kernel: backport upstream overlayfs fixes

First two patches weren't marked for stable but are dependencies for
laters ones. The rest of patches was marked for stable but most likely
will be backported to 4.5+ only so we need to get them on our own.

An important fix is eea2fb4851e9d ("ovl: proper cleanup of workdir") as
it allows mounting overlayfs with dirty workdir, e.g. after power cut.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

7 files changed, 749 insertions, 0 deletions

diff --git a/target/linux/generic/patches-4.4/051-0001-ovl-rename-is_merge-to-is_lowest.patch b/target/linux/generic/patches-4.4/051-0001-ovl-rename-is_merge-to-is_lowest.patch
new file mode 100644
index 0000000..79140b9
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0001-ovl-rename-is_merge-to-is_lowest.patch
@@ -0,0 +1,72 @@
+From 56656e960b555cb98bc414382566dcb59aae99a2 Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszeredi@redhat.com>
+Date: Mon, 21 Mar 2016 17:31:46 +0100
+Subject: [PATCH] ovl: rename is_merge to is_lowest
+
+The 'is_merge' is an historical naming from when only a single lower layer
+could exist.  With the introduction of multiple lower layers the meaning of
+this flag was changed to mean only the "lowest layer" (while all lower
+layers were being merged).
+
+So now 'is_merge' is inaccurate and hence renaming to 'is_lowest'
+
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+---
+ fs/overlayfs/readdir.c | 16 ++++++++--------
+ 1 file changed, 8 insertions(+), 8 deletions(-)
+
+--- a/fs/overlayfs/readdir.c
++++ b/fs/overlayfs/readdir.c
+@@ -36,7 +36,7 @@ struct ovl_dir_cache {
+ 
+ struct ovl_readdir_data {
+ 	struct dir_context ctx;
+-	bool is_merge;
++	bool is_lowest;
+ 	struct rb_root root;
+ 	struct list_head *list;
+ 	struct list_head middle;
+@@ -139,9 +139,9 @@ static int ovl_cache_entry_add_rb(struct
+ 	return 0;
+ }
+ 
+-static int ovl_fill_lower(struct ovl_readdir_data *rdd,
+-			  const char *name, int namelen,
+-			  loff_t offset, u64 ino, unsigned int d_type)
++static int ovl_fill_lowest(struct ovl_readdir_data *rdd,
++			   const char *name, int namelen,
++			   loff_t offset, u64 ino, unsigned int d_type)
+ {
+ 	struct ovl_cache_entry *p;
+ 
+@@ -193,10 +193,10 @@ static int ovl_fill_merge(struct dir_con
+ 		container_of(ctx, struct ovl_readdir_data, ctx);
+ 
+ 	rdd->count++;
+-	if (!rdd->is_merge)
++	if (!rdd->is_lowest)
+ 		return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
+ 	else
+-		return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
++		return ovl_fill_lowest(rdd, name, namelen, offset, ino, d_type);
+ }
+ 
+ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
+@@ -289,7 +289,7 @@ static int ovl_dir_read_merged(struct de
+ 		.ctx.actor = ovl_fill_merge,
+ 		.list = list,
+ 		.root = RB_ROOT,
+-		.is_merge = false,
++		.is_lowest = false,
+ 	};
+ 	int idx, next;
+ 
+@@ -306,7 +306,7 @@ static int ovl_dir_read_merged(struct de
+ 			 * allows offsets to be reasonably constant
+ 			 */
+ 			list_add(&rdd.middle, rdd.list);
+-			rdd.is_merge = true;
++			rdd.is_lowest = true;
+ 			err = ovl_dir_read(&realpath, &rdd);
+ 			list_del(&rdd.middle);
+ 		}
diff --git a/target/linux/generic/patches-4.4/051-0002-ovl-override-creds-with-the-ones-from-the-superblock.patch b/target/linux/generic/patches-4.4/051-0002-ovl-override-creds-with-the-ones-from-the-superblock.patch
new file mode 100644
index 0000000..8a7d00a
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0002-ovl-override-creds-with-the-ones-from-the-superblock.patch
@@ -0,0 +1,336 @@
+From 3fe6e52f062643676eb4518d68cee3bc1272091b Mon Sep 17 00:00:00 2001
+From: Antonio Murdaca <amurdaca@redhat.com>
+Date: Thu, 7 Apr 2016 15:48:25 +0200
+Subject: [PATCH] ovl: override creds with the ones from the superblock mounter
+
+In user namespace the whiteout creation fails with -EPERM because the
+current process isn't capable(CAP_SYS_ADMIN) when setting xattr.
