inode: make init and permission helpers idmapped mount aware

The inode_owner_or_capable() helper determines whether the caller is the
owner of the inode or is capable with respect to that inode. Allow it to
handle idmapped mounts. If the inode is accessed through an idmapped
mount it according to the mount's user namespace. Afterwards the checks
are identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Similarly, allow the inode_init_owner() helper to handle idmapped
mounts. It initializes a new inode on idmapped mounts by mapping the
fsuid and fsgid of the caller from the mount's user namespace. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

54 files changed, 112 insertions, 91 deletions

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 6261719f6f2a..d77b28e8d57a 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -258,7 +258,7 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
 
 	if (S_ISLNK(inode->i_mode))
 		return -EOPNOTSUPP;
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 	if (value) {
 		/* update the cached acl value */
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 4a937fac1acb..f66eb3c12c8a 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -251,7 +251,7 @@ int v9fs_init_inode(struct v9fs_session_info *v9ses,
 {
 	int err = 0;
 
-	inode_init_owner(inode, NULL, mode);
+	inode_init_owner(&init_user_ns,inode,  NULL, mode);
 	inode->i_blocks = 0;
 	inode->i_rdev = rdev;
 	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
diff --git a/fs/attr.c b/fs/attr.c
index c9e29e589cec..00ae0b000146 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -87,7 +87,7 @@ int setattr_prepare(struct dentry *dentry, struct iattr *attr)
 
 	/* Make sure a caller can chmod. */
 	if (ia_valid & ATTR_MODE) {
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EPERM;
 		/* Also check the setgid bit! */
 		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
@@ -98,7 +98,7 @@ int setattr_prepare(struct dentry *dentry, struct iattr *attr)
 
 	/* Check for setting the inode time. */
 	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EPERM;
 	}
 
@@ -243,7 +243,7 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de
 		if (IS_IMMUTABLE(inode))
 			return -EPERM;
 
-		if (!inode_owner_or_capable(inode)) {
+		if (!inode_owner_or_capable(&init_user_ns, inode)) {
 			error = inode_permission(&init_user_ns, inode,
 						 MAY_WRITE);
 			if (error)
diff --git a/fs/bfs/dir.c b/fs/bfs/dir.c
index d8dfe3a0cb39..be1335a8d25b 100644
--- a/fs/bfs/dir.c
+++ b/fs/bfs/dir.c
@@ -96,7 +96,7 @@ static int bfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 	}
 	set_bit(ino, info->si_imap);
 	info->si_freei--;
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 	inode->i_blocks = 0;
 	inode->i_op = &bfs_file_inops;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 512ee2650bbb..07fe8b2f3bab 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6190,7 +6190,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	if (ret != 0)
 		goto fail_unlock;
 
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode_set_bytes(inode, 0);
 
 	inode->i_mtime = current_time(inode);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8ced6dfefee4..1f763c60415b 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -213,7 +213,7 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 	const char *comp = NULL;
 	u32 binode_flags;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	if (btrfs_root_readonly(root))
@@ -429,7 +429,7 @@ static int btrfs_ioctl_fssetxattr(struct file *file, void __user *arg)
 	unsigned old_i_flags;
 	int ret = 0;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	if (btrfs_root_readonly(root))
@@ -1862,7 +1862,7 @@ static noinline int __btrfs_ioctl_snap_create(struct file *file,
 			btrfs_info(BTRFS_I(file_inode(file))->root->fs_info,
 				   "Snapshot src from another FS");
 			ret = -EXDEV;
-		} else if (!inode_owner_or_capable(src_inode)) {
+		} else if (!inode_owner_or_capable(&init_user_ns, src_inode)) {
 			/*
 			 * Subvolume creation is not restricted, but snapshots
 			 * are limited to own subvolumes only
@@ -1982,7 +1982,7 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
 	u64 flags;
 	int ret = 0;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	ret = mnt_want_write_file(file);
@@ -4453,7 +4453,7 @@ static long _btrfs_ioctl_set_received_subvol(struct file *file,
 	int ret = 0;
 	int received_uuid_changed;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	ret = mnt_want_write_file(file);
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index 6bd97bd4cb37..3a4099a2bf05 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -62,7 +62,7 @@ struct inode *btrfs_new_test_inode(void)
 	BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
 	BTRFS_I(inode)->location.objectid = BTRFS_FIRST_FREE_OBJECTID;
 	BTRFS_I(inode)->location.offset = 0;
-	inode_init_owner(inode, NULL, S_IFREG);
+	inode_init_owner(&init_user_ns, inode, NULL, S_IFREG);
 
