From b10b85fe5149ee8b39fbbf86095b303632dde2cd Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Wed, 27 Jul 2022 16:31:30 +0200
Subject: [PATCH] ovl: warn if trusted xattr creation fails
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.
Reported-by: Alois Wohlschlager <alois1@gmx-topmail.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/overlayfs/super.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 1ce5c96983937..4c20961302094 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1418,11 +1418,12 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
*/
err = ovl_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.
@@ -1430,8 +1431,10 @@ 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_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
--
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