From patchwork Fri Jun 8 20:31:46 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Scott Mayhew X-Patchwork-Id: 10455221 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 86A9760159 for ; Fri, 8 Jun 2018 20:31:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8443929557 for ; Fri, 8 Jun 2018 20:31:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 78785295A6; Fri, 8 Jun 2018 20:31:49 +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,HEXHASH_WORD, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham 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 E6B7D29557 for ; Fri, 8 Jun 2018 20:31:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752952AbeFHUbs (ORCPT ); Fri, 8 Jun 2018 16:31:48 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:46468 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752904AbeFHUbr (ORCPT ); Fri, 8 Jun 2018 16:31:47 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 26C41818BAFC; Fri, 8 Jun 2018 20:31:47 +0000 (UTC) Received: from coeurl.usersys.redhat.com (ovpn-123-205.rdu2.redhat.com [10.10.123.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id F31A12166BB2; Fri, 8 Jun 2018 20:31:46 +0000 (UTC) Received: by coeurl.usersys.redhat.com (Postfix, from userid 1000) id A18CB2042F; Fri, 8 Jun 2018 16:31:46 -0400 (EDT) From: Scott Mayhew To: bfields@fieldses.org, jlayton@kernel.org Cc: linux-nfs@vger.kernel.org Subject: [PATCH] nfsd: fix potential use-after-free in nfsd4_decode_getdeviceinfo Date: Fri, 8 Jun 2018 16:31:46 -0400 Message-Id: <20180608203146.19810-1-smayhew@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Fri, 08 Jun 2018 20:31:47 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Fri, 08 Jun 2018 20:31:47 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'smayhew@redhat.com' RCPT:'' Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When running a fuzz tester against a KASAN-enabled kernel, the following splat periodically occurs. The problem occurs when the test sends a GETDEVICEINFO request with a malformed xdr array (size but no data) for gdia_notify_types and the array size is > 0x3fffffff, which results in an overflow in the value of nbytes which is passed to read_buf(). If the array size is 0x40000000, 0x80000000, or 0xc0000000, then after the overflow occurs, the value of nbytes 0, and when that happens the pointer returned by read_buf() points to the end of the xdr data (i.e. argp->end) when really it should be returning NULL. Fix this by returning NFS4ERR_BAD_XDR if the array size is > 1000 (this value is arbitrary, but it's the same threshold used by nfsd4_decode_bitmap()... in could really be any value >= 1 since it's expected to get at most a single bitmap in gdia_notify_types). [ 119.256854] ================================================================== [ 119.257611] BUG: KASAN: use-after-free in nfsd4_decode_getdeviceinfo+0x5a4/0x5b0 [nfsd] [ 119.258422] Read of size 4 at addr ffff880113ada000 by task nfsd/538 [ 119.259146] CPU: 0 PID: 538 Comm: nfsd Not tainted 4.17.0+ #1 [ 119.259662] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014 [ 119.261202] Call Trace: [ 119.262265] dump_stack+0x71/0xab [ 119.263371] print_address_description+0x6a/0x270 [ 119.264609] kasan_report+0x258/0x380 [ 119.265854] ? nfsd4_decode_getdeviceinfo+0x5a4/0x5b0 [nfsd] [ 119.267291] nfsd4_decode_getdeviceinfo+0x5a4/0x5b0 [nfsd] [ 119.268549] ? nfs4svc_decode_compoundargs+0xa5b/0x13c0 [nfsd] [ 119.269873] ? nfsd4_decode_sequence+0x490/0x490 [nfsd] [ 119.271095] nfs4svc_decode_compoundargs+0xa5b/0x13c0 [nfsd] [ 119.272393] ? nfsd4_release_compoundargs+0x1b0/0x1b0 [nfsd] [ 119.273658] nfsd_dispatch+0x183/0x850 [nfsd] [ 119.274918] svc_process+0x161c/0x31a0 [sunrpc] [ 119.276172] ? svc_printk+0x190/0x190 [sunrpc] [ 119.277386] ? svc_xprt_release+0x451/0x680 [sunrpc] [ 119.278622] nfsd+0x2b9/0x430 [nfsd] [ 119.279771] ? nfsd_destroy+0x1c0/0x1c0 [nfsd] [ 119.281157] kthread+0x2db/0x390 [ 119.282347] ? kthread_create_worker_on_cpu+0xc0/0xc0 [ 119.283756] ret_from_fork+0x35/0x40 [ 119.286041] Allocated by task 436: [ 119.287525] kasan_kmalloc+0xa0/0xd0 [ 119.288685] kmem_cache_alloc+0xe9/0x1f0 [ 119.289900] get_empty_filp+0x7b/0x410 [ 119.291037] path_openat+0xca/0x4220 [ 119.292242] do_filp_open+0x182/0x280 [ 119.293411] do_sys_open+0x216/0x360 [ 119.294555] do_syscall_64+0xa0/0x2f0 [ 119.295721] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 119.298068] Freed by task 436: [ 119.299271] __kasan_slab_free+0x130/0x180 [ 119.300557] kmem_cache_free+0x78/0x210 [ 119.301823] rcu_process_callbacks+0x35b/0xbd0 [ 119.303162] __do_softirq+0x192/0x5ea [ 119.305443] The buggy address belongs to the object at ffff880113ada000 which belongs to the cache filp of size 256 [ 119.308556] The buggy address is located 0 bytes inside of 256-byte region [ffff880113ada000, ffff880113ada100) [ 119.311376] The buggy address belongs to the page: [ 119.312728] page:ffffea00044eb680 count:1 mapcount:0 mapping:0000000000000000 index:0xffff880113ada780 [ 119.314428] flags: 0x17ffe000000100(slab) [ 119.315740] raw: 0017ffe000000100 0000000000000000 ffff880113ada780 00000001000c0001 [ 119.317379] raw: ffffea0004553c60 ffffea00045c11e0 ffff88011b167e00 0000000000000000 [ 119.319050] page dumped because: kasan: bad access detected [ 119.321652] Memory state around the buggy address: [ 119.322993] ffff880113ad9f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 119.324515] ffff880113ad9f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 119.326087] >ffff880113ada000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 119.327547] ^ [ 119.328730] ffff880113ada080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 119.330218] ffff880113ada100: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb [ 119.331740] ================================================================== Signed-off-by: Scott Mayhew --- fs/nfsd/nfs4xdr.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 1d048dd..48e412e 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -1585,6 +1585,8 @@ nfsd4_decode_getdeviceinfo(struct nfsd4_compoundargs *argp, gdev->gd_maxcount = be32_to_cpup(p++); num = be32_to_cpup(p++); if (num) { + if (num > 1000) + goto xdr_error; READ_BUF(4 * num); gdev->gd_notify_types = be32_to_cpup(p++); for (i = 1; i < num; i++) {