 	return inode;
 }
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index a51cef6bd27f..ed3d623724cd 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -465,7 +465,7 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 		return -EFAULT;
 	policy.version = version;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(filp);
diff --git a/fs/efivarfs/file.c b/fs/efivarfs/file.c
index feaa5e182b7b..e6bc0302643b 100644
--- a/fs/efivarfs/file.c
+++ b/fs/efivarfs/file.c
@@ -137,7 +137,7 @@ efivarfs_ioc_setxflags(struct file *file, void __user *arg)
 	unsigned int oldflags = efivarfs_getflags(inode);
 	int error;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	if (copy_from_user(&flags, arg, sizeof(flags)))
diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index 432c3febea6d..df14e750e9fe 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c
@@ -551,7 +551,7 @@ got:
 		inode->i_uid = current_fsuid();
 		inode->i_gid = dir->i_gid;
 	} else
-		inode_init_owner(inode, dir, mode);
+		inode_init_owner(&init_user_ns, inode, dir, mode);
 
 	inode->i_ino = ino;
 	inode->i_blocks = 0;
diff --git a/fs/ext2/ioctl.c b/fs/ext2/ioctl.c
index 32a8d10b579d..b399cbb7022d 100644
--- a/fs/ext2/ioctl.c
+++ b/fs/ext2/ioctl.c
@@ -39,7 +39,7 @@ long ext2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (ret)
 			return ret;
 
-		if (!inode_owner_or_capable(inode)) {
+		if (!inode_owner_or_capable(&init_user_ns, inode)) {
 			ret = -EACCES;
 			goto setflags_out;
 		}
@@ -84,7 +84,7 @@ setflags_out:
 	case EXT2_IOC_SETVERSION: {
 		__u32 generation;
 
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EPERM;
 		ret = mnt_want_write_file(filp);
 		if (ret)
@@ -117,7 +117,7 @@ setversion_out:
 		if (!test_opt(inode->i_sb, RESERVATION) ||!S_ISREG(inode->i_mode))
 			return -ENOTTY;
 
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 
 		if (get_user(rsv_window_size, (int __user *)arg))
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index b215c564bc31..00c1ec6eee16 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -972,7 +972,7 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
 		inode->i_uid = current_fsuid();
 		inode->i_gid = dir->i_gid;
 	} else
-		inode_init_owner(inode, dir, mode);
+		inode_init_owner(&init_user_ns, inode, dir, mode);
 
 	if (ext4_has_feature_project(sb) &&
 	    ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT))
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index d9665d2f82db..ab80e2493fdc 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -139,7 +139,8 @@ static long swap_inode_boot_loader(struct super_block *sb,
 	}
 
 	if (IS_RDONLY(inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
-	    !inode_owner_or_capable(inode) || !capable(CAP_SYS_ADMIN)) {
+	    !inode_owner_or_capable(&init_user_ns, inode) ||
+	    !capable(CAP_SYS_ADMIN)) {
 		err = -EPERM;
 		goto journal_err_out;
 	}
@@ -829,7 +830,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case FS_IOC_SETFLAGS: {
 		int err;
 
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
@@ -871,7 +872,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		__u32 generation;
 		int err;
 
