From patchwork Mon Jun 1 17:53:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 224850 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9EF3C433E1 for ; Mon, 1 Jun 2020 19:01:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 80D1A206E2 for ; Mon, 1 Jun 2020 19:01:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591038063; bh=v5U3mBbn3YdGBHEeSmql6qdA7BvIvIIiq7B/D57Y0Qk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0+jTo0DpMAis3PPAcaG02D+R1I6clSs3Y5XhOBLW4M14tUV3y8kN0Y/43Ig5HKtl4 v+86eqxiCt2v42oJnJ3AIcNCFR8mj6P5KA8RB8rdS/1pnZxnawMIX9AOniGgoAsdQO mXfXZrnWLjEGTlHipaF1tGSJyf/KjBILVefDS8mU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728495AbgFAR4I (ORCPT ); Mon, 1 Jun 2020 13:56:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:36292 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728480AbgFAR4H (ORCPT ); Mon, 1 Jun 2020 13:56:07 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 65AAC2073B; Mon, 1 Jun 2020 17:56:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591034166; bh=v5U3mBbn3YdGBHEeSmql6qdA7BvIvIIiq7B/D57Y0Qk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0ve9FbZnY8lJhPm+KuyCmj9rQzfJjVVAmLvkscZX1SuIJnX4miQiaT0BvxIacO53H vDxAy01NFgKhLRxFGAbKS6wLdwznePsw6z7Lu0ddgQ7lDdkuDBojCDo8iPiNUa9Dia mUtmJJscbIB+J+uLXUo05U3W29tFIt3E4AMtfkJc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , "Eric W. Biederman" , Sasha Levin Subject: [PATCH 4.4 21/48] exec: Always set cap_ambient in cap_bprm_set_creds Date: Mon, 1 Jun 2020 19:53:31 +0200 Message-Id: <20200601173958.705938704@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200601173952.175939894@linuxfoundation.org> References: <20200601173952.175939894@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric W. Biederman [ Upstream commit a4ae32c71fe90794127b32d26d7ad795813b502e ] An invariant of cap_bprm_set_creds is that every field in the new cred structure that cap_bprm_set_creds might set, needs to be set every time to ensure the fields does not get a stale value. The field cap_ambient is not set every time cap_bprm_set_creds is called, which means that if there is a suid or sgid script with an interpreter that has neither the suid nor the sgid bits set the interpreter should be able to accept ambient credentials. Unfortuantely because cap_ambient is not reset to it's original value the interpreter can not accept ambient credentials. Given that the ambient capability set is expected to be controlled by the caller, I don't think this is particularly serious. But it is definitely worth fixing so the code works correctly. I have tested to verify my reading of the code is correct and the interpreter of a sgid can receive ambient capabilities with this change and cannot receive ambient capabilities without this change. Cc: stable@vger.kernel.org Cc: Andy Lutomirski Fixes: 58319057b784 ("capabilities: ambient capabilities") Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin --- security/commoncap.c | 1 + 1 file changed, 1 insertion(+) diff --git a/security/commoncap.c b/security/commoncap.c index 48071ed7c445..b62f97d83fd8 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -494,6 +494,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) int ret; kuid_t root_uid; + new->cap_ambient = old->cap_ambient; if (WARN_ON(!cap_ambient_invariant_ok(old))) return -EPERM;