+
+A simple reproducer:
+
+$ mkdir upper lower work merged lower/dir
+$ sudo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged
+$ unshare -m -p -f -U -r bash
+
+Now as root in the user namespace:
+
+\# touch merged/dir/{1,2,3} # this will force a copy up of lower/dir
+\# rm -fR merged/*
+
+This ends up failing with -EPERM after the files in dir has been
+correctly deleted:
+
+unlinkat(4, "2", 0)                     = 0
+unlinkat(4, "1", 0)                     = 0
+unlinkat(4, "3", 0)                     = 0
+close(4)                                = 0
+unlinkat(AT_FDCWD, "merged/dir", AT_REMOVEDIR) = -1 EPERM (Operation not
+permitted)
+
+Interestingly, if you don't place files in merged/dir you can remove it,
+meaning if upper/dir does not exist, creating the char device file works
+properly in that same location.
+
+This patch uses ovl_sb_creator_cred() to get the cred struct from the
+superblock mounter and override the old cred with these new ones so that
+the whiteout creation is possible because overlay is wrong in assuming that
+the creds it will get with prepare_creds will be in the initial user
+namespace.  The old cap_raise game is removed in favor of just overriding
+the old cred struct.
+
+This patch also drops from ovl_copy_up_one() the following two lines:
+
+override_cred->fsuid = stat->uid;
+override_cred->fsgid = stat->gid;
+
+This is because the correct uid and gid are taken directly with the stat
+struct and correctly set with ovl_set_attr().
+
+Signed-off-by: Antonio Murdaca <runcom@redhat.com>
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+---
+ fs/overlayfs/copy_up.c   | 26 +------------------
+ fs/overlayfs/dir.c       | 67 ++++--------------------------------------------
+ fs/overlayfs/overlayfs.h |  1 +
+ fs/overlayfs/readdir.c   | 14 +++-------
+ fs/overlayfs/super.c     | 18 ++++++++++++-
+ 5 files changed, 27 insertions(+), 99 deletions(-)
+
+--- a/fs/overlayfs/copy_up.c
++++ b/fs/overlayfs/copy_up.c
+@@ -303,7 +303,6 @@ int ovl_copy_up_one(struct dentry *paren
+ 	struct dentry *upperdir;
+ 	struct dentry *upperdentry;
+ 	const struct cred *old_cred;
+-	struct cred *override_cred;
+ 	char *link = NULL;
+ 
+ 	if (WARN_ON(!workdir))
+@@ -322,28 +321,7 @@ int ovl_copy_up_one(struct dentry *paren
+ 			return PTR_ERR(link);
+ 	}
+ 
+-	err = -ENOMEM;
+-	override_cred = prepare_creds();
+-	if (!override_cred)
+-		goto out_free_link;
+-
+-	override_cred->fsuid = stat->uid;
+-	override_cred->fsgid = stat->gid;
+-	/*
+-	 * CAP_SYS_ADMIN for copying up extended attributes
+-	 * CAP_DAC_OVERRIDE for create
+-	 * CAP_FOWNER for chmod, timestamp update
+-	 * CAP_FSETID for chmod
+-	 * CAP_CHOWN for chown
+-	 * CAP_MKNOD for mknod
+-	 */
+-	cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+-	cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+-	cap_raise(override_cred->cap_effective, CAP_FOWNER);
+-	cap_raise(override_cred->cap_effective, CAP_FSETID);
+-	cap_raise(override_cred->cap_effective, CAP_CHOWN);
+-	cap_raise(override_cred->cap_effective, CAP_MKNOD);
+-	old_cred = override_creds(override_cred);
++	old_cred = ovl_override_creds(dentry->d_sb);
+ 
+ 	err = -EIO;
+ 	if (lock_rename(workdir, upperdir) != NULL) {
+@@ -366,9 +344,7 @@ int ovl_copy_up_one(struct dentry *paren