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EPERM;
 
 		if (ext4_has_metadata_csum(inode->i_sb)) {
@@ -1010,7 +1011,7 @@ mext_out:
 	case EXT4_IOC_MIGRATE:
 	{
 		int err;
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 
 		err = mnt_want_write_file(filp);
@@ -1032,7 +1033,7 @@ mext_out:
 	case EXT4_IOC_ALLOC_DA_BLKS:
 	{
 		int err;
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 
 		err = mnt_want_write_file(filp);
@@ -1217,7 +1218,7 @@ resizefs_out:
 
 	case EXT4_IOC_CLEAR_ES_CACHE:
 	{
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 		ext4_clear_inode_es(inode);
 		return 0;
@@ -1263,7 +1264,7 @@ resizefs_out:
 			return -EFAULT;
 
 		/* Make sure caller has proper permission */
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 
 		if (fa.fsx_xflags & ~EXT4_SUPPORTED_FS_XFLAGS)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f585545277d7..5fc0ff28b5dd 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1961,7 +1961,7 @@ static int f2fs_ioc_setflags(struct file *filp, unsigned long arg)
 	u32 iflags;
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	if (get_user(fsflags, (int __user *)arg))
@@ -2008,7 +2008,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	if (!S_ISREG(inode->i_mode))
@@ -2075,7 +2075,7 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(filp);
@@ -2117,7 +2117,7 @@ static int f2fs_ioc_start_volatile_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	if (!S_ISREG(inode->i_mode))
@@ -2152,7 +2152,7 @@ static int f2fs_ioc_release_volatile_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(filp);
@@ -2181,7 +2181,7 @@ static int f2fs_ioc_abort_volatile_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(filp);
@@ -3158,7 +3158,7 @@ static int f2fs_ioc_fssetxattr(struct file *filp, unsigned long arg)
 		return -EFAULT;
 
 	/* Make sure caller has proper permission */
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	if (fa.fsx_xflags & ~F2FS_SUPPORTED_XFLAGS)
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 6edb1ab579a1..ad98926bacac 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -46,7 +46,7 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t mode)
 
 	nid_free = true;
 
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 
 	inode->i_ino = ino;
 	inode->i_blocks = 0;
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index 65afcc3cc68a..d772bf13a814 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -114,7 +114,7 @@ static int f2fs_xattr_advise_set(const struct xattr_handler *handler,
 	unsigned char old_advise = F2FS_I(inode)->i_advise;
 	unsigned char new_advise;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 	if (value == NULL)
 		return -EINVAL;
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 05b36b28f2e8..74d99731fd43 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -46,7 +46,7 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
 
 	/* O_NOATIME can only be set by the owner or superuser */
 	if ((arg & O_NOATIME) && !(filp->f_flags & O_NOATIME))
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EPERM;
 
 	/* required for strict SunOS emulation */
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index b39b339feddc..1d994bdfffaa 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -238,7 +238,7 @@ static int do_gfs2_set_flags(struct file *filp, u32 reqflags, u32 mask,
 		goto out;
 
 	error = -EACCES;
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		goto out;
 
 	error = 0;
diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
index e3da9e96b835..21357046b039 100644
--- a/fs/hfsplus/inode.c
+++ b/fs/hfsplus/inode.c
@@ -376,7 +376,7 @@ struct inode *hfsplus_new_inode(struct super_block *sb, struct inode *dir,
 		return NULL;
 
 	inode->i_ino = sbi->next_cnid++;
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	set_nlink(inode, 1);
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 
diff --git a/fs/hfsplus/ioctl.c b/fs/hfsplus/ioctl.c
index ce15b9496b77..3edb1926d127 100644
--- a/fs/hfsplus/ioctl.c
+++ b/fs/hfsplus/ioctl.c
@@ -91,7 +91,7 @@ static int hfsplus_ioctl_setflags(struct file *file, int __user *user_flags)
 	if (err)
 		goto out;
 
