From patchwork Wed Oct 26 14:01:54 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 9397347 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8990560231 for ; Wed, 26 Oct 2016 14:03:20 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6404629BB6 for ; Wed, 26 Oct 2016 14:03:20 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5890929BCB; Wed, 26 Oct 2016 14:03:20 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0160629BB6 for ; Wed, 26 Oct 2016 14:03:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757833AbcJZOCx (ORCPT ); Wed, 26 Oct 2016 10:02:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47434 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755505AbcJZOCv (ORCPT ); Wed, 26 Oct 2016 10:02:51 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D539261BAF; Wed, 26 Oct 2016 14:01:56 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-116-17.phx2.redhat.com [10.3.116.17]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u9QE1sVM009763; Wed, 26 Oct 2016 10:01:55 -0400 Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 1/3] KEYS: Fix short sprintf buffer in /proc/keys show function From: David Howells To: jmorris@namei.org Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, Ondrej Kozina Date: Wed, 26 Oct 2016 15:01:54 +0100 Message-ID: <147749051466.683.1468192388049457663.stgit@warthog.procyon.org.uk> In-Reply-To: <147749050748.683.4024891882293453809.stgit@warthog.procyon.org.uk> References: <147749050748.683.4024891882293453809.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 26 Oct 2016 14:01:57 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP This fixes CVE-2016-7042. Fix a short sprintf buffer in proc_keys_show(). If the gcc stack protector is turned on, this can cause a panic due to stack corruption. The problem is that xbuf[] is not big enough to hold a 64-bit timeout rendered as weeks: (gdb) p 0xffffffffffffffffULL/(60*60*24*7) $2 = 30500568904943 That's 14 chars plus NUL, not 11 chars plus NUL. Expand the buffer to 16 chars. I think the unpatched code apparently works if the stack-protector is not enabled because on a 32-bit machine the buffer won't be overflowed and on a 64-bit machine there's a 64-bit aligned pointer at one side and an int that isn't checked again on the other side. The panic incurred looks something like: Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81352ebe CPU: 0 PID: 1692 Comm: reproducer Not tainted 4.7.2-201.fc24.x86_64 #1 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 0000000000000086 00000000fbbd2679 ffff8800a044bc00 ffffffff813d941f ffffffff81a28d58 ffff8800a044bc98 ffff8800a044bc88 ffffffff811b2cb6 ffff880000000010 ffff8800a044bc98 ffff8800a044bc30 00000000fbbd2679 Call Trace: [] dump_stack+0x63/0x84 [] panic+0xde/0x22a [] ? proc_keys_show+0x3ce/0x3d0 [] __stack_chk_fail+0x19/0x30 [] proc_keys_show+0x3ce/0x3d0 [] ? key_validate+0x50/0x50 [] ? key_default_cmp+0x20/0x20 [] seq_read+0x2cc/0x390 [] proc_reg_read+0x42/0x70 [] __vfs_read+0x37/0x150 [] ? security_file_permission+0xa0/0xc0 [] vfs_read+0x96/0x130 [] SyS_read+0x55/0xc0 [] entry_SYSCALL_64_fastpath+0x1a/0xa4 Reported-by: Ondrej Kozina Signed-off-by: David Howells Tested-by: Ondrej Kozina cc: stable@vger.kernel.org --- security/keys/proc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/security/keys/proc.c b/security/keys/proc.c index f0611a6368cd..b9f531c9e4fa 100644 --- a/security/keys/proc.c +++ b/security/keys/proc.c @@ -181,7 +181,7 @@ static int proc_keys_show(struct seq_file *m, void *v) struct timespec now; unsigned long timo; key_ref_t key_ref, skey_ref; - char xbuf[12]; + char xbuf[16]; int rc; struct keyring_search_context ctx = {