From patchwork Tue Nov 7 22:29:02 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 10047323 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 233CB60360 for ; Tue, 7 Nov 2017 22:29:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 151C228D31 for ; Tue, 7 Nov 2017 22:29:23 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 09E6429C6C; Tue, 7 Nov 2017 22:29:23 +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 A22FF28D31 for ; Tue, 7 Nov 2017 22:29:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933749AbdKGW3I (ORCPT ); Tue, 7 Nov 2017 17:29:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38490 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932583AbdKGW3H (ORCPT ); Tue, 7 Nov 2017 17:29:07 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AE709C03BD52; Tue, 7 Nov 2017 22:29:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com AE709C03BD52 Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=dhowells@redhat.com Received: from warthog.procyon.org.uk.com (ovpn-121-14.rdu2.redhat.com [10.10.121.14]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3237B5D9CD; Tue, 7 Nov 2017 22:29:04 +0000 (UTC) From: David Howells To: jmorris@namei.org Cc: dhowells@redhat.com, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Eric Biggers Subject: [PATCH] KEYS: fix NULL pointer dereference during ASN.1 parsing [ver #2] Date: Tue, 7 Nov 2017 22:29:02 +0000 Message-Id: <151009374279.30629.14262211006816238165.stgit@warthog.procyon.org.uk> Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Tue, 07 Nov 2017 22:29:07 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers syzkaller reported a NULL pointer dereference in asn1_ber_decoder(). It can be reproduced by the following command, assuming CONFIG_PKCS7_TEST_KEY=y: keyctl add pkcs7_test desc '' @s The bug is that if the data buffer is empty, an integer underflow occurs in the following check: if (unlikely(dp >= datalen - 1)) goto data_overrun_error; This results in the NULL data pointer being dereferenced. Fix it by checking for 'datalen - dp < 2' instead. Also fix the similar check for 'dp >= datalen - n' later in the same function. That one possibly could result in a buffer overread. The NULL pointer dereference was reproducible using the "pkcs7_test" key type but not the "asymmetric" key type because the "asymmetric" key type checks for a 0-length payload before calling into the ASN.1 decoder but the "pkcs7_test" key type does not. The bug report was: BUG: unable to handle kernel NULL pointer dereference at (null) IP: asn1_ber_decoder+0x17f/0xe60 lib/asn1_decoder.c:233 PGD 7b708067 P4D 7b708067 PUD 7b6ee067 PMD 0 Oops: 0000 [#1] SMP Modules linked in: CPU: 0 PID: 522 Comm: syz-executor1 Not tainted 4.14.0-rc8 #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.3-20171021_125229-anatol 04/01/2014 task: ffff9b6b3798c040 task.stack: ffff9b6b37970000 RIP: 0010:asn1_ber_decoder+0x17f/0xe60 lib/asn1_decoder.c:233 RSP: 0018:ffff9b6b37973c78 EFLAGS: 00010216 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000021c RDX: ffffffff814a04ed RSI: ffffb1524066e000 RDI: ffffffff910759e0 RBP: ffff9b6b37973d60 R08: 0000000000000001 R09: ffff9b6b3caa4180 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f10ed1f2700(0000) GS:ffff9b6b3ea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000007b6f3000 CR4: 00000000000006f0 Call Trace: pkcs7_parse_message+0xee/0x240 crypto/asymmetric_keys/pkcs7_parser.c:139 verify_pkcs7_signature+0x33/0x180 certs/system_keyring.c:216 pkcs7_preparse+0x41/0x70 crypto/asymmetric_keys/pkcs7_key_type.c:63 key_create_or_update+0x180/0x530 security/keys/key.c:855 SYSC_add_key security/keys/keyctl.c:122 [inline] SyS_add_key+0xbf/0x250 security/keys/keyctl.c:62 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x4585c9 RSP: 002b:00007f10ed1f1bd8 EFLAGS: 00000216 ORIG_RAX: 00000000000000f8 RAX: ffffffffffffffda RBX: 00007f10ed1f2700 RCX: 00000000004585c9 RDX: 0000000020000000 RSI: 0000000020008ffb RDI: 0000000020008000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000216 R12: 00007fff1b2260ae R13: 00007fff1b2260af R14: 00007f10ed1f2700 R15: 0000000000000000 Code: dd ca ff 48 8b 45 88 48 83 e8 01 4c 39 f0 0f 86 a8 07 00 00 e8 53 dd ca ff 49 8d 46 01 48 89 85 58 ff ff ff 48 8b 85 60 ff ff ff <42> 0f b6 0c 30 89 c8 88 8d 75 ff ff ff 83 e0 1f 89 8d 28 ff ff RIP: asn1_ber_decoder+0x17f/0xe60 lib/asn1_decoder.c:233 RSP: ffff9b6b37973c78 CR2: 0000000000000000 Fixes: 42d5ec27f873 ("X.509: Add an ASN.1 decoder") Reported-by: syzbot Cc: # v3.7+ Signed-off-by: Eric Biggers Signed-off-by: David Howells --- lib/asn1_decoder.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 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/lib/asn1_decoder.c b/lib/asn1_decoder.c index fef5d2e114be..1ef0cec38d78 100644 --- a/lib/asn1_decoder.c +++ b/lib/asn1_decoder.c @@ -228,7 +228,7 @@ int asn1_ber_decoder(const struct asn1_decoder *decoder, hdr = 2; /* Extract a tag from the data */ - if (unlikely(dp >= datalen - 1)) + if (unlikely(datalen - dp < 2)) goto data_overrun_error; tag = data[dp++]; if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) @@ -274,7 +274,7 @@ int asn1_ber_decoder(const struct asn1_decoder *decoder, int n = len - 0x80; if (unlikely(n > 2)) goto length_too_long; - if (unlikely(dp >= datalen - n)) + if (unlikely(n > datalen - dp)) goto data_overrun_error; hdr += n; for (len = 0; n > 0; n--) {