-	if (!inode_owner_or_capable(inode)) {
+	if (!inode_owner_or_capable(&init_user_ns, inode)) {
 		err = -EACCES;
 		goto out_drop_write;
 	}
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index b5c109703daa..6737929e443c 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -836,7 +836,7 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
 		struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
 
 		inode->i_ino = get_next_ino();
-		inode_init_owner(inode, dir, mode);
+		inode_init_owner(&init_user_ns, inode, dir, mode);
 		lockdep_set_class(&inode->i_mapping->i_mmap_rwsem,
 				&hugetlbfs_i_mmap_rwsem_key);
 		inode->i_mapping->a_ops = &hugetlbfs_aops;
diff --git a/fs/inode.c b/fs/inode.c
index cd40cbf87ce4..a9ac97a27784 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2130,14 +2130,21 @@ EXPORT_SYMBOL(init_special_inode);
 
 /**
  * inode_init_owner - Init uid,gid,mode for new inode according to posix standards
+ * @mnt_userns:	User namespace of the mount the inode was created from
  * @inode: New inode
  * @dir: Directory inode
  * @mode: mode of the new inode
+ *
+ * If the inode has been created through an idmapped mount the user namespace of
+ * the vfsmount must be passed through @mnt_userns. This function will then take
+ * care to map the inode according to @mnt_userns before checking permissions
+ * and initializing i_uid and i_gid. On non-idmapped mounts or if permission
+ * checking is to be performed on the raw inode simply passs init_user_ns.
  */
-void inode_init_owner(struct inode *inode, const struct inode *dir,
-			umode_t mode)
+void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
+		      const struct inode *dir, umode_t mode)
 {
-	inode->i_uid = current_fsuid();
+	inode->i_uid = fsuid_into_mnt(mnt_userns);
 	if (dir && dir->i_mode & S_ISGID) {
 		inode->i_gid = dir->i_gid;
 
@@ -2145,32 +2152,41 @@ void inode_init_owner(struct inode *inode, const struct inode *dir,
 		if (S_ISDIR(mode))
 			mode |= S_ISGID;
 		else if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP) &&
-			 !in_group_p(inode->i_gid) &&
-			 !capable_wrt_inode_uidgid(&init_user_ns, dir,
-						   CAP_FSETID))
+			 !in_group_p(i_gid_into_mnt(mnt_userns, dir)) &&
+			 !capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
 			mode &= ~S_ISGID;
 	} else
-		inode->i_gid = current_fsgid();
+		inode->i_gid = fsgid_into_mnt(mnt_userns);
 	inode->i_mode = mode;
 }
 EXPORT_SYMBOL(inode_init_owner);
 
 /**
  * inode_owner_or_capable - check current task permissions to inode
+ * @mnt_userns:	user namespace of the mount the inode was found from
  * @inode: inode being checked
  *
  * Return true if current either has CAP_FOWNER in a namespace with the
  * inode owner uid mapped, or owns the file.
+ *
+ * If the inode has been found through an idmapped mount the user namespace of
+ * the vfsmount must be passed through @mnt_userns. This function will then take
+ * care to map the inode according to @mnt_userns before checking permissions.
+ * On non-idmapped mounts or if permission checking is to be performed on the
+ * raw inode simply passs init_user_ns.
  */
-bool inode_owner_or_capable(const struct inode *inode)
+bool inode_owner_or_capable(struct user_namespace *mnt_userns,
+			    const struct inode *inode)
 {
+	kuid_t i_uid;
 	struct user_namespace *ns;
 
-	if (uid_eq(current_fsuid(), inode->i_uid))
+	i_uid = i_uid_into_mnt(mnt_userns, inode);
+	if (uid_eq(current_fsuid(), i_uid))
 		return true;
 
 	ns = current_user_ns();
-	if (kuid_has_mapping(ns, inode->i_uid) && ns_capable(ns, CAP_FOWNER))
+	if (kuid_has_mapping(ns, i_uid) && ns_capable(ns, CAP_FOWNER))
 		return true;
 	return false;
 }
diff --git a/fs/jfs/ioctl.c b/fs/jfs/ioctl.c
index 10ee0ecca1a8..2581d4db58ff 100644
--- a/fs/jfs/ioctl.c
+++ b/fs/jfs/ioctl.c
@@ -76,7 +76,7 @@ long jfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (err)
 			return err;
 
