Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs update from Miklos Szeredi:
 "First of all, this fixes a regression in overlayfs introduced by the
  dentry hash salting.  I've moved the patch fixing this to the front of
  the queue, so if (god forbid) something needs to be bisected in
  overlayfs this regression won't interfere with that.

  The biggest part is preparation for selinux support, done by Vivek
  Goyal.  Essentially this makes all operations on underlying
  filesystems be done with credentials of mounter.  This makes
  everything nicely consistent.

  There are also fixes for a number of known and recently discovered
  non-standard behavior (thanks to Eryu Guan for testing and improving
  the test suites)"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (23 commits)
  ovl: simplify empty checking
  qstr: constify instances in overlayfs
  ovl: clear nlink on rmdir
  ovl: disallow overlayfs as upperdir
  ovl: fix warning
  ovl: remove duplicated include from super.c
  ovl: append MAY_READ when diluting write checks
  ovl: dilute permission checks on lower only if not special file
  ovl: fix POSIX ACL setting
  ovl: share inode for hard link
  ovl: store real inode pointer in ->i_private
  ovl: permission: return ECHILD instead of ENOENT
  ovl: update atime on upper
  ovl: fix sgid on directory
  ovl: simplify permission checking
  ovl: do not require mounter to have MAY_WRITE on lower
  ovl: do operations on underlying file system in mounter's context
  ovl: modify ovl_permission() to do checks on two inodes
  ovl: define ->get_acl() for overlay inodes
  ovl: move some common code in a function
  ...

1 files changed, 144 insertions, 34 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5e254b3a8c56..4036132842b5 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -16,10 +16,10 @@
 #include <linux/slab.h>
 #include <linux/parser.h>
 #include <linux/module.h>
-#include <linux/pagemap.h>
 #include <linux/sched.h>
 #include <linux/statfs.h>
 #include <linux/seq_file.h>
+#include <linux/posix_acl_xattr.h>
 #include "overlayfs.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -145,18 +145,11 @@ struct dentry *ovl_dentry_real(struct dentry *dentry)
 	return realdentry;
 }
 
-struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
+static void ovl_inode_init(struct inode *inode, struct inode *realinode,
+			   bool is_upper)
 {
-	struct dentry *realdentry;
-
-	realdentry = ovl_upperdentry_dereference(oe);
-	if (realdentry) {
-		*is_upper = true;
-	} else {
-		realdentry = __ovl_dentry_lower(oe);
-		*is_upper = false;
-	}
-	return realdentry;
+	WRITE_ONCE(inode->i_private, (unsigned long) realinode |
+		   (is_upper ? OVL_ISUPPER_MASK : 0));
 }
 
 struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
@@ -178,13 +171,6 @@ struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 	return oe->cache;
 }
 
-bool ovl_is_default_permissions(struct inode *inode)
-{
-	struct ovl_fs *ofs = inode->i_sb->s_fs_info;
-
-	return ofs->config.default_permissions;
-}
-
 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
@@ -235,7 +221,6 @@ void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
 
 	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
 	WARN_ON(oe->__upperdentry);
-	BUG_ON(!upperdentry->d_inode);
 	/*
 	 * Make sure upperdentry is consistent before making it visible to
 	 * ovl_upperdentry_dereference().
@@ -244,6 +229,16 @@ void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
 	oe->__upperdentry = upperdentry;
 }
 
+void ovl_inode_update(struct inode *inode, struct inode *upperinode)
+{
+	WARN_ON(!upperinode);
+	WARN_ON(!inode_unhashed(inode));
+	WRITE_ONCE(inode->i_private,
+		   (unsigned long) upperinode | OVL_ISUPPER_MASK);
+	if (!S_ISDIR(upperinode->i_mode))
+		__insert_inode_hash(inode, (unsigned long) upperinode);
+}
+
 void ovl_dentry_version_inc(struct dentry *dentry)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
@@ -340,7 +335,7 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
 	/* Handle recursion */
 	return d_real(real, inode, open_flags);
 bug:
-	WARN(1, "ovl_d_real(%pd4, %s:%lu\n): real dentry not found\n", dentry,
+	WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
 	     inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
 	return dentry;
 }
@@ -412,7 +407,8 @@ static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
 static bool ovl_dentry_remote(struct dentry *dentry)
 {
 	return dentry->d_flags &
-		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
+		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
+		 DCACHE_OP_REAL);
 }
 
 static bool ovl_dentry_weird(struct dentry *dentry)
@@ -423,12 +419,16 @@ static bool ovl_dentry_weird(struct dentry *dentry)
 				  DCACHE_OP_COMPARE);
 }
 
