_SYS_ADMIN)) {
+	    !inode_owner_or_capable(user_ns, inode) || !capable(CAP_SYS_ADMIN)) {
 		err = -EPERM;
 		goto journal_err_out;
 	}
@@ -814,6 +815,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	struct inode *inode = file_inode(filp);
 	struct super_block *sb = inode->i_sb;
 	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct user_namespace *user_ns = mnt_user_ns(filp->f_path.mnt);
 	unsigned int flags;
 
 	ext4_debug("cmd = %u, arg = %lu\n", cmd, arg);
@@ -829,7 +831,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case FS_IOC_SETFLAGS: {
 		int err;
 
-		if (!inode_owner_or_capable(&init_user_ns, inode))
+		if (!inode_owner_or_capable(user_ns, inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
@@ -871,7 +873,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		__u32 generation;
 		int err;
 
-		if (!inode_owner_or_capable(&init_user_ns, inode))
+		if (!inode_owner_or_capable(user_ns, inode))
 			return -EPERM;
 
 		if (ext4_has_metadata_csum(inode->i_sb)) {
@@ -1010,7 +1012,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_MIGRATE:
 	{
 		int err;
-		if (!inode_owner_or_capable(&init_user_ns, inode))
+		if (!inode_owner_or_capable(user_ns, inode))
 			return -EACCES;
 
 		err = mnt_want_write_file(filp);
@@ -1032,7 +1034,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_ALLOC_DA_BLKS:
 	{
 		int err;
-		if (!inode_owner_or_capable(&init_user_ns, inode))
+		if (!inode_owner_or_capable(user_ns, inode))
 			return -EACCES;
 
 		err = mnt_want_write_file(filp);
@@ -1051,7 +1053,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		err = mnt_want_write_file(filp);
 		if (err)
 			return err;
-		err = swap_inode_boot_loader(sb, inode);
+		err = swap_inode_boot_loader(sb, user_ns, inode);
 		mnt_drop_write_file(filp);
 		return err;
 	}
@@ -1214,7 +1216,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 
 	case EXT4_IOC_CLEAR_ES_CACHE:
 	{
-		if (!inode_owner_or_capable(&init_user_ns, inode))
+		if (!inode_owner_or_capable(user_ns, inode))
 			return -EACCES;
 		ext4_clear_inode_es(inode);
 		return 0;
@@ -1260,7 +1262,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			return -EFAULT;
 
 		/* Make sure caller has proper permission */
-		if (!inode_owner_or_capable(&init_user_ns, inode))
+		if (!inode_owner_or_capable(user_ns, inode))
 			return -EACCES;
 
 		if (fa.fsx_xflags & ~EXT4_SUPPORTED_FS_XFLAGS)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 194bc37fba55..f76d2f730366 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2616,8 +2616,8 @@ static int ext4_create(struct user_namespace *user_ns, struct inode *dir,
 	credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
 retry:
-	inode = ext4_new_inode_start_handle(dir, mode, &dentry->d_name, 0,
-					    NULL, EXT4_HT_DIR, credits);
+	inode = ext4_new_inode_start_handle(user_ns, dir, mode, &dentry->d_name,
+					    0, NULL, EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
 	err = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
@@ -2651,8 +2651,8 @@ static int ext4_mknod(struct user_namespace *user_ns, struct inode *dir,
 	credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
 retry:
-	inode = ext4_new_inode_start_handle(dir, mode, &dentry->d_name, 0,
-					    NULL, EXT4_HT_DIR, credits);
+	inode = ext4_new_inode_start_handle(user_ns, dir, mode, &dentry->d_name,
+					    0, NULL, EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
 	err = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
@@ -2683,7 +2683,7 @@ static int ext4_tmpfile(struct user_namespace *user_ns, struct inode *dir,
 		return err;
 
 retry:
-	inode = ext4_new_inode_start_handle(dir, mode,
+	inode = ext4_new_inode_start_handle(user_ns, dir, mode,
 					    NULL, 0, NULL,
 					    EXT4_HT_DIR,
 			EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
@@ -2798,7 +2798,7 @@ static int ext4_mkdir(struct user_namespace *user_ns, struct inode *dir,
 	credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
 		   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
 retry:
-	inode = ext4_new_inode_start_handle(dir, S_IFDIR | mode,
+	inode = ext4_new_inode_start_handle(user_ns, dir, S_IFDIR | mode,
 					    &dentry->d_name,
 					    0, NULL, EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
@@ -3335,7 +3335,7 @@ static int ext4_symlink(struct user_namespace *user_ns, struct inode *dir,
 			  EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3;
 	}
 
