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-rw-r--r--fs/overlayfs/namei.c125
1 files changed, 93 insertions, 32 deletions
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index c6c79753b3b3..881caa385a36 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -84,7 +84,19 @@ invalid:
static int ovl_acceptable(void *ctx, struct dentry *dentry)
{
- return 1;
+ /*
+ * A non-dir origin may be disconnected, which is fine, because
+ * we only need it for its unique inode number.
+ */
+ if (!d_is_dir(dentry))
+ return 1;
+
+ /* Don't decode a deleted empty directory */
+ if (d_unhashed(dentry))
+ return 0;
+
+ /* Check if directory belongs to the layer we are decoding from */
+ return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root);
}
/*
@@ -160,7 +172,7 @@ invalid:
static struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
{
- struct dentry *origin;
+ struct dentry *real;
int bytes;
/*
@@ -171,22 +183,28 @@ static struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
return NULL;
bytes = (fh->len - offsetof(struct ovl_fh, fid));
- origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
- bytes >> 2, (int)fh->type,
- ovl_acceptable, NULL);
- if (IS_ERR(origin)) {
- /* Treat stale file handle as "origin unknown" */
- if (origin == ERR_PTR(-ESTALE))
- origin = NULL;
- return origin;
+ real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
+ bytes >> 2, (int)fh->type,
+ ovl_acceptable, mnt);
+ if (IS_ERR(real)) {
+ /*
+ * Treat stale file handle to lower file as "origin unknown".
+ * upper file handle could become stale when upper file is
+ * unlinked and this information is needed to handle stale
+ * index entries correctly.
+ */
+ if (real == ERR_PTR(-ESTALE) &&
+ !(fh->flags & OVL_FH_FLAG_PATH_UPPER))
+ real = NULL;
+ return real;
}
- if (ovl_dentry_weird(origin)) {
- dput(origin);
+ if (ovl_dentry_weird(real)) {
+ dput(real);
return NULL;
}
- return origin;
+ return real;
}
static bool ovl_is_opaquedir(struct dentry *dentry)
@@ -420,6 +438,35 @@ fail:
goto out;
}
+/* Get upper dentry from index */
+static 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_fh(fh, ofs->upper_mnt);
+ 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;
+}
+
/*
* 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.
@@ -431,23 +478,13 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
size_t len;
struct ovl_path origin = { };
struct ovl_path *stack = &origin;
+ struct dentry *upper = NULL;
int err;
if (!d_inode(index))
return 0;
- /*
- * Directory index entries are going to be used for looking up
- * redirected upper dirs by lower dir fh when decoding an overlay
- * file handle of a merge dir. We don't know the verification rules
- * for directory index entries, because they have not been implemented
- * yet, so return EINVAL if those entries are found to abort the mount
- * and to avoid corrupting an index that was created by a newer kernel.
- */
err = -EINVAL;
- if (d_is_dir(index))
- goto fail;
-
if (index->d_name.len < sizeof(struct ovl_fh)*2)
goto fail;
@@ -473,21 +510,45 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
if (ovl_is_whiteout(index))
goto out;
- err = ovl_verify_fh(index, OVL_XATTR_ORIGIN, fh);
- if (err)
+ /*
+ * 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);
+ if (!err)
+ err = -ESTALE;
goto fail;
+ }
- err = ovl_check_origin_fh(ofs, fh, index, &stack);
+ err = ovl_verify_fh(upper, OVL_XATTR_ORIGIN, fh);
+ dput(upper);
if (err)
goto fail;
- /* Check if index is orphan and don't warn before cleaning it */
- if (d_inode(index)->i_nlink == 1 &&
- ovl_get_nlink(origin.dentry, index, 0) == 0)
- err = -ENOENT;
+ /* 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, index, &stack);
+ if (err)
+ goto fail;
+
+ if (ovl_get_nlink(origin.dentry, index, 0) == 0)
+ err = -ENOENT;
+ }
- dput(origin.dentry);
out:
+ dput(origin.dentry);
kfree(fh);
return err;