From c846af050f944d584f28bc0de310383003c8096d Mon Sep 17 00:00:00 2001 From: Miklos Szeredi <mszeredi@redhat.com> Date: Mon, 14 Dec 2020 15:26:14 +0100 Subject: ovl: check privs before decoding file handle CAP_DAC_READ_SEARCH is required by open_by_handle_at(2) so check it in ovl_decode_real_fh() as well to prevent privilege escalation for unprivileged overlay mounts. [Amir] If the mounter is not capable in init ns, ovl_check_origin() and ovl_verify_index() will not function as expected and this will break index and nfs export features. So check capability in ovl_can_decode_fh(), to auto disable those features. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/overlayfs/util.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/overlayfs/util.c') diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index 44b4b62a8ac8..ced63c79e9dd 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -50,6 +50,9 @@ const struct cred *ovl_override_creds(struct super_block *sb) */ int ovl_can_decode_fh(struct super_block *sb) { + if (!capable(CAP_DAC_READ_SEARCH)) + return 0; + if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry) return 0; -- cgit v1.2.3