-static inline struct dentry *ovl_lookup_real(struct dentry *dir,
-					     struct qstr *name)
+static inline struct dentry *ovl_lookup_real(struct super_block *ovl_sb,
+					     struct dentry *dir,
+					     const struct qstr *name)
 {
+	const struct cred *old_cred;
 	struct dentry *dentry;
 
-	dentry = lookup_hash(name, dir);
+	old_cred = ovl_override_creds(ovl_sb);
+	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
+	revert_creds(old_cred);
 
 	if (IS_ERR(dentry)) {
 		if (PTR_ERR(dentry) == -ENOENT)
@@ -481,7 +481,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 
 	upperdir = ovl_upperdentry_dereference(poe);
 	if (upperdir) {
-		this = ovl_lookup_real(upperdir, &dentry->d_name);
+		this = ovl_lookup_real(dentry->d_sb, upperdir, &dentry->d_name);
 		err = PTR_ERR(this);
 		if (IS_ERR(this))
 			goto out;
@@ -514,7 +514,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		bool opaque = false;
 		struct path lowerpath = poe->lowerstack[i];
 
-		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
+		this = ovl_lookup_real(dentry->d_sb,
+				       lowerpath.dentry, &dentry->d_name);
 		err = PTR_ERR(this);
 		if (IS_ERR(this)) {
 			/*
@@ -569,12 +570,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 
 	if (upperdentry || ctr) {
 		struct dentry *realdentry;
+		struct inode *realinode;
 
 		realdentry = upperdentry ? upperdentry : stack[0].dentry;
+		realinode = d_inode(realdentry);
 
 		err = -ENOMEM;
-		inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
-				      oe);
+		if (upperdentry && !d_is_dir(upperdentry)) {
+			inode = ovl_get_inode(dentry->d_sb, realinode);
+		} else {
+			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode);
+			if (inode)
+				ovl_inode_init(inode, realinode, !!upperdentry);
+		}
 		if (!inode)
 			goto out_free_oe;
 		ovl_copyattr(realdentry->d_inode, inode);
@@ -603,7 +611,7 @@ out:
 
 struct file *ovl_path_open(struct path *path, int flags)
 {
-	return dentry_open(path, flags, current_cred());
+	return dentry_open(path, flags | O_NOATIME, current_cred());
 }
 
 static void ovl_put_super(struct super_block *sb)
@@ -686,6 +694,7 @@ static const struct super_operations ovl_super_operations = {
 	.statfs		= ovl_statfs,
 	.show_options	= ovl_show_options,
 	.remount_fs	= ovl_remount,
+	.drop_inode	= generic_delete_inode,
 };
 
 enum {
@@ -958,11 +967,102 @@ static unsigned int ovl_split_lowerdirs(char *str)
 	return ctr;
 }
 
