From: Eric W. Biederman <ebiederm@xmission.com>
Date: Thu, 17 Nov 2016 07:38:35 +0000 (-0600)
Subject: exec: Don't reset euid and egid when the tracee has CAP_SETUID
X-Git-Tag: v4.14-rc1~1421^2~13
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=70169420f555210147f3cab74bb0f6debd488bdb;p=platform%2Fkernel%2Flinux-rpi.git

exec: Don't reset euid and egid when the tracee has CAP_SETUID

Don't reset euid and egid when the tracee has CAP_SETUID in
it's user namespace.  I punted on relaxing this permission check
long ago but now that I have read this code closely it is clear
it is safe to test against CAP_SETUID in the user namespace.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---

diff --git a/security/commoncap.c b/security/commoncap.c
index 8df676f..feb6044 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -550,7 +550,7 @@ skip:
 	     !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
 	    bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
 		/* downgrade; they get no more than they had, and maybe less */
-		if (!capable(CAP_SETUID) ||
+		if (!ns_capable(new->user_ns, CAP_SETUID) ||
 		    (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
 			new->euid = new->uid;
 			new->egid = new->gid;