+ out_unlock:
+ 	unlock_rename(workdir, upperdir);
+ 	revert_creds(old_cred);
+-	put_cred(override_cred);
+ 
+-out_free_link:
+ 	if (link)
+ 		free_page((unsigned long) link);
+ 
+--- a/fs/overlayfs/dir.c
++++ b/fs/overlayfs/dir.c
+@@ -405,28 +405,13 @@ static int ovl_create_or_link(struct den
+ 		err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
+ 	} else {
+ 		const struct cred *old_cred;
+-		struct cred *override_cred;
+ 
+-		err = -ENOMEM;
+-		override_cred = prepare_creds();
+-		if (!override_cred)
+-			goto out_iput;
+-
+-		/*
+-		 * CAP_SYS_ADMIN for setting opaque xattr
+-		 * CAP_DAC_OVERRIDE for create in workdir, rename
+-		 * CAP_FOWNER for removing whiteout from sticky dir
+-		 */
+-		cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+-		cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+-		cap_raise(override_cred->cap_effective, CAP_FOWNER);
+-		old_cred = override_creds(override_cred);
++		old_cred = ovl_override_creds(dentry->d_sb);
+ 
+ 		err = ovl_create_over_whiteout(dentry, inode, &stat, link,
+ 					       hardlink);
+ 
+ 		revert_creds(old_cred);
+-		put_cred(override_cred);
+ 	}
+ 
+ 	if (!err)
+@@ -656,32 +641,11 @@ static int ovl_do_remove(struct dentry *
+ 	if (OVL_TYPE_PURE_UPPER(type)) {
+ 		err = ovl_remove_upper(dentry, is_dir);
+ 	} else {
+-		const struct cred *old_cred;
+-		struct cred *override_cred;
+-
+-		err = -ENOMEM;
+-		override_cred = prepare_creds();
+-		if (!override_cred)
+-			goto out_drop_write;
+-
+-		/*
+-		 * CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
+-		 * CAP_DAC_OVERRIDE for create in workdir, rename
+-		 * CAP_FOWNER for removing whiteout from sticky dir
+-		 * CAP_FSETID for chmod of opaque dir
+-		 * CAP_CHOWN for chown of opaque dir
+-		 */
+-		cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+-		cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+-		cap_raise(override_cred->cap_effective, CAP_FOWNER);
+-		cap_raise(override_cred->cap_effective, CAP_FSETID);
+-		cap_raise(override_cred->cap_effective, CAP_CHOWN);
+-		old_cred = override_creds(override_cred);
++		const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
+ 
+ 		err = ovl_remove_and_whiteout(dentry, is_dir);
+ 
+ 		revert_creds(old_cred);
+-		put_cred(override_cred);
+ 	}
+ out_drop_write:
+ 	ovl_drop_write(dentry);
+@@ -720,7 +684,6 @@ static int ovl_rename2(struct inode *old
+ 	bool new_is_dir = false;
+ 	struct dentry *opaquedir = NULL;
+ 	const struct cred *old_cred = NULL;
+-	struct cred *override_cred = NULL;
+ 
+ 	err = -EINVAL;
+ 	if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
+@@ -789,26 +752,8 @@ static int ovl_rename2(struct inode *old
+ 	old_opaque = !OVL_TYPE_PURE_UPPER(old_type);
+ 	new_opaque = !OVL_TYPE_PURE_UPPER(new_type);
+ 
+-	if (old_opaque || new_opaque) {
+-		err = -ENOMEM;
+-		override_cred = prepare_creds();
+-		if (!override_cred)
+-			goto out_drop_write;
+-
+-		/*
+-		 * CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
+-		 * CAP_DAC_OVERRIDE for create in workdir
+-		 * CAP_FOWNER for removing whiteout from sticky dir
+-		 * CAP_FSETID for chmod of opaque dir
+-		 * CAP_CHOWN for chown of opaque dir
+-		 */
+-		cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
