1098 lines
26 KiB
C
1098 lines
26 KiB
C
/*
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* Copyright (C) 2011 Novell Inc.
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* Copyright (C) 2016 Red Hat, Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <linux/fs.h>
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#include <linux/cred.h>
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#include <linux/ctype.h>
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#include <linux/namei.h>
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#include <linux/xattr.h>
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#include <linux/ratelimit.h>
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#include <linux/mount.h>
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#include <linux/exportfs.h>
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#include "overlayfs.h"
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struct ovl_lookup_data {
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struct qstr name;
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bool is_dir;
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bool opaque;
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bool stop;
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bool last;
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char *redirect;
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};
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static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
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size_t prelen, const char *post)
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{
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int res;
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char *s, *next, *buf = NULL;
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res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
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if (res < 0) {
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if (res == -ENODATA || res == -EOPNOTSUPP)
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return 0;
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goto fail;
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}
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buf = kzalloc(prelen + res + strlen(post) + 1, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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if (res == 0)
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goto invalid;
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res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
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if (res < 0)
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goto fail;
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if (res == 0)
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goto invalid;
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if (buf[0] == '/') {
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for (s = buf; *s++ == '/'; s = next) {
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next = strchrnul(s, '/');
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if (s == next)
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goto invalid;
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}
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/*
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* One of the ancestor path elements in an absolute path
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* lookup in ovl_lookup_layer() could have been opaque and
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* that will stop further lookup in lower layers (d->stop=true)
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* But we have found an absolute redirect in decendant path
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* element and that should force continue lookup in lower
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* layers (reset d->stop).
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*/
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d->stop = false;
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} else {
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if (strchr(buf, '/') != NULL)
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goto invalid;
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memmove(buf + prelen, buf, res);
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memcpy(buf, d->name.name, prelen);
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}
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strcat(buf, post);
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kfree(d->redirect);
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d->redirect = buf;
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d->name.name = d->redirect;
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d->name.len = strlen(d->redirect);
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return 0;
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err_free:
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kfree(buf);
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return 0;
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fail:
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pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
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goto err_free;
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invalid:
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pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
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goto err_free;
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}
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static int ovl_acceptable(void *ctx, struct dentry *dentry)
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{
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/*
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* A non-dir origin may be disconnected, which is fine, because
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* we only need it for its unique inode number.
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*/
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if (!d_is_dir(dentry))
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return 1;
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/* Don't decode a deleted empty directory */
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if (d_unhashed(dentry))
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return 0;
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/* Check if directory belongs to the layer we are decoding from */
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return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root);
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}
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/*
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* Check validity of an overlay file handle buffer.
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*
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* Return 0 for a valid file handle.
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* Return -ENODATA for "origin unknown".
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* Return <0 for an invalid file handle.
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*/
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int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
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{
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if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len)
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return -EINVAL;
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if (fh->magic != OVL_FH_MAGIC)
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return -EINVAL;
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/* Treat larger version and unknown flags as "origin unknown" */
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if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
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return -ENODATA;
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/* Treat endianness mismatch as "origin unknown" */
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if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
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(fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
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return -ENODATA;
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return 0;
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}
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static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
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{
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int res, err;
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struct ovl_fh *fh = NULL;
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res = vfs_getxattr(dentry, name, NULL, 0);
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if (res < 0) {
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if (res == -ENODATA || res == -EOPNOTSUPP)
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return NULL;
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goto fail;
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}
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/* Zero size value means "copied up but origin unknown" */
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if (res == 0)
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return NULL;
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fh = kzalloc(res, GFP_KERNEL);
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if (!fh)
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return ERR_PTR(-ENOMEM);
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res = vfs_getxattr(dentry, name, fh, res);
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if (res < 0)
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goto fail;
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err = ovl_check_fh_len(fh, res);
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if (err < 0) {
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if (err == -ENODATA)
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goto out;
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goto invalid;
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}
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return fh;
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out:
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kfree(fh);
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return NULL;
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fail:
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pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);
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goto out;
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invalid:
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pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);
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goto out;
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}
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struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
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bool connected)
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{
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struct dentry *real;
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int bytes;
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/*
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* Make sure that the stored uuid matches the uuid of the lower
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* layer where file handle will be decoded.
