Messages in this thread Patch in this message | | | Date | Tue, 18 Oct 2011 21:25:52 -0500 | From | "Serge E. Hallyn" <> | Subject | [PATCH 9/9] make net/core/scm.c uid comparisons user namespace aware (v2) |
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(Thanks for the suggestions, Joe.)
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.
Changelog: Oct 18: Per Joe Perches: don't mark uidequiv and gidequiv fns inline (let the compiler do that if appropriate), and change the flow of id comparisons to make it clearer.
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Joe Perches <joe@perches.com> --- net/core/scm.c | 43 ++++++++++++++++++++++++++++++++++++------- 1 files changed, 36 insertions(+), 7 deletions(-)
diff --git a/net/core/scm.c b/net/core/scm.c index 811b53f..2261607 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -43,17 +43,46 @@ * setu(g)id. */ -static __inline__ int scm_check_creds(struct ucred *creds) +static bool uidequiv(const struct cred *src, struct ucred *tgt, + struct user_namespace *ns) +{ + if (src->user_ns != ns) + goto check_capable; + if (tgt->uid == src->uid || + tgt->uid == src->euid || + tgt->uid == src->suid) + return true; +check_capable: + if (ns_capable(ns, CAP_SETUID)) + return true; + return false; +} + +static bool gidequiv(const struct cred *src, struct ucred *tgt, + struct user_namespace *ns) +{ + if (src->user_ns != ns) + goto check_capable; + if (tgt->gid == src->gid || + tgt->gid == src->egid || + tgt->gid == src->sgid) + return true; +check_capable: + if (ns_capable(ns, CAP_SETGID)) + return true; + return false; +} + +static 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 +198,7 @@ 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
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