-		if (!inode_owner_or_capable(inode)) {
+		if (!inode_owner_or_capable(&init_user_ns, inode)) {
 			err = -EACCES;
 			goto setflags_out;
 		}
diff --git a/fs/jfs/jfs_inode.c b/fs/jfs/jfs_inode.c
index 4cef170630db..59379089e939 100644
--- a/fs/jfs/jfs_inode.c
+++ b/fs/jfs/jfs_inode.c
@@ -64,7 +64,7 @@ struct inode *ialloc(struct inode *parent, umode_t mode)
 		goto fail_put;
 	}
 
-	inode_init_owner(inode, parent, mode);
+	inode_init_owner(&init_user_ns, inode, parent, mode);
 	/*
 	 * New inodes need to save sane values on disk when
 	 * uid & gid mount options are used
diff --git a/fs/minix/bitmap.c b/fs/minix/bitmap.c
index f4e5e5181a14..9115948c624e 100644
--- a/fs/minix/bitmap.c
+++ b/fs/minix/bitmap.c
@@ -252,7 +252,7 @@ struct inode *minix_new_inode(const struct inode *dir, umode_t mode, int *error)
 		iput(inode);
 		return NULL;
 	}
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode->i_ino = j;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 	inode->i_blocks = 0;
diff --git a/fs/namei.c b/fs/namei.c
index d78d74f5f5af..04b001ddade3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1088,7 +1088,8 @@ int may_linkat(struct path *link)
 	/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
 	 * otherwise, it must be a safe source.
 	 */
-	if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
+	if (safe_hardlink_source(inode) ||
+	    inode_owner_or_capable(&init_user_ns, inode))
 		return 0;
 
 	audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
@@ -2940,7 +2941,7 @@ static int may_open(const struct path *path, int acc_mode, int flag)
 	}
 
 	/* O_NOATIME can only be set by the owner or superuser */
-	if (flag & O_NOATIME && !inode_owner_or_capable(inode))
+	if (flag & O_NOATIME && !inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	return 0;
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index b6517220cad5..11225a659736 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -348,7 +348,7 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
 	/* reference count of i_bh inherits from nilfs_mdt_read_block() */
 
 	atomic64_inc(&root->inodes_count);
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode->i_ino = ino;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 07d26f61f22a..b053b40315bf 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -132,7 +132,7 @@ static int nilfs_ioctl_setflags(struct inode *inode, struct file *filp,
 	unsigned int flags, oldflags;
 	int ret;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	if (get_user(flags, (int __user *)argp))
diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 583820ec63e2..37c7d03a6284 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -329,7 +329,7 @@ static struct inode *dlmfs_get_root_inode(struct super_block *sb)
 
 	if (inode) {
 		inode->i_ino = get_next_ino();
-		inode_init_owner(inode, NULL, mode);
+		inode_init_owner(&init_user_ns, inode, NULL, mode);
 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 		inc_nlink(inode);
 
@@ -352,7 +352,7 @@ static struct inode *dlmfs_get_inode(struct inode *parent,
 		return NULL;
 
 	inode->i_ino = get_next_ino();
-	inode_init_owner(inode, parent, mode);
+	inode_init_owner(&init_user_ns, inode, parent, mode);
 	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 
 	ip = DLMFS_I(inode);
diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
index 89984172fc4a..50c9b30ee9f6 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -96,7 +96,7 @@ static int ocfs2_set_inode_attr(struct inode *inode, unsigned flags,
 	}
 
 	status = -EACCES;
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		goto bail_unlock;
 
 	if (!S_ISDIR(inode->i_mode))
diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 2a237ab00453..908b79e1082b 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -198,7 +198,7 @@ static struct inode *ocfs2_get_init_inode(struct inode *dir, umode_t mode)
 	 * callers. */
 	if (S_ISDIR(mode))
 		set_nlink(inode, 2);
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	status = dquot_initialize(inode);
 	if (status)
 		return ERR_PTR(status);
diff --git a/fs/omfs/inode.c b/fs/omfs/inode.c
index ce93ccca8639..2a0e83236c01 100644
--- a/fs/omfs/inode.c
+++ b/fs/omfs/inode.c
@@ -48,7 +48,7 @@ struct inode *omfs_new_inode(struct inode *dir, umode_t mode)
 		goto fail;
 
 	inode->i_ino = new_block;
-	inode_init_owner(inode, NULL, mode);
+	inode_init_owner(&init_user_ns, inode, NULL, mode);
 	inode->i_mapping->a_ops = &omfs_aops;
 