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*/
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if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
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return NULL;
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bytes = (fh->len - offsetof(struct ovl_fh, fid));
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real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
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bytes >> 2, (int)fh->type,
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connected ? ovl_acceptable : NULL, mnt);
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if (IS_ERR(real)) {
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/*
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* Treat stale file handle to lower file as "origin unknown".
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* upper file handle could become stale when upper file is
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* unlinked and this information is needed to handle stale
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* index entries correctly.
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*/
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if (real == ERR_PTR(-ESTALE) &&
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!(fh->flags & OVL_FH_FLAG_PATH_UPPER))
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real = NULL;
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return real;
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}
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if (ovl_dentry_weird(real)) {
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dput(real);
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return NULL;
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}
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return real;
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}
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static bool ovl_is_opaquedir(struct dentry *dentry)
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{
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return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE);
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}
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static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
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const char *name, unsigned int namelen,
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size_t prelen, const char *post,
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struct dentry **ret)
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{
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struct dentry *this;
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int err;
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bool last_element = !post[0];
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this = lookup_one_len_unlocked(name, base, namelen);
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if (IS_ERR(this)) {
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err = PTR_ERR(this);
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this = NULL;
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if (err == -ENOENT || err == -ENAMETOOLONG)
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goto out;
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goto out_err;
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}
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if (!this->d_inode)
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goto put_and_out;
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if (ovl_dentry_weird(this)) {
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/* Don't support traversing automounts and other weirdness */
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err = -EREMOTE;
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goto out_err;
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}
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if (ovl_is_whiteout(this)) {
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d->stop = d->opaque = true;
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goto put_and_out;
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}
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if (!d_can_lookup(this)) {
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d->stop = true;
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if (d->is_dir)
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goto put_and_out;
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/*
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* NB: handle failure to lookup non-last element when non-dir
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* redirects become possible
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*/
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WARN_ON(!last_element);
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goto out;
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}
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if (last_element)
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d->is_dir = true;
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if (d->last)
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goto out;
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if (ovl_is_opaquedir(this)) {
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d->stop = true;
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if (last_element)
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d->opaque = true;
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goto out;
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}
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err = ovl_check_redirect(this, d, prelen, post);
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if (err)
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goto out_err;
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out:
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*ret = this;
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return 0;
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put_and_out:
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dput(this);
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this = NULL;
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goto out;
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out_err:
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dput(this);
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return err;
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}
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static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
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struct dentry **ret)
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{
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/* Counting down from the end, since the prefix can change */
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size_t rem = d->name.len - 1;
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struct dentry *dentry = NULL;
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int err;
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if (d->name.name[0] != '/')
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return ovl_lookup_single(base, d, d->name.name, d->name.len,
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0, "", ret);
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while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
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const char *s = d->name.name + d->name.len - rem;
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const char *next = strchrnul(s, '/');
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size_t thislen = next - s;
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bool end = !next[0];
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/* Verify we did not go off the rails */
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if (WARN_ON(s[-1] != '/'))
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return -EIO;
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err = ovl_lookup_single(base, d, s, thislen,
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d->name.len - rem, next, &base);
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dput(dentry);
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if (err)
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return err;
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dentry = base;
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if (end)
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break;
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rem -= thislen + 1;
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if (WARN_ON(rem >= d->name.len))
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return -EIO;
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}
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*ret = dentry;
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return 0;
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}
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int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
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struct dentry *upperdentry, struct ovl_path **stackp)
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{
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struct dentry *origin = NULL;
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int i;
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for (i = 0; i < ofs->numlower; i++) {
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origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt,
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connected);
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if (origin)
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break;
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}
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if (!origin)
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return -ESTALE;
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else if (IS_ERR(origin))
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return PTR_ERR(origin);
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if (upperdentry && !ovl_is_whiteout(upperdentry) &&
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((d_inode(origin)->i_mode ^ d_inode(upperdentry)->i_mode) & S_IFMT))
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goto invalid;
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if (!*stackp)
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*stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL);
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if (!*stackp) {
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dput(origin);
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return -ENOMEM;
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}
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**stackp = (struct ovl_path){
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.dentry = origin,
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.layer = &ofs->lower_layers[i]
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};
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return 0;
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invalid:
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pr_warn_ratelimited("overlayfs: invalid origin (%pd2, ftype=%x, origin ftype=%x).\n",
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upperdentry, d_inode(upperdentry)->i_mode & S_IFMT,
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d_inode(origin)->i_mode & S_IFMT);
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dput(origin);
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return -EIO;
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}
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|
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static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
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struct ovl_path **stackp, unsigned int *ctrp)
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{
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struct ovl_fh *fh = ovl_get_fh(upperdentry, OVL_XATTR_ORIGIN);
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int err;
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|
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if (IS_ERR_OR_NULL(fh))
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return PTR_ERR(fh);
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|
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err = ovl_check_origin_fh(ofs, fh, false, upperdentry, stackp);
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kfree(fh);
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if (err) {
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if (err == -ESTALE)
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return 0;
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return err;
|
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}
|
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|
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if (WARN_ON(*ctrp))
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return -EIO;
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|
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*ctrp = 1;
|
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return 0;
|
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}
|
|
|
|
/*
|
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* Verify that @fh matches the file handle stored in xattr @name.