+-		cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+-		cap_raise(override_cred->cap_effective, CAP_FOWNER);
+-		cap_raise(override_cred->cap_effective, CAP_FSETID);
+-		cap_raise(override_cred->cap_effective, CAP_CHOWN);
+-		old_cred = override_creds(override_cred);
+-	}
++	if (old_opaque || new_opaque)
++		old_cred = ovl_override_creds(old->d_sb);
+ 
+ 	if (overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir) {
+ 		opaquedir = ovl_check_empty_and_clear(new);
+@@ -939,10 +884,8 @@ out_dput_old:
+ out_unlock:
+ 	unlock_rename(new_upperdir, old_upperdir);
+ out_revert_creds:
+-	if (old_opaque || new_opaque) {
++	if (old_opaque || new_opaque)
+ 		revert_creds(old_cred);
+-		put_cred(override_cred);
+-	}
+ out_drop_write:
+ 	ovl_drop_write(old);
+ out:
+--- a/fs/overlayfs/overlayfs.h
++++ b/fs/overlayfs/overlayfs.h
+@@ -150,6 +150,7 @@ void ovl_drop_write(struct dentry *dentr
+ bool ovl_dentry_is_opaque(struct dentry *dentry);
+ void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
+ bool ovl_is_whiteout(struct dentry *dentry);
++const struct cred *ovl_override_creds(struct super_block *sb);
+ void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
+ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
+ 			  unsigned int flags);
+--- a/fs/overlayfs/readdir.c
++++ b/fs/overlayfs/readdir.c
+@@ -36,6 +36,7 @@ struct ovl_dir_cache {
+ 
+ struct ovl_readdir_data {
+ 	struct dir_context ctx;
++	struct dentry *dentry;
+ 	bool is_lowest;
+ 	struct rb_root root;
+ 	struct list_head *list;
+@@ -205,17 +206,8 @@ static int ovl_check_whiteouts(struct de
+ 	struct ovl_cache_entry *p;
+ 	struct dentry *dentry;
+ 	const struct cred *old_cred;
+-	struct cred *override_cred;
+-
+-	override_cred = prepare_creds();
+-	if (!override_cred)
+-		return -ENOMEM;
+ 
+-	/*
+-	 * CAP_DAC_OVERRIDE for lookup
+-	 */
+-	cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+-	old_cred = override_creds(override_cred);
++	old_cred = ovl_override_creds(rdd->dentry->d_sb);
+ 
+ 	err = mutex_lock_killable(&dir->d_inode->i_mutex);
+ 	if (!err) {
+@@ -231,7 +223,6 @@ static int ovl_check_whiteouts(struct de
+ 		mutex_unlock(&dir->d_inode->i_mutex);
+ 	}
+ 	revert_creds(old_cred);
+-	put_cred(override_cred);
+ 
+ 	return err;
+ }
+@@ -287,6 +278,7 @@ static int ovl_dir_read_merged(struct de
+ 	struct path realpath;
+ 	struct ovl_readdir_data rdd = {
+ 		.ctx.actor = ovl_fill_merge,
++		.dentry = dentry,
+ 		.list = list,
+ 		.root = RB_ROOT,
+ 		.is_lowest = false,
+--- a/fs/overlayfs/super.c
++++ b/fs/overlayfs/super.c
+@@ -42,6 +42,8 @@ struct ovl_fs {
+ 	long lower_namelen;
+ 	/* pathnames of lower and upper dirs, for show_options */
+ 	struct ovl_config config;
++	/* creds of process who forced instantiation of super block */
++	const struct cred *creator_cred;
+ };
+ 
+ struct ovl_dir_cache;
+@@ -246,6 +248,13 @@ bool ovl_is_whiteout(struct dentry *dent
+ 	return inode && IS_WHITEOUT(inode);
+ }
+ 
++const struct cred *ovl_override_creds(struct super_block *sb)
++{
++	struct ovl_fs *ofs = sb->s_fs_info;
++
++	return override_creds(ofs->creator_cred);
++}
++
+ static bool ovl_is_opaquedir(struct dentry *dentry)
+ {
+ 	int res;
+@@ -587,6 +596,7 @@ static void ovl_put_super(struct super_b