 	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 28a075b5f5b2..98a23353b19a 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -636,7 +636,7 @@ static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 	inode->i_state |= I_CREATING;
 	spin_unlock(&inode->i_lock);
 
-	inode_init_owner(inode, dentry->d_parent->d_inode, mode);
+	inode_init_owner(&init_user_ns, inode, dentry->d_parent->d_inode, mode);
 	attr.mode = inode->i_mode;
 
 	err = ovl_create_or_link(dentry, inode, &attr, false);
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index b2948e7b3210..7d8b84c715b3 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -54,7 +54,7 @@ static struct file *ovl_open_realfile(const struct file *file,
 	if (err) {
 		realfile = ERR_PTR(err);
 	} else {
-		if (!inode_owner_or_capable(realinode))
+		if (!inode_owner_or_capable(&init_user_ns, realinode))
 			flags &= ~O_NOATIME;
 
 		realfile = open_with_fake_path(&file->f_path, flags, realinode,
@@ -520,7 +520,7 @@ static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd,
 	long ret;
 	struct inode *inode = file_inode(file);
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(file);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 88d877787770..3e925deaa19a 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1005,7 +1005,7 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 		goto out_acl_release;
 	}
 	err = -EPERM;
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		goto out_acl_release;
 
 	posix_acl_release(acl);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index de5c2047a0e9..06013b7b1e87 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -484,7 +484,7 @@ struct file *ovl_path_open(struct path *path, int flags)
 		return ERR_PTR(err);
 
 	/* O_NOATIME is an optimization, don't fail if not permitted */
-	if (inode_owner_or_capable(inode))
+	if (inode_owner_or_capable(&init_user_ns, inode))
 		flags |= O_NOATIME;
 
 	return dentry_open(path, flags, current_cred());
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 5d9fe2fb2953..9ce8214bfdac 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -874,7 +874,7 @@ set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)
 
 	if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 		return acl ? -EACCES : 0;
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	if (acl) {
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index ee179a81b3da..3fd4326f36b5 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -67,7 +67,7 @@ struct inode *ramfs_get_inode(struct super_block *sb,
 
 	if (inode) {
 		inode->i_ino = get_next_ino();
-		inode_init_owner(inode, dir, mode);
+		inode_init_owner(&init_user_ns, inode, dir, mode);
 		inode->i_mapping->a_ops = &ramfs_aops;
 		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
 		mapping_set_unevictable(inode->i_mapping);
diff --git a/fs/reiserfs/ioctl.c b/fs/reiserfs/ioctl.c
index adb21bea3d60..4f1cbd930179 100644
--- a/fs/reiserfs/ioctl.c
+++ b/fs/reiserfs/ioctl.c
@@ -59,7 +59,7 @@ long reiserfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			if (err)
 				break;
 
-			if (!inode_owner_or_capable(inode)) {
+			if (!inode_owner_or_capable(&init_user_ns, inode)) {
 				err = -EPERM;
 				goto setflags_out;
 			}
@@ -101,7 +101,7 @@ setflags_out:
 		err = put_user(inode->i_generation, (int __user *)arg);
 		break;
 	case REISERFS_IOC_SETVERSION:
-		if (!inode_owner_or_capable(inode)) {
+		if (!inode_owner_or_capable(&init_user_ns, inode)) {
 			err = -EPERM;
 			break;
 		}
diff --git a/fs/reiserfs/namei.c b/fs/reiserfs/namei.c
index 1594687582f0..a67a7d371725 100644
--- a/fs/reiserfs/namei.c
+++ b/fs/reiserfs/namei.c
@@ -615,7 +615,7 @@ static int new_inode_init(struct inode *inode, struct inode *dir, umode_t mode)
 	 * the quota init calls have to know who to charge the quota to, so
 	 * we have to set uid and gid here
 	 */
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	return dquot_initialize(inode);
 }
 