|
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* Return 0 on match, -ESTALE on mismatch, < 0 on error.
|
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*/
|
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static int ovl_verify_fh(struct dentry *dentry, const char *name,
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const struct ovl_fh *fh)
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{
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struct ovl_fh *ofh = ovl_get_fh(dentry, name);
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int err = 0;
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|
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if (!ofh)
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return -ENODATA;
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|
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if (IS_ERR(ofh))
|
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return PTR_ERR(ofh);
|
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|
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if (fh->len != ofh->len || memcmp(fh, ofh, fh->len))
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err = -ESTALE;
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|
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kfree(ofh);
|
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return err;
|
|
}
|
|
|
|
/*
|
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* Verify that @real dentry matches the file handle stored in xattr @name.
|
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*
|
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* If @set is true and there is no stored file handle, encode @real and store
|
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* file handle in xattr @name.
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*
|
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* Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
|
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*/
|
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int ovl_verify_set_fh(struct dentry *dentry, const char *name,
|
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struct dentry *real, bool is_upper, bool set)
|
|
{
|
|
struct inode *inode;
|
|
struct ovl_fh *fh;
|
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int err;
|
|
|
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fh = ovl_encode_real_fh(real, is_upper);
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err = PTR_ERR(fh);
|
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if (IS_ERR(fh))
|
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goto fail;
|
|
|
|
err = ovl_verify_fh(dentry, name, fh);
|
|
if (set && err == -ENODATA)
|
|
err = ovl_do_setxattr(dentry, name, fh, fh->len, 0);
|
|
if (err)
|
|
goto fail;
|
|
|
|
out:
|
|
kfree(fh);
|
|
return err;
|
|
|
|
fail:
|
|
inode = d_inode(real);
|
|
pr_warn_ratelimited("overlayfs: failed to verify %s (%pd2, ino=%lu, err=%i)\n",
|
|
is_upper ? "upper" : "origin", real,
|
|
inode ? inode->i_ino : 0, err);
|
|
goto out;
|
|
}
|
|
|
|
/* Get upper dentry from index */
|
|
struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
|
|
{
|
|
struct ovl_fh *fh;
|
|
struct dentry *upper;
|
|
|
|
if (!d_is_dir(index))
|
|
return dget(index);
|
|
|
|
fh = ovl_get_fh(index, OVL_XATTR_UPPER);
|
|
if (IS_ERR_OR_NULL(fh))
|
|
return ERR_CAST(fh);
|
|
|
|
upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);
|
|
kfree(fh);
|
|
|
|
if (IS_ERR_OR_NULL(upper))
|
|
return upper ?: ERR_PTR(-ESTALE);
|
|
|
|
if (!d_is_dir(upper)) {
|
|
pr_warn_ratelimited("overlayfs: invalid index upper (%pd2, upper=%pd2).\n",
|
|
index, upper);
|
|
dput(upper);
|
|
return ERR_PTR(-EIO);
|
|
}
|
|
|
|
return upper;
|
|
}
|
|
|
|
