1 files changed, 157 insertions, 44 deletions

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index cfb3420b7df0..57adf911735f 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -14,6 +14,8 @@
 #include <linux/exportfs.h>
 #include "overlayfs.h"
 
+#include "../internal.h"	/* for vfs_path_lookup */
+
 struct ovl_lookup_data {
 	struct super_block *sb;
 	struct vfsmount *mnt;
@@ -24,6 +26,8 @@ struct ovl_lookup_data {
 	bool last;
 	char *redirect;
 	bool metacopy;
+	/* Referring to last redirect xattr */
+	bool absolute_redirect;
 };
 
 static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d,
@@ -33,11 +37,13 @@ static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d
 	char *buf;
 	struct ovl_fs *ofs = OVL_FS(d->sb);
 
+	d->absolute_redirect = false;
 	buf = ovl_get_redirect_xattr(ofs, path, prelen + strlen(post));
 	if (IS_ERR_OR_NULL(buf))
 		return PTR_ERR(buf);
 
 	if (buf[0] == '/') {
+		d->absolute_redirect = true;
 		/*
 		 * One of the ancestor path elements in an absolute path
 		 * lookup in ovl_lookup_layer() could have been opaque and
@@ -349,6 +355,61 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 	return 0;
 }
 
+static int ovl_lookup_data_layer(struct dentry *dentry, const char *redirect,
+				 const struct ovl_layer *layer,
+				 struct path *datapath)
+{
+	int err;
+
+	err = vfs_path_lookup(layer->mnt->mnt_root, layer->mnt, redirect,
+			LOOKUP_BENEATH | LOOKUP_NO_SYMLINKS | LOOKUP_NO_XDEV,
+			datapath);
+	pr_debug("lookup lowerdata (%pd2, redirect=\"%s\", layer=%d, err=%i)\n",
+		 dentry, redirect, layer->idx, err);
+
+	if (err)
+		return err;
+
+	err = -EREMOTE;
+	if (ovl_dentry_weird(datapath->dentry))
+		goto out_path_put;
+
+	err = -ENOENT;
+	/* Only regular file is acceptable as lower data */
+	if (!d_is_reg(datapath->dentry))
+		goto out_path_put;
+
+	return 0;
+
+out_path_put:
+	path_put(datapath);
+
+	return err;
+}
+
+/* Lookup in data-only layers by absolute redirect to layer root */
+static int ovl_lookup_data_layers(struct dentry *dentry, const char *redirect,
+				  struct ovl_path *lowerdata)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	const struct ovl_layer *layer;
+	struct path datapath;
+	int err = -ENOENT;
+	int i;
+
+	layer = &ofs->layers[ofs->numlayer - ofs->numdatalayer];
+	for (i = 0; i < ofs->numdatalayer; i++, layer++) {
+		err = ovl_lookup_data_layer(dentry, redirect, layer, &datapath);
+		if (!err) {
+			mntput(datapath.mnt);
+			lowerdata->dentry = datapath.dentry;
+			lowerdata->layer = layer;
+			return 0;
+		}
+	}
+
+	return err;
+}
 
 int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
 			struct dentry *upperdentry, struct ovl_path **stackp)
@@ -356,7 +417,7 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
 	struct dentry *origin = NULL;
 	int i;
 
-	for (i = 1; i < ofs->numlayer; i++) {
+	for (i = 1; i <= ovl_numlowerlayer(ofs); i++) {
 		/*
 		 * If lower fs uuid is not unique among lower fs we cannot match
 		 * fh->uuid to layer.
@@ -790,20 +851,21 @@ fail:
  */
 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
 {
-	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_entry *oe = OVL_E(dentry);
+	struct ovl_path *lowerstack = ovl_lowerstack(oe);
 
 	BUG_ON(idx < 0);
 	if (idx == 0) {
 		ovl_path_upper(dentry, path);
 		if (path->dentry)
-			return oe->numlower ? 1 : -1;
+			return ovl_numlower(oe) ? 1 : -1;
 		idx++;
 	}
-	BUG_ON(idx > oe->numlower);
-	path->dentry = oe->lowerstack[idx - 1].dentry;
-	path->mnt = oe->lowerstack[idx - 1].layer->mnt;
+	BUG_ON(idx > ovl_numlower(oe));
+	path->dentry = lowerstack[idx - 1].dentry;
+	path->mnt = lowerstack[idx - 1].layer->mnt;
 