+static int ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
+				   struct dentry *dentry, struct inode *inode,
+				   const char *name, const void *value,
+				   size_t size, int flags)
+{
+	struct dentry *workdir = ovl_workdir(dentry);
+	struct inode *realinode = ovl_inode_real(inode, NULL);
+	struct posix_acl *acl = NULL;
+	int err;
+
+	/* Check that everything is OK before copy-up */
+	if (value) {
+		acl = posix_acl_from_xattr(&init_user_ns, value, size);
+		if (IS_ERR(acl))
+			return PTR_ERR(acl);
+	}
+	err = -EOPNOTSUPP;
+	if (!IS_POSIXACL(d_inode(workdir)))
+		goto out_acl_release;
+	if (!realinode->i_op->set_acl)
+		goto out_acl_release;
+	if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
+		err = acl ? -EACCES : 0;
+		goto out_acl_release;
+	}
+	err = -EPERM;
+	if (!inode_owner_or_capable(inode))
+		goto out_acl_release;
+
+	posix_acl_release(acl);
+
+	return ovl_setxattr(dentry, inode, handler->name, value, size, flags);
+
+out_acl_release:
+	posix_acl_release(acl);
+	return err;
+}
+
+static int ovl_other_xattr_set(const struct xattr_handler *handler,
+			       struct dentry *dentry, struct inode *inode,
+			       const char *name, const void *value,
+			       size_t size, int flags)
+{
+	return ovl_setxattr(dentry, inode, name, value, size, flags);
+}
+
+static int ovl_own_xattr_set(const struct xattr_handler *handler,
+			     struct dentry *dentry, struct inode *inode,
+			     const char *name, const void *value,
+			     size_t size, int flags)
+{
+	return -EPERM;
+}
+
+static const struct xattr_handler ovl_posix_acl_access_xattr_handler = {
+	.name = XATTR_NAME_POSIX_ACL_ACCESS,
+	.flags = ACL_TYPE_ACCESS,
+	.set = ovl_posix_acl_xattr_set,
+};
+
+static const struct xattr_handler ovl_posix_acl_default_xattr_handler = {
+	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
+	.flags = ACL_TYPE_DEFAULT,
+	.set = ovl_posix_acl_xattr_set,
+};
+
+static const struct xattr_handler ovl_own_xattr_handler = {
+	.prefix	= OVL_XATTR_PREFIX,
+	.set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_other_xattr_handler = {
+	.prefix	= "", /* catch all */
+	.set = ovl_other_xattr_set,
+};
+
+static const struct xattr_handler *ovl_xattr_handlers[] = {
+	&ovl_posix_acl_access_xattr_handler,
+	&ovl_posix_acl_default_xattr_handler,
+	&ovl_own_xattr_handler,
+	&ovl_other_xattr_handler,
+	NULL
+};
+
+static const struct xattr_handler *ovl_xattr_noacl_handlers[] = {
+	&ovl_own_xattr_handler,
+	&ovl_other_xattr_handler,
+	NULL,
+};
+
 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct path upperpath = { NULL, NULL };
 	struct path workpath = { NULL, NULL };
 	struct dentry *root_dentry;
+	struct inode *realinode;
 	struct ovl_entry *oe;
 	struct ovl_fs *ufs;
 	struct path *stack = NULL;
@@ -1069,6 +1169,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			pr_err("overlayfs: failed to clone upperpath\n");
 			goto out_put_lowerpath;
 		}
+		/* Don't inherit atime flags */
+		ufs->upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
+
+		sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
 
 		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
 		err = PTR_ERR(ufs->workdir);
@@ -1116,7 +1220,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		 * Make lower_mnt R/O.  That way fchmod/fchown on lower file
 		 * will fail instead of modifying lower fs.
 		 */
-		mnt->mnt_flags |= MNT_READONLY;
+		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
 
 		ufs->lower_mnt[ufs->numlower] = mnt;
 		ufs->numlower++;
@@ -1140,7 +1244,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	if (!oe)
 		goto out_put_cred;
 
-	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
+	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR));
 	if (!root_dentry)
 		goto out_free_oe;
 
@@ -1159,13 +1263,19 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 
 	root_dentry->d_fsdata = oe;
 
-	ovl_copyattr(ovl_dentry_real(root_dentry)->d_inode,
-		     root_dentry->d_inode);
+	realinode = d_inode(ovl_dentry_real(root_dentry));
+	ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);
+	ovl_copyattr(realinode, d_inode(root_dentry));
 
 	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
 	sb->s_op = &ovl_super_operations;
+	if (IS_ENABLED(CONFIG_FS_POSIX_ACL))
+		sb->s_xattr = ovl_xattr_handlers;
+	else
+		sb->s_xattr = ovl_xattr_noacl_handlers;
 	sb->s_root = root_dentry;
 	sb->s_fs_info = ufs;
+	sb->s_flags |= MS_POSIXACL;
 
 	return 0;