/* Is this a leftover from create/whiteout of directory index entry? */
|
|
static bool ovl_is_temp_index(struct dentry *index)
|
|
{
|
|
return index->d_name.name[0] == '#';
|
|
}
|
|
|
|
/*
|
|
* Verify that an index entry name matches the origin file handle stored in
|
|
* OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
|
|
* Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
|
|
*/
|
|
int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
|
|
{
|
|
struct ovl_fh *fh = NULL;
|
|
size_t len;
|
|
struct ovl_path origin = { };
|
|
struct ovl_path *stack = &origin;
|
|
struct dentry *upper = NULL;
|
|
int err;
|
|
|
|
if (!d_inode(index))
|
|
return 0;
|
|
|
|
/* Cleanup leftover from index create/cleanup attempt */
|
|
err = -ESTALE;
|
|
if (ovl_is_temp_index(index))
|
|
goto fail;
|
|
|
|
err = -EINVAL;
|
|
if (index->d_name.len < sizeof(struct ovl_fh)*2)
|
|
goto fail;
|
|
|
|
err = -ENOMEM;
|
|
len = index->d_name.len / 2;
|
|
fh = kzalloc(len, GFP_KERNEL);
|
|
if (!fh)
|
|
goto fail;
|
|
|
|
err = -EINVAL;
|
|
if (hex2bin((u8 *)fh, index->d_name.name, len))
|
|
goto fail;
|
|
|
|
err = ovl_check_fh_len(fh, len);
|
|
if (err)
|
|
goto fail;
|
|
|
|
/*
|
|
* Whiteout index entries are used as an indication that an exported
|
|
* overlay file handle should be treated as stale (i.e. after unlink
|
|
* of the overlay inode). These entries contain no origin xattr.
|
|
*/
|
|
if (ovl_is_whiteout(index))
|
|
goto out;
|
|
|
|
/*
|
|
* Verifying directory index entries are not stale is expensive, so
|
|
* only verify stale dir index if NFS export is enabled.
|
|
*/
|
|
if (d_is_dir(index) && !ofs->config.nfs_export)
|
|
goto out;
|
|
|
|
/*
|
|
* Directory index entries should have 'upper' xattr pointing to the
|
|
* real upper dir. Non-dir index entries are hardlinks to the upper
|
|
* real inode. For non-dir index, we can read the copy up origin xattr
|
|
* directly from the index dentry, but for dir index we first need to
|
|
* decode the upper directory.
|
|
*/
|
|
upper = ovl_index_upper(ofs, index);
|
|
if (IS_ERR_OR_NULL(upper)) {
|
|
err = PTR_ERR(upper);
|
|
/*
|
|
* Directory index entries with no 'upper' xattr need to be
|
|
* removed. When dir index entry has a stale 'upper' xattr,
|
|
* we assume that upper dir was removed and we treat the dir
|
|
* index as orphan entry that needs to be whited out.
|
|
*/
|
|
if (err == -ESTALE)
|
|
goto orphan;
|
|
else if (!err)
|
|
err = -ESTALE;
|
|
goto fail;
|
|
}
|
|
|
|
err = ovl_verify_fh(upper, OVL_XATTR_ORIGIN, fh);
|
|
dput(upper);
|
|
if (err)
|
|
goto fail;
|
|
|
|
/* Check if non-dir index is orphan and don't warn before cleaning it */
|
|
if (!d_is_dir(index) && d_inode(index)->i_nlink == 1) {
|
|
err = ovl_check_origin_fh(ofs, fh, false, index, &stack);
|
|
if (err)
|
|
goto fail;
|
|
|
|
if (ovl_get_nlink(origin.dentry, index, 0) == 0)
|
|
goto orphan;
|
|
}
|
|
|
|
out:
|
|
dput(origin.dentry);
|
|
kfree(fh);
|
|
return err;
|
|
|
|
fail:
|
|
pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, ftype=%x, err=%i)\n",
|
|
index, d_inode(index)->i_mode & S_IFMT, err);
|
|
goto out;
|
|
|
|
orphan:
|
|
pr_warn_ratelimited("overlayfs: orphan index entry (%pd2, ftype=%x, nlink=%u)\n",
|
|
index, d_inode(index)->i_mode & S_IFMT,
|
|
d_inode(index)->i_nlink);
|
|
err = -ENOENT;
|
|
goto out;
|
|
}
|
|
|
|
static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name)
|
|
{
|
|
char *n, *s;
|
|
|
|
n = kzalloc(fh->len * 2, GFP_KERNEL);
|
|
if (!n)
|
|
return -ENOMEM;
|
|
|
|
s = bin2hex(n, fh, fh->len);
|
|
*name = (struct qstr) QSTR_INIT(n, s - n);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
/*
|
|
* Lookup in indexdir for the index entry of a lower real inode or a copy up
|
|
* origin inode. The index entry name is the hex representation of the lower
|
|
* inode file handle.
