diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index f213297d187e8d602f890dde83202b8e9471fbaa..9ad48d9202a99a6c63ccb07b9b31476f5ee524af 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -10,6 +10,7 @@
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/xattr.h>
+#include <linux/ratelimit.h>
#include "overlayfs.h"
#include "ovl_entry.h"
@@ -19,8 +20,66 @@ struct ovl_lookup_data {
bool opaque;
bool stop;
bool last;
+ char *redirect;
};
+static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
+ size_t prelen, const char *post)
+{
+ int res;
+ char *s, *next, *buf = NULL;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
+ if (res < 0) {
+ if (res == -ENODATA || res == -EOPNOTSUPP)
+ return 0;
+ goto fail;
+ }
+ buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY);
+ if (!buf)
+ return -ENOMEM;
+
+ if (res == 0)
+ goto invalid;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
+ if (res < 0)
+ goto fail;
+ if (res == 0)
+ goto invalid;
+ if (buf[0] == '/') {
+ for (s = buf; *s++ == '/'; s = next) {
+ next = strchrnul(s, '/');
+ if (s == next)
+ goto invalid;
+ }
+ } else {
+ if (strchr(buf, '/') != NULL)
+ goto invalid;
+
+ memmove(buf + prelen, buf, res);
+ memcpy(buf, d->name.name, prelen);
+ }
+
+ strcat(buf, post);
+ kfree(d->redirect);
+ d->redirect = buf;
+ d->name.name = d->redirect;
+ d->name.len = strlen(d->redirect);
+
+ return 0;
+
+err_free:
+ kfree(buf);
+ return 0;
+fail:
+ pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
+ goto err_free;
+invalid:
+ pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
+ goto err_free;
+}
+
static bool ovl_is_opaquedir(struct dentry *dentry)
{
int res;
@@ -38,6 +97,7 @@ static bool ovl_is_opaquedir(struct dentry *dentry)
static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
const char *name, unsigned int namelen,
+ size_t prelen, const char *post,
struct dentry **ret)
{
struct dentry *this;
@@ -74,6 +134,9 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
d->stop = d->opaque = true;
goto out;
}
+ err = ovl_check_redirect(this, d, prelen, post);
+ if (err)
+ goto out_err;
out:
*ret = this;
return 0;
@@ -91,7 +154,32 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
struct dentry **ret)
{
- return ovl_lookup_single(base, d, d->name.name, d->name.len, ret);
+ const char *s = d->name.name;
+ struct dentry *dentry = NULL;
+ int err;
+
+ if (*s != '/')
+ return ovl_lookup_single(base, d, d->name.name, d->name.len,
+ 0, "", ret);
+
+ while (*s++ == '/' && !IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
+ const char *next = strchrnul(s, '/');
+ size_t slen = strlen(s);
+
+ if (WARN_ON(slen > d->name.len) ||
+ WARN_ON(strcmp(d->name.name + d->name.len - slen, s)))
+ return -EIO;
+
+ err = ovl_lookup_single(base, d, s, next - s,
+ d->name.len - slen, next, &base);
+ dput(dentry);
+ if (err)
+ return err;
+ dentry = base;
+ s = next;
+ }
+ *ret = dentry;
+ return 0;
}
/*
@@ -127,6 +215,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
unsigned int ctr = 0;
struct inode *inode = NULL;
bool upperopaque = false;
+ char *upperredirect = NULL;
struct dentry *this;
unsigned int i;
int err;
@@ -136,6 +225,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
.opaque = false,
.stop = false,
.last = !poe->numlower,
+ .redirect = NULL,
};
if (dentry->d_name.len > ofs->namelen)
@@ -153,12 +243,20 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
err = -EREMOTE;
goto out;
}
+
+ if (d.redirect) {
+ upperredirect = kstrdup(d.redirect, GFP_KERNEL);
+ if (!upperredirect)
+ goto out_put_upper;
+ if (d.redirect[0] == '/')
+ poe = dentry->d_sb->s_root->d_fsdata;
+ }
upperopaque = d.opaque;
}
if (!d.stop && poe->numlower) {
err = -ENOMEM;
- stack = kcalloc(poe->numlower, sizeof(struct path),
+ stack = kcalloc(ofs->numlower, sizeof(struct path),
GFP_TEMPORARY);
if (!stack)
goto out_put_upper;
@@ -178,6 +276,22 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
stack[ctr].dentry = this;
stack[ctr].mnt = lowerpath.mnt;
ctr++;
+
+ if (d.stop)
+ break;
+
+ if (d.redirect &&
+ d.redirect[0] == '/' &&
+ poe != dentry->d_sb->s_root->d_fsdata) {
+ poe = dentry->d_sb->s_root->d_fsdata;
+
+ /* Find the current layer on the root dentry */
+ for (i = 0; i < poe->numlower; i++)
+ if (poe->lowerstack[i].mnt == lowerpath.mnt)
+ break;
+ if (WARN_ON(i == poe->numlower))
+ break;
+ }
}
oe = ovl_alloc_entry(ctr);
@@ -208,9 +322,11 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
revert_creds(old_cred);
oe->opaque = upperopaque;
+ oe->redirect = upperredirect;
oe->__upperdentry = upperdentry;
memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
kfree(stack);
+ kfree(d.redirect);
dentry->d_fsdata = oe;
d_add(dentry, inode);
@@ -224,7 +340,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
kfree(stack);
out_put_upper:
dput(upperdentry);
+ kfree(upperredirect);
out:
+ kfree(d.redirect);
revert_creds(old_cred);
return ERR_PTR(err);
}
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index f6e4d3539a251661c072cf994cb0934732cfeffe..e76d9d529e64cbcdc8c0f0e0560e26a96e9baad4 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -19,6 +19,7 @@ enum ovl_path_type {
#define OVL_XATTR_PREFIX XATTR_TRUSTED_PREFIX "overlay."
#define OVL_XATTR_OPAQUE OVL_XATTR_PREFIX "opaque"
+#define OVL_XATTR_REDIRECT OVL_XATTR_PREFIX "redirect"
#define OVL_ISUPPER_MASK 1UL
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index b10745edfc9361256bc988baf26d591ae9f8495c..eb29882b6a54dda74287d618197039a46277ba06 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -35,6 +35,7 @@ struct ovl_entry {
union {
struct {
u64 version;
+ const char *redirect;
bool opaque;
};
struct rcu_head rcu;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index aadb25413e6e6a4e9dc20e46831be4a30b9f0ba1..4e44e865b716cb17cd9bcfb7470961d2926b95f5 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -37,6 +37,7 @@ static void ovl_dentry_release(struct dentry *dentry)
unsigned int i;
dput(oe->__upperdentry);
+ kfree(oe->redirect);
for (i = 0; i < oe->numlower; i++)
dput(oe->lowerstack[i].dentry);
kfree_rcu(oe, rcu);