+ 	kfree(ufs->config.lowerdir);
+ 	kfree(ufs->config.upperdir);
+ 	kfree(ufs->config.workdir);
++	put_cred(ufs->creator_cred);
+ 	kfree(ufs);
+ }
+ 
+@@ -1068,10 +1078,14 @@ static int ovl_fill_super(struct super_b
+ 	else
+ 		sb->s_d_op = &ovl_dentry_operations;
+ 
++	ufs->creator_cred = prepare_creds();
++	if (!ufs->creator_cred)
++		goto out_put_lower_mnt;
++
+ 	err = -ENOMEM;
+ 	oe = ovl_alloc_entry(numlower);
+ 	if (!oe)
+-		goto out_put_lower_mnt;
++		goto out_put_cred;
+ 
+ 	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
+ 	if (!root_dentry)
+@@ -1104,6 +1118,8 @@ static int ovl_fill_super(struct super_b
+ 
+ out_free_oe:
+ 	kfree(oe);
++out_put_cred:
++	put_cred(ufs->creator_cred);
+ out_put_lower_mnt:
+ 	for (i = 0; i < ufs->numlower; i++)
+ 		mntput(ufs->lower_mnt[i]);
diff --git a/target/linux/generic/patches-4.4/051-0003-ovl-don-t-copy-up-opaqueness.patch b/target/linux/generic/patches-4.4/051-0003-ovl-don-t-copy-up-opaqueness.patch
new file mode 100644
index 0000000..da9e380
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0003-ovl-don-t-copy-up-opaqueness.patch
@@ -0,0 +1,73 @@
+From 0956254a2d5b9e2141385514553aeef694dfe3b5 Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszeredi@redhat.com>
+Date: Mon, 8 Aug 2016 15:08:49 +0200
+Subject: [PATCH] ovl: don't copy up opaqueness
+
+When a copy up of a directory occurs which has the opaque xattr set, the
+xattr remains in the upper directory. The immediate behavior with overlayfs
+is that the upper directory is not treated as opaque, however after a
+remount the opaque flag is used and upper directory is treated as opaque.
+This causes files created in the lower layer to be hidden when using
+multiple lower directories.
+
+Fix by not copying up the opaque flag.
+
+To reproduce:
+
+ ----8<---------8<---------8<---------8<---------8<---------8<----
+mkdir -p l/d/s u v w mnt
+mount -t overlay overlay -olowerdir=l,upperdir=u,workdir=w mnt
+rm -rf mnt/d/
+mkdir -p mnt/d/n
+umount mnt
+mount -t overlay overlay -olowerdir=u:l,upperdir=v,workdir=w mnt
+touch mnt/d/foo
+umount mnt
+mount -t overlay overlay -olowerdir=u:l,upperdir=v,workdir=w mnt
+ls mnt/d
+ ----8<---------8<---------8<---------8<---------8<---------8<----
+
+output should be:  "foo  n"
+
+Reported-by: Derek McGowan <dmcg@drizz.net>
+Link: https://bugzilla.kernel.org/show_bug.cgi?id=151291
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+Cc: <stable@vger.kernel.org>
+---
+ fs/overlayfs/copy_up.c   | 2 ++
+ fs/overlayfs/inode.c     | 2 +-
+ fs/overlayfs/overlayfs.h | 1 +
+ 3 files changed, 4 insertions(+), 1 deletion(-)
+
+--- a/fs/overlayfs/copy_up.c
++++ b/fs/overlayfs/copy_up.c
+@@ -48,6 +48,8 @@ int ovl_copy_xattr(struct dentry *old, s
+ 	}
+ 
+ 	for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
++		if (ovl_is_private_xattr(name))
++			continue;
+ retry:
+ 		size = vfs_getxattr(old, name, value, value_size);
+ 		if (size == -ERANGE)
+--- a/fs/overlayfs/inode.c
++++ b/fs/overlayfs/inode.c
+@@ -219,7 +219,7 @@ static int ovl_readlink(struct dentry *d
+ }
+ 
+ 
+-static bool ovl_is_private_xattr(const char *name)
++bool ovl_is_private_xattr(const char *name)
+ {
+ 	return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
+ }