|
|
*
|
|
* If the index dentry in negative, then either no lower aliases have been
|
|
* copied up yet, or aliases have been copied up in older kernels and are
|
|
* not indexed.
|
|
*
|
|
* If the index dentry for a copy up origin inode is positive, but points
|
|
* to an inode different than the upper inode, then either the upper inode
|
|
* has been copied up and not indexed or it was indexed, but since then
|
|
* index dir was cleared. Either way, that index cannot be used to indentify
|
|
* the overlay inode.
|
|
*/
|
|
int ovl_get_index_name(struct dentry *origin, struct qstr *name)
|
|
{
|
|
struct ovl_fh *fh;
|
|
int err;
|
|
|
|
fh = ovl_encode_real_fh(origin, false);
|
|
if (IS_ERR(fh))
|
|
return PTR_ERR(fh);
|
|
|
|
err = ovl_get_index_name_fh(fh, name);
|
|
|
|
kfree(fh);
|
|
return err;
|
|
}
|
|
|
|
/* Lookup index by file handle for NFS export */
|
|
struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
|
|
{
|
|
struct dentry *index;
|
|
struct qstr name;
|
|
int err;
|
|
|
|
err = ovl_get_index_name_fh(fh, &name);
|
|
if (err)
|
|
return ERR_PTR(err);
|
|
|
|
index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
|
|
kfree(name.name);
|
|
if (IS_ERR(index)) {
|
|
if (PTR_ERR(index) == -ENOENT)
|
|
index = NULL;
|
|
return index;
|
|
}
|
|
|
|
if (d_is_negative(index))
|
|
err = 0;
|
|
else if (ovl_is_whiteout(index))
|
|
err = -ESTALE;
|
|
else if (ovl_dentry_weird(index))
|
|
err = -EIO;
|
|
else
|
|
return index;
|
|
|
|
dput(index);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
|
|
struct dentry *origin, bool verify)
|
|
{
|
|
struct dentry *index;
|
|
struct inode *inode;
|
|
struct qstr name;
|
|
bool is_dir = d_is_dir(origin);
|
|
int err;
|
|
|
|
err = ovl_get_index_name(origin, &name);
|
|
if (err)
|
|
return ERR_PTR(err);
|
|
|
|
index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
|
|
if (IS_ERR(index)) {
|
|
err = PTR_ERR(index);
|
|
if (err == -ENOENT) {
|
|
index = NULL;
|
|
goto out;
|
|
}
|
|
pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%*s, err=%i);\n"
|
|
"overlayfs: mount with '-o index=off' to disable inodes index.\n",
|
|
d_inode(origin)->i_ino, name.len, name.name,
|
|
err);
|
|
goto out;
|
|
}
|
|
|
|
inode = d_inode(index);
|
|
if (d_is_negative(index)) {
|
|
goto out_dput;
|
|
} else if (ovl_is_whiteout(index) && !verify) {
|
|
/*
|
|
* When index lookup is called with !verify for decoding an
|
|
* overlay file handle, a whiteout index implies that decode
|
|
* should treat file handle as stale and no need to print a
|
|
* warning about it.
|
|
*/
|
|
dput(index);
|
|
index = ERR_PTR(-ESTALE);
|
|
goto out;
|
|
} else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
|
|
((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
|
|
/*
|
|
* Index should always be of the same file type as origin
|
|
* except for the case of a whiteout index. A whiteout
|
|
* index should only exist if all lower aliases have been
|
|
* unlinked, which means that finding a lower origin on lookup
|
|
* whose index is a whiteout should be treated as an error.