diff --git a/fs/sysv/ialloc.c b/fs/sysv/ialloc.c
index 6c9801986af6..50df794a3c1f 100644
--- a/fs/sysv/ialloc.c
+++ b/fs/sysv/ialloc.c
@@ -163,7 +163,7 @@ struct inode * sysv_new_inode(const struct inode * dir, umode_t mode)
 	*sbi->s_sb_fic_count = cpu_to_fs16(sbi, count);
 	fs16_add(sbi, sbi->s_sb_total_free_inodes, -1);
 	dirty_sb(sb);
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode->i_ino = fs16_to_cpu(sbi, ino);
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 	inode->i_blocks = 0;
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 9a6b8660425a..694e7714545b 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -94,7 +94,7 @@ struct inode *ubifs_new_inode(struct ubifs_info *c, struct inode *dir,
 	 */
 	inode->i_flags |= S_NOCMTIME;
 
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode->i_mtime = inode->i_atime = inode->i_ctime =
 			 current_time(inode);
 	inode->i_mapping->nrpages = 0;
diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c
index 4363d85a3fd4..2326d5122beb 100644
--- a/fs/ubifs/ioctl.c
+++ b/fs/ubifs/ioctl.c
@@ -155,7 +155,7 @@ long ubifs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		if (IS_RDONLY(inode))
 			return -EROFS;
 
-		if (!inode_owner_or_capable(inode))
+		if (!inode_owner_or_capable(&init_user_ns, inode))
 			return -EACCES;
 
 		if (get_user(flags, (int __user *) arg))
diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
index 84ed23edebfd..2ecf0e87660e 100644
--- a/fs/udf/ialloc.c
+++ b/fs/udf/ialloc.c
@@ -103,7 +103,7 @@ struct inode *udf_new_inode(struct inode *dir, umode_t mode)
 		mutex_unlock(&sbi->s_alloc_mutex);
 	}
 
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	if (UDF_QUERY_FLAG(sb, UDF_FLAG_UID_SET))
 		inode->i_uid = sbi->s_uid;
 	if (UDF_QUERY_FLAG(sb, UDF_FLAG_GID_SET))
diff --git a/fs/ufs/ialloc.c b/fs/ufs/ialloc.c
index 969fd60436d3..7e3e08c0166f 100644
--- a/fs/ufs/ialloc.c
+++ b/fs/ufs/ialloc.c
@@ -289,7 +289,7 @@ cg_found:
 	ufs_mark_sb_dirty(sb);
 
 	inode->i_ino = cg * uspi->s_ipg + bit;
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 	inode->i_blocks = 0;
 	inode->i_generation = 0;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
diff --git a/fs/xattr.c b/fs/xattr.c
index 56151bd9e642..c669922e1bde 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -127,7 +127,8 @@ xattr_permission(struct inode *inode, const char *name, int mask)
 		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
-		    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
+		    (mask & MAY_WRITE) &&
+		    !inode_owner_or_capable(&init_user_ns, inode))
 			return -EPERM;
 	}
 
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 97bd29fc8c43..218e80afc859 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1300,7 +1300,7 @@ xfs_ioctl_setattr_get_trans(
 	 * The user ID of the calling process must be equal to the file owner
 	 * ID, except in cases where the CAP_FSETID capability is applicable.
 	 */
-	if (!inode_owner_or_capable(VFS_I(ip))) {
+	if (!inode_owner_or_capable(&init_user_ns, VFS_I(ip))) {
 		error = -EPERM;
 		goto out_cancel;
 	}
diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index bec47f2d074b..569525ee8f69 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -1223,7 +1223,7 @@ static void zonefs_init_dir_inode(struct inode *parent, struct inode *inode,
 	struct super_block *sb = parent->i_sb;
 