+--- a/fs/overlayfs/overlayfs.h
++++ b/fs/overlayfs/overlayfs.h
+@@ -175,6 +175,7 @@ ssize_t ovl_getxattr(struct dentry *dent
+ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
+ int ovl_removexattr(struct dentry *dentry, const char *name);
+ struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags);
++bool ovl_is_private_xattr(const char *name);
+ 
+ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
+ 			    struct ovl_entry *oe);
diff --git a/target/linux/generic/patches-4.4/051-0004-ovl-remove-posix_acl_default-from-workdir.patch b/target/linux/generic/patches-4.4/051-0004-ovl-remove-posix_acl_default-from-workdir.patch
new file mode 100644
index 0000000..1785c9a
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0004-ovl-remove-posix_acl_default-from-workdir.patch
@@ -0,0 +1,49 @@
+From c11b9fdd6a612f376a5e886505f1c54c16d8c380 Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszeredi@redhat.com>
+Date: Thu, 1 Sep 2016 11:11:59 +0200
+Subject: [PATCH] ovl: remove posix_acl_default from workdir
+
+Clear out posix acl xattrs on workdir and also reset the mode after
+creation so that an inherited sgid bit is cleared.
+
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+Cc: <stable@vger.kernel.org>
+---
+ fs/overlayfs/super.c | 19 +++++++++++++++++++
+ 1 file changed, 19 insertions(+)
+
+--- a/fs/overlayfs/super.c
++++ b/fs/overlayfs/super.c
+@@ -773,6 +773,10 @@ retry:
+ 		struct kstat stat = {
+ 			.mode = S_IFDIR | 0,
+ 		};
++		struct iattr attr = {
++			.ia_valid = ATTR_MODE,
++			.ia_mode = stat.mode,
++		};
+ 
+ 		if (work->d_inode) {
+ 			err = -EEXIST;
+@@ -788,6 +792,21 @@ retry:
+ 		err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
+ 		if (err)
+ 			goto out_dput;
++
++		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
++		if (err && err != -ENODATA)
++			goto out_dput;
++
++		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
++		if (err && err != -ENODATA)
++			goto out_dput;
++
++		/* Clear any inherited mode bits */
++		mutex_lock(&work->d_inode->i_mutex);
++		err = notify_change(work, &attr, NULL);
++		mutex_unlock(&work->d_inode->i_mutex);
++		if (err)
++			goto out_dput;
+ 	}
+ out_unlock:
+ 	mutex_unlock(&dir->i_mutex);
diff --git a/target/linux/generic/patches-4.4/051-0005-ovl-proper-cleanup-of-workdir.patch b/target/linux/generic/patches-4.4/051-0005-ovl-proper-cleanup-of-workdir.patch
new file mode 100644
index 0000000..eb095b7
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0005-ovl-proper-cleanup-of-workdir.patch
@@ -0,0 +1,131 @@
+From eea2fb4851e9dcbab6b991aaf47e2e024f1f55a0 Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszeredi@redhat.com>
+Date: Thu, 1 Sep 2016 11:11:59 +0200
+Subject: [PATCH] ovl: proper cleanup of workdir
+
+When mounting overlayfs it needs a clean "work" directory under the
+supplied workdir.
+
+Previously the mount code removed this directory if it already existed and
+created a new one.  If the removal failed (e.g. directory was not empty)
+then it fell back to a read-only mount not using the workdir.
+
+While this has never been reported, it is possible to get a non-empty
+"work" dir from a previous mount of overlayfs in case of crash in the
+middle of an operation using the work directory.