|
|
*/
|
|
pr_warn_ratelimited("overlayfs: bad index found (index=%pd2, ftype=%x, origin ftype=%x).\n",
|
|
index, d_inode(index)->i_mode & S_IFMT,
|
|
d_inode(origin)->i_mode & S_IFMT);
|
|
goto fail;
|
|
} else if (is_dir && verify) {
|
|
if (!upper) {
|
|
pr_warn_ratelimited("overlayfs: suspected uncovered redirected dir found (origin=%pd2, index=%pd2).\n",
|
|
origin, index);
|
|
goto fail;
|
|
}
|
|
|
|
/* Verify that dir index 'upper' xattr points to upper dir */
|
|
err = ovl_verify_upper(index, upper, false);
|
|
if (err) {
|
|
if (err == -ESTALE) {
|
|
pr_warn_ratelimited("overlayfs: suspected multiply redirected dir found (upper=%pd2, origin=%pd2, index=%pd2).\n",
|
|
upper, origin, index);
|
|
}
|
|
goto fail;
|
|
}
|
|
} else if (upper && d_inode(upper) != inode) {
|
|
goto out_dput;
|
|
}
|
|
out:
|
|
kfree(name.name);
|
|
return index;
|
|
|
|
out_dput:
|
|
dput(index);
|
|
index = NULL;
|
|
goto out;
|
|
|
|
fail:
|
|
dput(index);
|
|
index = ERR_PTR(-EIO);
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Returns next layer in stack starting from top.
|
|
* Returns -1 if this is the last layer.
|
|
*/
|
|
int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
|
|
{
|
|
struct ovl_entry *oe = dentry->d_fsdata;
|
|
|
|
BUG_ON(idx < 0);
|
|
if (idx == 0) {
|
|
ovl_path_upper(dentry, path);
|
|
if (path->dentry)
|
|
return oe->numlower ? 1 : -1;
|
|
idx++;
|
|
}
|
|
BUG_ON(idx > oe->numlower);
|
|
path->dentry = oe->lowerstack[idx - 1].dentry;
|
|
path->mnt = oe->lowerstack[idx - 1].layer->mnt;
|
|
|
|
return (idx < oe->numlower) ? idx + 1 : -1;
|
|
}
|
|
|
|
/* Fix missing 'origin' xattr */
|
|
static int ovl_fix_origin(struct dentry *dentry, struct dentry *lower,
|
|
struct dentry *upper)
|
|
{
|
|
int err;
|
|
|
|
if (ovl_check_origin_xattr(upper))
|
|
return 0;
|
|
|
|
err = ovl_want_write(dentry);
|
|
if (err)
|
|
return err;
|
|
|
|
err = ovl_set_origin(dentry, lower, upper);
|
|
if (!err)
|
|
err = ovl_set_impure(dentry->d_parent, upper->d_parent);
|
|
|
|
ovl_drop_write(dentry);
|
|
return err;
|
|
}
|
|
|
|
struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
|
|
unsigned int flags)
|
|
{
|
|
struct ovl_entry *oe;
|
|
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_path *stack = NULL;
|
|
struct dentry *upperdir, *upperdentry = NULL;
|
|
struct dentry *origin = NULL;
|
|
struct dentry *index = NULL;
|
|
unsigned int ctr = 0;
|
|
struct inode *inode = NULL;
|
|
bool upperopaque = false;
|
|
char *upperredirect = NULL;
|
|
struct dentry *this;
|
|
unsigned int i;
|
|
int err;
|
|
struct ovl_lookup_data d = {
|
|
.name = dentry->d_name,
|
|
.is_dir = false,
|
|
.opaque = false,
|
|
.stop = false,
|
|
.last = ofs->config.redirect_follow ? false : !poe->numlower,
|
|
.redirect = NULL,
|
|
};
|
|
|
|
if (dentry->d_name.len > ofs->namelen)
|
|
return ERR_PTR(-ENAMETOOLONG);
|
|
|
|
old_cred = ovl_override_creds(dentry->d_sb);
|
|
upperdir = ovl_dentry_upper(dentry->d_parent);
|
|
if (upperdir) {
|
|
err = ovl_lookup_layer(upperdir, &d, &upperdentry);
|
|
if (err)
|
|
goto out;
|
|
|
|
if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
|
|
dput(upperdentry);
|
|
err = -EREMOTE;
|
|
goto out;
|
|
}
|
|
if (upperdentry && !d.is_dir) {
|
|
BUG_ON(!d.stop || d.redirect);
|
|
/*
|
|
* Lookup copy up origin by decoding origin file handle.