-	inode = ext4_new_inode_start_handle(dir, S_IFLNK|S_IRWXUGO,
+	inode = ext4_new_inode_start_handle(user_ns, dir, S_IFLNK|S_IRWXUGO,
 					    &dentry->d_name, 0, NULL,
 					    EXT4_HT_DIR, credits);
 	handle = ext4_journal_current_handle();
@@ -3667,7 +3667,8 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
 	}
 }
 
-static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
+static struct inode *ext4_whiteout_for_rename(struct user_namespace *user_ns,
+					      struct ext4_renament *ent,
 					      int credits, handle_t **h)
 {
 	struct inode *wh;
@@ -3681,7 +3682,8 @@ static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
 	credits += (EXT4_MAXQUOTAS_TRANS_BLOCKS(ent->dir->i_sb) +
 		    EXT4_XATTR_TRANS_BLOCKS + 4);
 retry:
-	wh = ext4_new_inode_start_handle(ent->dir, S_IFCHR | WHITEOUT_MODE,
+	wh = ext4_new_inode_start_handle(user_ns, ent->dir,
+					 S_IFCHR | WHITEOUT_MODE,
 					 &ent->dentry->d_name, 0, NULL,
 					 EXT4_HT_DIR, credits);
 
@@ -3708,9 +3710,9 @@ static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
  * while new_{dentry,inode) refers to the destination dentry/inode
  * This comes from rename(const char *oldpath, const char *newpath)
  */
-static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
-		       struct inode *new_dir, struct dentry *new_dentry,
-		       unsigned int flags)
+static int ext4_rename(struct user_namespace *user_ns, struct inode *old_dir,
+		       struct dentry *old_dentry, struct inode *new_dir,
+		       struct dentry *new_dentry, unsigned int flags)
 {
 	handle_t *handle = NULL;
 	struct ext4_renament old = {
@@ -3794,7 +3796,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 			goto end_rename;
 		}
 	} else {
-		whiteout = ext4_whiteout_for_rename(&old, credits, &handle);
+		whiteout = ext4_whiteout_for_rename(user_ns, &old, credits, &handle);
 		if (IS_ERR(whiteout)) {
 			retval = PTR_ERR(whiteout);
 			whiteout = NULL;
@@ -4108,7 +4110,7 @@ static int ext4_rename2(struct user_namespace *user_ns, struct inode *old_dir,
 					 new_dir, new_dentry);
 	}
 
-	return ext4_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
+	return ext4_rename(user_ns, old_dir, old_dentry, new_dir, new_dentry, flags);
 }
 
 /*
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6633b20224d5..6420bd1d569a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5008,7 +5008,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	}
 
 	block = ext4_count_free_clusters(sb);
-	ext4_free_blocks_count_set(sbi->s_es, 
+	ext4_free_blocks_count_set(sbi->s_es,
 				   EXT4_C2B(sbi, block));
 	ext4_superblock_csum_set(sb);
 	err = percpu_counter_init(&sbi->s_freeclusters_counter, block,
@@ -6631,7 +6631,11 @@ static struct file_system_type ext4_fs_type = {
 	.name		= "ext4",
 	.mount		= ext4_mount,
 	.kill_sb	= kill_block_super,
+#ifdef CONFIG_EXT4_IDMAP_MOUNTS
+	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
+#else
 	.fs_flags	= FS_REQUIRES_DEV,
+#endif
 };
 MODULE_ALIAS_FS("ext4");
 
-- 
2.29.2

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