+
+In this case the left over state should be discarded and the overlay
+filesystem will be consistent, guaranteed by the atomicity of operations on
+moving to/from the workdir to the upper layer.
+
+This patch implements cleaning out any files left in workdir.  It is
+implemented using real recursion for simplicity, but the depth is limited
+to 2, because the worst case is that of a directory containing whiteouts
+under "work".
+
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+Cc: <stable@vger.kernel.org>
+---
+ fs/overlayfs/overlayfs.h |  2 ++
+ fs/overlayfs/readdir.c   | 63 +++++++++++++++++++++++++++++++++++++++++++++++-
+ fs/overlayfs/super.c     |  2 +-
+ 3 files changed, 65 insertions(+), 2 deletions(-)
+
+--- a/fs/overlayfs/overlayfs.h
++++ b/fs/overlayfs/overlayfs.h
+@@ -164,6 +164,8 @@ extern const struct file_operations ovl_
+ int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list);
+ void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
+ void ovl_cache_free(struct list_head *list);
++void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
++			 struct dentry *dentry, int level);
+ 
+ /* inode.c */
+ int ovl_setattr(struct dentry *dentry, struct iattr *attr);
+--- a/fs/overlayfs/readdir.c
++++ b/fs/overlayfs/readdir.c
+@@ -247,7 +247,7 @@ static inline int ovl_dir_read(struct pa
+ 			err = rdd->err;
+ 	} while (!err && rdd->count);
+ 
+-	if (!err && rdd->first_maybe_whiteout)
++	if (!err && rdd->first_maybe_whiteout && rdd->dentry)
+ 		err = ovl_check_whiteouts(realpath->dentry, rdd);
+ 
+ 	fput(realfile);
+@@ -569,3 +569,64 @@ void ovl_cleanup_whiteouts(struct dentry
+ 	}
+ 	mutex_unlock(&upper->d_inode->i_mutex);
+ }
++
++static void ovl_workdir_cleanup_recurse(struct path *path, int level)
++{
++	int err;
++	struct inode *dir = path->dentry->d_inode;
++	LIST_HEAD(list);
++	struct ovl_cache_entry *p;
++	struct ovl_readdir_data rdd = {
++		.ctx.actor = ovl_fill_merge,
++		.dentry = NULL,
++		.list = &list,
++		.root = RB_ROOT,
++		.is_lowest = false,
++	};
++
++	err = ovl_dir_read(path, &rdd);
++	if (err)
++		goto out;
++
++	mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
++	list_for_each_entry(p, &list, l_node) {
++		struct dentry *dentry;
++
++		if (p->name[0] == '.') {
++			if (p->len == 1)
++				continue;
++			if (p->len == 2 && p->name[1] == '.')
++				continue;
++		}
++		dentry = lookup_one_len(p->name, path->dentry, p->len);
++		if (IS_ERR(dentry))
++			continue;
++		if (dentry->d_inode)
++			ovl_workdir_cleanup(dir, path->mnt, dentry, level);
++		dput(dentry);
++	}
++	mutex_unlock(&dir->i_mutex);
++out:
++	ovl_cache_free(&list);
++}
++
++void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
++			 struct dentry *dentry, int level)
++{
++	int err;
++
++	if (!d_is_dir(dentry) || level > 1) {
++		ovl_cleanup(dir, dentry);
++		return;
++	}
++
++	err = ovl_do_rmdir(dir, dentry);
++	if (err) {
++		struct path path = { .mnt = mnt, .dentry = dentry };
++
++		mutex_unlock(&dir->i_mutex);
++		ovl_workdir_cleanup_recurse(&path, level + 1);
++		mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
++		ovl_cleanup(dir, dentry);
++	}
++}
+--- a/fs/overlayfs/super.c
++++ b/fs/overlayfs/super.c
+@@ -784,7 +784,7 @@ retry:
+ 				goto out_dput;
+ 
+ 			retried = true;
+-			ovl_cleanup(dir, work);
++			ovl_workdir_cleanup(dir, mnt, work, 0);
+ 			dput(work);
+ 			goto retry;
+ 		}
diff --git a/target/linux/generic/patches-4.4/051-0006-ovl-listxattr-use-strnlen.patch b/target/linux/generic/patches-4.4/051-0006-ovl-listxattr-use-strnlen.patch
new file mode 100644
index 0000000..82ad20d
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0006-ovl-listxattr-use-strnlen.patch
@@ -0,0 +1,53 @@
+From 7cb35119d067191ce9ebc380a599db0b03cbd9d9 Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszeredi@redhat.com>
+Date: Thu, 1 Sep 2016 11:12:00 +0200
+Subject: [PATCH] ovl: listxattr: use strnlen()
+
+Be defensive about what underlying fs provides us in the returned xattr
+list buffer.  If it's not properly null terminated, bail out with a warning
+insead of BUG.