|
|
* We may get a disconnected dentry, which is fine,
|
|
* because we only need to hold the origin inode in
|
|
* cache and use its inode number. We may even get a
|
|
* connected dentry, that is not under any of the lower
|
|
* layers root. That is also fine for using it's inode
|
|
* number - it's the same as if we held a reference
|
|
* to a dentry in lower layer that was moved under us.
|
|
*/
|
|
err = ovl_check_origin(ofs, upperdentry, &stack, &ctr);
|
|
if (err)
|
|
goto out_put_upper;
|
|
}
|
|
|
|
if (d.redirect) {
|
|
err = -ENOMEM;
|
|
upperredirect = kstrdup(d.redirect, GFP_KERNEL);
|
|
if (!upperredirect)
|
|
goto out_put_upper;
|
|
if (d.redirect[0] == '/')
|
|
poe = roe;
|
|
}
|
|
upperopaque = d.opaque;
|
|
}
|
|
|
|
if (!d.stop && poe->numlower) {
|
|
err = -ENOMEM;
|
|
stack = kcalloc(ofs->numlower, sizeof(struct ovl_path),
|
|
GFP_KERNEL);
|
|
if (!stack)
|
|
goto out_put_upper;
|
|
}
|
|
|
|
for (i = 0; !d.stop && i < poe->numlower; i++) {
|
|
struct ovl_path lower = poe->lowerstack[i];
|
|
|
|
if (!ofs->config.redirect_follow)
|
|
d.last = i == poe->numlower - 1;
|
|
else
|
|
d.last = lower.layer->idx == roe->numlower;
|
|
|
|
err = ovl_lookup_layer(lower.dentry, &d, &this);
|
|
if (err)
|
|
goto out_put;
|
|
|
|
if (!this)
|
|
continue;
|
|
|
|
/*
|
|
* If no origin fh is stored in upper of a merge dir, store fh
|
|
* of lower dir and set upper parent "impure".
|
|
*/
|
|
if (upperdentry && !ctr && !ofs->noxattr) {
|
|
err = ovl_fix_origin(dentry, this, upperdentry);
|
|
if (err) {
|
|
dput(this);
|
|
goto out_put;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* When "verify_lower" feature is enabled, do not merge with a
|
|
* lower dir that does not match a stored origin xattr. In any
|
|
* case, only verified origin is used for index lookup.
|
|
*/
|
|
if (upperdentry && !ctr && ovl_verify_lower(dentry->d_sb)) {
|
|
err = ovl_verify_origin(upperdentry, this, false);
|
|
if (err) {
|
|
dput(this);
|
|
break;
|
|
}
|
|
|
|
/* Bless lower dir as verified origin */
|
|
origin = this;
|
|
}
|
|
|
|
stack[ctr].dentry = this;
|
|
stack[ctr].layer = lower.layer;
|
|
ctr++;
|
|
|
|
/*
|
|
* Following redirects can have security consequences: it's like
|
|
* a symlink into the lower layer without the permission checks.
|
|
* This is only a problem if the upper layer is untrusted (e.g
|
|
* comes from an USB drive). This can allow a non-readable file
|
|
* or directory to become readable.
|
|
*
|
|
* Only following redirects when redirects are enabled disables
|
|
* this attack vector when not necessary.
|
|
*/
|
|
err = -EPERM;
|
|
if (d.redirect && !ofs->config.redirect_follow) {
|
|
pr_warn_ratelimited("overlayfs: refusing to follow redirect for (%pd2)\n",
|
|
dentry);
|
|
goto out_put;
|
|
}
|
|
|
|
if (d.stop)
|
|
break;
|
|
|
|
if (d.redirect && d.redirect[0] == '/' && poe != roe) {
|
|
poe = roe;
|
|
/* Find the current layer on the root dentry */
|
|
i = lower.layer->idx - 1;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Lookup index by lower inode and verify it matches upper inode.
