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Subject[RFC PATCH 10/14] net/core/scm.c: target capable() calls to user_ns owning the net_ns
Date
From: Serge E. Hallyn <serge.hallyn@canonical.com>

The uid/gid comparisons don't have to be pulled out. This just seemed
more easily proved correct.

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---
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 4c1ef02..21b5d0b 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(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(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;

--
1.7.4.1


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