On Thu, Feb 03, 2022 at 12:02:46PM +0100, Alois Wohlschlager wrote:
> When mounting overlayfs in an unprivileged user namespace, trusted xattr
> creation will fail. This will lead to failures in some file operations,
> e.g. in the following situation:
>
> mkdir lower upper work merged
> mkdir lower/directory
> mount -toverlay -olowerdir=lower,upperdir=upper,workdir=work none merged
> rmdir merged/directory
> mkdir merged/directory
>
> The last mkdir will fail:
>
> mkdir: cannot create directory 'merged/directory': Input/output error
>
> The cause for these failures is currently extremely non-obvious and hard
> to debug. Hence, warn the user and suggest using the userxattr mount
> option, if it is not already supplied and xattr creation fails during
> the self-check.
Thanks for the patch.
How about the following (untested) variant?
Thanks,
Miklos
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 7bb0a47cb615..955aeefc3b29 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1413,11 +1413,12 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
*/
err = ovl_do_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
if (err) {
+ pr_warn("failed to set xattr on upper\n");
ofs->noxattr = true;
if (ofs->config.index || ofs->config.metacopy) {
ofs->config.index = false;
ofs->config.metacopy = false;
- pr_warn("upper fs does not support xattr, falling back to index=off,metacopy=off.\n");
+ pr_warn("...falling back to index=off,metacopy=off.\n");
}
/*
* xattr support is required for persistent st_ino.
@@ -1425,8 +1426,10 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
*/
if (ofs->config.xino == OVL_XINO_AUTO) {
ofs->config.xino = OVL_XINO_OFF;
- pr_warn("upper fs does not support xattr, falling back to xino=off.\n");
+ pr_warn("...falling back to xino=off.\n");
}
+ if (err == -EPERM && !ofs->config.userxattr)
+ pr_info("try mounting with 'userxattr' option\n");
err = 0;
} else {
ovl_do_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