|
|
* We only trust dir index if we verified that lower dir matches
|
|
* origin, otherwise dir index entries may be inconsistent and we
|
|
* ignore them. Always lookup index of non-dir and non-upper.
|
|
*/
|
|
if (ctr && (!upperdentry || !d.is_dir))
|
|
origin = stack[0].dentry;
|
|
|
|
if (origin && ovl_indexdir(dentry->d_sb) &&
|
|
(!d.is_dir || ovl_index_all(dentry->d_sb))) {
|
|
index = ovl_lookup_index(ofs, upperdentry, origin, true);
|
|
if (IS_ERR(index)) {
|
|
err = PTR_ERR(index);
|
|
index = NULL;
|
|
goto out_put;
|
|
}
|
|
}
|
|
|
|
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;
|
|
|
|
if (upperopaque)
|
|
ovl_dentry_set_opaque(dentry);
|
|
|
|
if (upperdentry)
|
|
ovl_dentry_set_upper_alias(dentry);
|
|
else if (index)
|
|
upperdentry = dget(index);
|
|
|
|
if (upperdentry || ctr) {
|
|
inode = ovl_get_inode(dentry->d_sb, upperdentry, stack, index,
|
|
ctr);
|
|
err = PTR_ERR(inode);
|
|
if (IS_ERR(inode))
|
|
goto out_free_oe;
|
|
|
|
/*
|
|
* NB: handle redirected hard links when non-dir redirects
|
|
* become possible
|
|
*/
|
|
WARN_ON(OVL_I(inode)->redirect);
|
|
OVL_I(inode)->redirect = upperredirect;
|
|
}
|
|
|
|
revert_creds(old_cred);
|
|
dput(index);
|
|
kfree(stack);
|
|
kfree(d.redirect);
|
|
return d_splice_alias(inode, dentry);
|
|
|
|
out_free_oe:
|
|
dentry->d_fsdata = NULL;
|
|
kfree(oe);
|
|
out_put:
|
|
dput(index);
|
|
for (i = 0; i < ctr; i++)
|
|
dput(stack[i].dentry);
|
|
kfree(stack);
|
|
out_put_upper:
|
|
dput(upperdentry);
|
|
kfree(upperredirect);
|
|
out:
|
|
kfree(d.redirect);
|
|
revert_creds(old_cred);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
bool ovl_lower_positive(struct dentry *dentry)
|
|
{
|
|
struct ovl_entry *poe = dentry->d_parent->d_fsdata;
|
|
const struct qstr *name = &dentry->d_name;
|
|
const struct cred *old_cred;
|
|
unsigned int i;
|
|
bool positive = false;
|
|
bool done = false;
|
|
|
|
/*
|
|
* If dentry is negative, then lower is positive iff this is a
|
|
* whiteout.
|
|
*/
|
|
if (!dentry->d_inode)
|
|
return ovl_dentry_is_opaque(dentry);
|
|
|
|
/* Negative upper -> positive lower */
|
|
if (!ovl_dentry_upper(dentry))
|
|
return true;
|
|
|
|
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++) {
|
|
struct dentry *this;
|
|
struct dentry *lowerdir = poe->lowerstack[i].dentry;
|
|
|
|
this = lookup_one_len_unlocked(name->name, lowerdir,
|
|
name->len);
|
|
if (IS_ERR(this)) {
|
|
switch (PTR_ERR(this)) {
|
|
case -ENOENT:
|
|
case -ENAMETOOLONG:
|
|
break;
|
|
|
|
default:
|
|
/*
|
|
* Assume something is there, we just couldn't
|
|
* access it.
|
|
*/
|
|
positive = true;
|
|
break;
|
|
}
|
|
} else {
|
|
if (this->d_inode) {
|
|
positive = !ovl_is_whiteout(this);
|
|
done = true;
|
|
}
|
|
dput(this);
|
|
}
|
|
}
|
|
revert_creds(old_cred);
|
|
|
|
return positive;
|
|
}
|