+
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+Cc: <stable@vger.kernel.org>
+---
+ fs/overlayfs/inode.c | 17 ++++++++++-------
+ 1 file changed, 10 insertions(+), 7 deletions(-)
+
+--- a/fs/overlayfs/inode.c
++++ b/fs/overlayfs/inode.c
+@@ -277,7 +277,8 @@ ssize_t ovl_listxattr(struct dentry *den
+ 	struct path realpath;
+ 	enum ovl_path_type type = ovl_path_real(dentry, &realpath);
+ 	ssize_t res;
+-	int off;
++	size_t len;
++	char *s;
+ 
+ 	res = vfs_listxattr(realpath.dentry, list, size);
+ 	if (res <= 0 || size == 0)
+@@ -287,17 +288,19 @@ ssize_t ovl_listxattr(struct dentry *den
+ 		return res;
+ 
+ 	/* filter out private xattrs */
+-	for (off = 0; off < res;) {
+-		char *s = list + off;
+-		size_t slen = strlen(s) + 1;
++	for (s = list, len = res; len;) {
++		size_t slen = strnlen(s, len) + 1;
+ 
+-		BUG_ON(off + slen > res);
++		/* underlying fs providing us with an broken xattr list? */
++		if (WARN_ON(slen > len))
++			return -EIO;
+ 
++		len -= slen;
+ 		if (ovl_is_private_xattr(s)) {
+ 			res -= slen;
+-			memmove(s, s + slen, res - off);
++			memmove(s, s + slen, len);
+ 		} else {
+-			off += slen;
++			s += slen;
+ 		}
+ 	}
+ 
diff --git a/target/linux/generic/patches-4.4/051-0007-ovl-fix-workdir-creation.patch b/target/linux/generic/patches-4.4/051-0007-ovl-fix-workdir-creation.patch
new file mode 100644
index 0000000..1f50170
--- /dev/null
+++ b/target/linux/generic/patches-4.4/051-0007-ovl-fix-workdir-creation.patch
@@ -0,0 +1,35 @@
+From e1ff3dd1ae52cef5b5373c8cc4ad949c2c25a71c Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszeredi@redhat.com>
+Date: Mon, 5 Sep 2016 13:55:20 +0200
+Subject: [PATCH] ovl: fix workdir creation
+
+Workdir creation fails in latest kernel.
+
+Fix by allowing EOPNOTSUPP as a valid return value from
+vfs_removexattr(XATTR_NAME_POSIX_ACL_*).  Upper filesystem may not support
+ACL and still be perfectly able to support overlayfs.
+
+Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
+Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
+Fixes: c11b9fdd6a61 ("ovl: remove posix_acl_default from workdir")
+Cc: <stable@vger.kernel.org>
+---
+ fs/overlayfs/super.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/fs/overlayfs/super.c
++++ b/fs/overlayfs/super.c
+@@ -794,11 +794,11 @@ retry:
+ 			goto out_dput;
+ 
+ 		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
+-		if (err && err != -ENODATA)
++		if (err && err != -ENODATA && err != -EOPNOTSUPP)
+ 			goto out_dput;
+ 
+ 		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
+-		if (err && err != -ENODATA)
++		if (err && err != -ENODATA && err != -EOPNOTSUPP)
+ 			goto out_dput;
+ 
+ 		/* Clear any inherited mode bits */