 	inode->i_ino = blkdev_nr_zones(sb->s_bdev->bd_disk) + type + 1;
-	inode_init_owner(inode, parent, S_IFDIR | 0555);
+	inode_init_owner(&init_user_ns, inode, parent, S_IFDIR | 0555);
 	inode->i_op = &zonefs_dir_inode_operations;
 	inode->i_fop = &simple_dir_operations;
 	set_nlink(inode, 2);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a85dfe6962df..2a9d4af6a64d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1762,8 +1762,8 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb)
 	return __sb_start_write_trylock(sb, SB_FREEZE_FS);
 }
 
-
-extern bool inode_owner_or_capable(const struct inode *inode);
+bool inode_owner_or_capable(struct user_namespace *mnt_userns,
+			    const struct inode *inode);
 
 /*
  * VFS helper functions..
@@ -1805,8 +1805,8 @@ extern long compat_ptr_ioctl(struct file *file, unsigned int cmd,
 /*
  * VFS file helper functions.
  */
-extern void inode_init_owner(struct inode *inode, const struct inode *dir,
-			umode_t mode);
+void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
+		      const struct inode *dir, umode_t mode);
 extern bool may_open_dev(const struct path *path);
 
 /*
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index e3226b65f5dc..05b1f51d15e0 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -122,7 +122,7 @@ static struct inode *bpf_get_inode(struct super_block *sb,
 	inode->i_mtime = inode->i_atime;
 	inode->i_ctime = inode->i_atime;
 
-	inode_init_owner(inode, dir, mode);
+	inode_init_owner(&init_user_ns, inode, dir, mode);
 
 	return inode;
 }
diff --git a/mm/madvise.c b/mm/madvise.c
index 175c5582d8a9..d4f5eece9d56 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -539,7 +539,8 @@ static inline bool can_do_pageout(struct vm_area_struct *vma)
 	 * otherwise we'd be including shared non-exclusive mappings, which
 	 * opens a side channel.
 	 */
-	return inode_owner_or_capable(file_inode(vma->vm_file)) ||
+	return inode_owner_or_capable(&init_user_ns,
+				      file_inode(vma->vm_file)) ||
 	       file_permission(vma->vm_file, MAY_WRITE) == 0;
 }
 
diff --git a/mm/mincore.c b/mm/mincore.c
index 7bdb4673f776..9122676b54d6 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -166,7 +166,8 @@ static inline bool can_do_mincore(struct vm_area_struct *vma)
 	 * for writing; otherwise we'd be including shared non-exclusive
 	 * mappings, which opens a side channel.
 	 */
-	return inode_owner_or_capable(file_inode(vma->vm_file)) ||
+	return inode_owner_or_capable(&init_user_ns,
+				      file_inode(vma->vm_file)) ||
 	       file_permission(vma->vm_file, MAY_WRITE) == 0;
 }
 
diff --git a/mm/shmem.c b/mm/shmem.c
index 7c6b6d8f6c39..1c68c9edba5e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2303,7 +2303,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 	inode = new_inode(sb);
 	if (inode) {
 		inode->i_ino = ino;
-		inode_init_owner(inode, dir, mode);
+		inode_init_owner(&init_user_ns, inode, dir, mode);
 		inode->i_blocks = 0;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 		inode->i_generation = prandom_u32();
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 644b17ec9e63..9d6d3da2caf2 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3140,13 +3140,13 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
 	}
 
 	if (!selinux_initialized(&selinux_state))
-		return (inode_owner_or_capable(inode) ? 0 : -EPERM);
+		return (inode_owner_or_capable(&init_user_ns, inode) ? 0 : -EPERM);
 
 	sbsec = inode->i_sb->s_security;
 	if (!(sbsec->flags & SBLABEL_MNT))
 		return -EOPNOTSUPP;
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EPERM;
 
 	ad.type = LSM_AUDIT_DATA_DENTRY;