-	return (idx < oe->numlower) ? idx + 1 : -1;
+	return (idx < ovl_numlower(oe)) ? idx + 1 : -1;
 }
 
 /* Fix missing 'origin' xattr */
@@ -827,14 +889,60 @@ static int ovl_fix_origin(struct ovl_fs *ofs, struct dentry *dentry,
 	return err;
 }
 
+/* Lazy lookup of lowerdata */
+int ovl_maybe_lookup_lowerdata(struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	const char *redirect = ovl_lowerdata_redirect(inode);
+	struct ovl_path datapath = {};
+	const struct cred *old_cred;
+	int err;
+
+	if (!redirect || ovl_dentry_lowerdata(dentry))
+		return 0;
+
+	if (redirect[0] != '/')
+		return -EIO;
+
+	err = ovl_inode_lock_interruptible(inode);
+	if (err)
+		return err;
+
+	err = 0;
+	/* Someone got here before us? */
+	if (ovl_dentry_lowerdata(dentry))
+		goto out;
+
+	old_cred = ovl_override_creds(dentry->d_sb);
+	err = ovl_lookup_data_layers(dentry, redirect, &datapath);
+	revert_creds(old_cred);
+	if (err)
+		goto out_err;
+
+	err = ovl_dentry_set_lowerdata(dentry, &datapath);
+	if (err)
+		goto out_err;
+
+out:
+	ovl_inode_unlock(inode);
+	dput(datapath.dentry);
+
+	return err;
+
+out_err:
+	pr_warn_ratelimited("lazy lowerdata lookup failed (%pd2, err=%i)\n",
+			    dentry, err);
+	goto out;
+}
+
 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			  unsigned int flags)
 {
-	struct ovl_entry *oe;
+	struct ovl_entry *oe = NULL;
 	const struct cred *old_cred;
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
-	struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
+	struct ovl_entry *poe = OVL_E(dentry->d_parent);
+	struct ovl_entry *roe = OVL_E(dentry->d_sb->s_root);
 	struct ovl_path *stack = NULL, *origin_path = NULL;
 	struct dentry *upperdir, *upperdentry = NULL;
 	struct dentry *origin = NULL;
@@ -853,7 +961,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		.is_dir = false,
 		.opaque = false,
 		.stop = false,
-		.last = ofs->config.redirect_follow ? false : !poe->numlower,
+		.last = ovl_redirect_follow(ofs) ? false : !ovl_numlower(poe),
 		.redirect = NULL,
 		.metacopy = false,
 	};
@@ -904,21 +1012,20 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		upperopaque = d.opaque;
 	}
 
-	if (!d.stop && poe->numlower) {
+	if (!d.stop && ovl_numlower(poe)) {
 		err = -ENOMEM;
-		stack = kcalloc(ofs->numlayer - 1, sizeof(struct ovl_path),
-				GFP_KERNEL);
+		stack = ovl_stack_alloc(ofs->numlayer - 1);
 		if (!stack)
 			goto out_put_upper;
 	}
 
-	for (i = 0; !d.stop && i < poe->numlower; i++) {
-		struct ovl_path lower = poe->lowerstack[i];
+	for (i = 0; !d.stop && i < ovl_numlower(poe); i++) {
+		struct ovl_path lower = ovl_lowerstack(poe)[i];
 
-		if (!ofs->config.redirect_follow)
-			d.last = i == poe->numlower - 1;
-		else
-			d.last = lower.layer->idx == roe->numlower;
+		if (!ovl_redirect_follow(ofs))
+			d.last = i == ovl_numlower(poe) - 1;
+		else if (d.is_dir || !ofs->numdatalayer)
+			d.last = lower.layer->idx == ovl_numlower(roe);
 
 		d.mnt = lower.layer->mnt;
 		err = ovl_lookup_layer(lower.dentry, &d, &this, false);
@@ -995,7 +1102,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		 * this attack vector when not necessary.
 		 */
 		err = -EPERM;
-		if (d.redirect && !ofs->config.redirect_follow) {
+		if (d.redirect && !ovl_redirect_follow(ofs)) {
 			pr_warn_ratelimited("refusing to follow redirect for (%pd2)\n",
 					    dentry);
 			goto out_put;
@@ -1011,6 +1118,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		}
 	}
 
