Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932538AbaJNO10 (ORCPT ); Tue, 14 Oct 2014 10:27:26 -0400 Received: from mail-oi0-f49.google.com ([209.85.218.49]:61929 "EHLO mail-oi0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932425AbaJNO0N (ORCPT ); Tue, 14 Oct 2014 10:26:13 -0400 From: Seth Forshee To: Miklos Szeredi Cc: fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Seth Forshee , "Eric W. Biederman" , "Serge H. Hallyn" Subject: [PATCH v4 3/5] fuse: Restrict allow_other to uids already controlled by the user Date: Tue, 14 Oct 2014 16:25:54 +0200 Message-Id: <1413296756-25071-4-git-send-email-seth.forshee@canonical.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1413296756-25071-1-git-send-email-seth.forshee@canonical.com> References: <1413296756-25071-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Unprivileged users are normally restricted from mounting with the allow_other option by system policy, but this could be bypassed for a mount done with user namespace root permissions. In such cases allow_other should not allow users outside the user namespace to access the mount as doing so would give the unprivileged user the ability to manipulate processes it would otherwise be unable to manipulate. Cc: Eric W. Biederman Cc: Serge H. Hallyn Signed-off-by: Seth Forshee --- fs/fuse/dir.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 123db1e06c78..e3123bfbc711 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1089,12 +1089,20 @@ int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid, */ int fuse_allow_current_process(struct fuse_conn *fc) { - const struct cred *cred; + const struct cred *cred = current_cred(); - if (fc->flags & FUSE_ALLOW_OTHER) - return 1; + if (fc->flags & FUSE_ALLOW_OTHER) { + if (kuid_has_mapping(fc->user_ns, cred->euid) && + kuid_has_mapping(fc->user_ns, cred->suid) && + kuid_has_mapping(fc->user_ns, cred->uid) && + kgid_has_mapping(fc->user_ns, cred->egid) && + kgid_has_mapping(fc->user_ns, cred->sgid) && + kgid_has_mapping(fc->user_ns, cred->gid)) + return 1; + + return 0; + } - cred = current_cred(); if (uid_eq(cred->euid, fc->user_id) && uid_eq(cred->suid, fc->user_id) && uid_eq(cred->uid, fc->user_id) && -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/