userns: user namespaces: convert several capable() calls

CAP_IPC_OWNER and CAP_IPC_LOCK can be checked against current_user_ns(),
because the resource comes from current's own ipc namespace.

setuid/setgid are to uids in own namespace, so again checks can be against
current_user_ns().

Changelog:
	Jan 11: Use task_ns_capable() in place of sched_capable().
	Jan 11: Use nsown_capable() as suggested by Bastian Blank.
	Jan 11: Clarify (hopefully) some logic in futex and sched.c
	Feb 15: use ns_capable for ipc, not nsown_capable
	Feb 23: let copy_ipcs handle setting ipc_ns->user_ns
	Feb 23: pass ns down rather than taking it from current

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index bda415715382..6570c459f31c 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2418,10 +2418,19 @@ SYSCALL_DEFINE3(get_robust_list, int, pid,
                         goto err_unlock;
                 ret = -EPERM;
                 pcred = __task_cred(p);
+                /* If victim is in different user_ns, then uids are not
+                   comparable, so we must have CAP_SYS_PTRACE */
+                if (cred->user->user_ns != pcred->user->user_ns) {
+                        if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
+                                goto err_unlock;
+                        goto ok;
+                }
+                /* If victim is in same user_ns, then uids are comparable */
                 if (cred->euid != pcred->euid &&
                     cred->euid != pcred->uid &&
-                    !capable(CAP_SYS_PTRACE))
+                    !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
                         goto err_unlock;
+ok:
                 head = p->robust_list;
                 rcu_read_unlock();
         }