Lookup in data-only layers only for a lower metacopy with an absolute
redirect xattr.
The metacopy xattr is not checked on files found in the data-only layers
and redirect xattr are not followed in the data-only layers.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/namei.c | 77 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 75 insertions(+), 2 deletions(-)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index ff82155b4f7e..82e103e2308b 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)
@@ -907,7 +968,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
if (!d.stop && ovl_numlower(poe)) {
err = -ENOMEM;
- stack = ovl_stack_alloc(ovl_numlowerlayer(ofs));
+ /* May need to reserve space in lowerstack for lowerdata */
+ stack = ovl_stack_alloc(ovl_numlowerlayer(ofs) +
+ (!d.is_dir && !!ofs->numdatalayer));
if (!stack)
goto out_put_upper;
}
@@ -917,7 +980,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
if (!ofs->config.redirect_follow)
d.last = i == ovl_numlower(poe) - 1;
- else
+ else if (d.is_dir || !ofs->numdatalayer)
d.last = lower.layer->idx == ovl_numlower(roe);
d.mnt = lower.layer->mnt;
@@ -1011,6 +1074,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
}
}
+ /* Lookup absolute redirect from lower metacopy in data-only layers */
+ if (d.metacopy && ctr && ofs->numdatalayer && d.absolute_redirect) {
+ err = ovl_lookup_data_layers(dentry, d.redirect,
+ &stack[ctr]);
+ if (!err) {
+ 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
--
2.34.1
