From: Miklos Szeredi mszeredi@redhat.com
[ Upstream commit b10b85fe5149ee8b39fbbf86095b303632dde2cd ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 001cdbb8f015..f3c13eca5270 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);