From mboxrd@z Thu Jan 1 00:00:00 1970 From: Serge Hallyn Subject: [PATCH 9/9] make net/core/scm.c uid comparisons user namespace aware Date: Tue, 18 Oct 2011 21:54:58 +0000 Message-ID: <1318974898-21431-10-git-send-email-serge@hallyn.com> References: <1318974898-21431-1-git-send-email-serge@hallyn.com> Cc: ebiederm@xmission.com, akpm@linux-foundation.org, oleg@redhat.com, richard@nod.at, mikevs@xs4all.net, segoon@openwall.com, gregkh@suse.de, dhowells@redhat.com, eparis@redhat.com, "Serge E. Hallyn" , netdev@vger.kernel.org To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1318974898-21431-1-git-send-email-serge@hallyn.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: "Serge E. Hallyn" Currently uids are compared without regard for the user namespace. Fix that to prevent tasks in a different user namespace from wrongly matching on SCM_CREDENTIALS. In the past, either your uids had to match, or you had to have CAP_SETXID. In a namespaced world, you must either (both be in the same user namespace and have your uids match), or you must have CAP_SETXID targeted at the other user namespace. The latter can happen for instance if uid 500 created a new user namespace and now interacts with uid 0 in it. Signed-off-by: Serge E. Hallyn Cc: Eric W. Biederman Cc: netdev@vger.kernel.org --- net/core/scm.c | 41 ++++++++++++++++++++++++++++++++++------- 1 files changed, 34 insertions(+), 7 deletions(-) diff --git a/net/core/scm.c b/net/core/scm.c index 811b53f..4f376bf 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -43,17 +43,44 @@ * setu(g)id. */ -static __inline__ int scm_check_creds(struct ucred *creds) +static __inline__ bool uidequiv(const struct cred *src, struct ucred *tgt, + struct user_namespace *ns) +{ + if (src->user_ns != ns) + goto check_capable; + if (src->uid == tgt->uid || src->euid == tgt->uid || + src->suid == tgt->uid) + return true; +check_capable: + if (ns_capable(ns, CAP_SETUID)) + return true; + return false; +} + +static __inline__ bool gidequiv(const struct cred *src, struct ucred *tgt, + struct user_namespace *ns) +{ + if (src->user_ns != ns) + goto check_capable; + if (src->gid == tgt->gid || src->egid == tgt->gid || + src->sgid == tgt->gid) + return true; +check_capable: + if (ns_capable(ns, CAP_SETGID)) + return true; + return false; +} + +static __inline__ int scm_check_creds(struct ucred *creds, struct socket *sock) { const struct cred *cred = current_cred(); + struct user_namespace *ns = sock_net(sock->sk)->user_ns; - if ((creds->pid == task_tgid_vnr(current) || capable(CAP_SYS_ADMIN)) && - ((creds->uid == cred->uid || creds->uid == cred->euid || - creds->uid == cred->suid) || capable(CAP_SETUID)) && - ((creds->gid == cred->gid || creds->gid == cred->egid || - creds->gid == cred->sgid) || capable(CAP_SETGID))) { + if ((creds->pid == task_tgid_vnr(current) || ns_capable(ns, CAP_SYS_ADMIN)) && + uidequiv(cred, creds, ns) && gidequiv(cred, creds, ns)) { return 0; } + return -EPERM; } @@ -169,7 +196,7 @@ int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *p) if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred))) goto error; memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred)); - err = scm_check_creds(&p->creds); + err = scm_check_creds(&p->creds, sock); if (err) goto error; -- 1.7.5.4