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ovl: warn if trusted xattr creation fails

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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>
This commit is contained in:
Miklos Szeredi 2022-07-27 16:31:30 +02:00
parent e0dccc3b76
commit b10b85fe51
1 changed files with 5 additions and 2 deletions
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7
fs/overlayfs/super.c
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@ -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); err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
if (err) { if (err) {
pr_warn("failed to set xattr on upper\n");
ofs->noxattr = true; ofs->noxattr = true;
if (ofs->config.index || ofs->config.metacopy) { if (ofs->config.index || ofs->config.metacopy) {
ofs->config.index = false; ofs->config.index = false;
ofs->config.metacopy = 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. * 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) { if (ofs->config.xino == OVL_XINO_AUTO) {
ofs->config.xino = OVL_XINO_OFF; 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; err = 0;
} else { } else {
ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE); ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);