+	/* Defer lookup of lowerdata in data-only layers to first access */
+	if (d.metacopy && ctr && ofs->numdatalayer && d.absolute_redirect) {
+		d.metacopy = false;
+		ctr++;
+	}
+
 	/*
 	 * For regular non-metacopy upper dentries, there is no lower
 	 * path based lookup, hence ctr will be zero. If a dentry is found
@@ -1067,13 +1180,14 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		}
 	}
 
-	oe = ovl_alloc_entry(ctr);
-	err = -ENOMEM;
-	if (!oe)
-		goto out_put;
+	if (ctr) {
+		oe = ovl_alloc_entry(ctr);
+		err = -ENOMEM;
+		if (!oe)
+			goto out_put;
 
-	memcpy(oe->lowerstack, stack, sizeof(struct ovl_path) * ctr);
-	dentry->d_fsdata = oe;
+		ovl_stack_cpy(ovl_lowerstack(oe), stack, ctr);
+	}
 
 	if (upperopaque)
 		ovl_dentry_set_opaque(dentry);
@@ -1106,14 +1220,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	if (upperdentry || ctr) {
 		struct ovl_inode_params oip = {
 			.upperdentry = upperdentry,
-			.lowerpath = stack,
+			.oe = oe,
 			.index = index,
-			.numlower = ctr,
 			.redirect = upperredirect,
-			.lowerdata = (ctr > 1 && !d.is_dir) ?
-				      stack[ctr - 1].dentry : NULL,
 		};
 
+		/* Store lowerdata redirect for lazy lookup */
+		if (ctr > 1 && !d.is_dir && !stack[ctr - 1].dentry) {
+			oip.lowerdata_redirect = d.redirect;
+			d.redirect = NULL;
+		}
 		inode = ovl_get_inode(dentry->d_sb, &oip);
 		err = PTR_ERR(inode);
 		if (IS_ERR(inode))
@@ -1122,8 +1238,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			ovl_set_flag(OVL_UPPERDATA, inode);
 	}
 
-	ovl_dentry_update_reval(dentry, upperdentry,
-			DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
+	ovl_dentry_init_reval(dentry, upperdentry, OVL_I_E(inode));
 
 	revert_creds(old_cred);
 	if (origin_path) {
@@ -1131,18 +1246,15 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		kfree(origin_path);
 	}
 	dput(index);
-	kfree(stack);
+	ovl_stack_free(stack, ctr);
 	kfree(d.redirect);
 	return d_splice_alias(inode, dentry);
 
 out_free_oe:
-	dentry->d_fsdata = NULL;
-	kfree(oe);
+	ovl_free_entry(oe);
 out_put:
 	dput(index);
-	for (i = 0; i < ctr; i++)
-		dput(stack[i].dentry);
-	kfree(stack);
+	ovl_stack_free(stack, ctr);
 out_put_upper:
 	if (origin_path) {
 		dput(origin_path->dentry);
@@ -1158,7 +1270,7 @@ out:
 
 bool ovl_lower_positive(struct dentry *dentry)
 {
-	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+	struct ovl_entry *poe = OVL_E(dentry->d_parent);
 	const struct qstr *name = &dentry->d_name;
 	const struct cred *old_cred;
 	unsigned int i;
@@ -1178,12 +1290,13 @@ bool ovl_lower_positive(struct dentry *dentry)
 
 	old_cred = ovl_override_creds(dentry->d_sb);
 	/* Positive upper -> have to look up lower to see whether it exists */
-	for (i = 0; !done && !positive && i < poe->numlower; i++) {
+	for (i = 0; !done && !positive && i < ovl_numlower(poe); i++) {
 		struct dentry *this;
-		struct dentry *lowerdir = poe->lowerstack[i].dentry;
+		struct ovl_path *parentpath = &ovl_lowerstack(poe)[i];
 
-		this = lookup_one_positive_unlocked(mnt_idmap(poe->lowerstack[i].layer->mnt),
-						   name->name, lowerdir, name->len);
+		this = lookup_one_positive_unlocked(
+				mnt_idmap(parentpath->layer->mnt),
+				name->name, parentpath->dentry, name->len);
 		if (IS_ERR(this)) {
 			switch (PTR_ERR(this)) {
 			case -ENOENT: