From mboxrd@z Thu Jan 1 00:00:00 1970 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 B5C0EC2B9F4 for ; Tue, 22 Jun 2021 13:13:48 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 075436113E for ; Tue, 22 Jun 2021 13:13:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 075436113E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45794 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lvgDr-0004ml-0d for qemu-devel@archiver.kernel.org; Tue, 22 Jun 2021 09:13:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33590) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lveO8-0000vr-3l for qemu-devel@nongnu.org; Tue, 22 Jun 2021 07:16:16 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:2180) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lveNw-00008E-SA for qemu-devel@nongnu.org; Tue, 22 Jun 2021 07:16:09 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4G8NyB53Rwz71H0; Tue, 22 Jun 2021 19:11:46 +0800 (CST) Received: from dggema768-chm.china.huawei.com (10.1.198.210) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Tue, 22 Jun 2021 19:15:52 +0800 Received: from localhost (10.174.151.75) by dggema768-chm.china.huawei.com (10.1.198.210) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 22 Jun 2021 19:15:51 +0800 From: Lin Feng To: Subject: [PATCH] migration: fix the memory overwriting risk in add_to_iovec Date: Tue, 22 Jun 2021 19:15:49 +0800 Message-ID: <20210622111549.490-1-linfeng23@huawei.com> X-Mailer: git-send-email 2.30.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.174.151.75] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema768-chm.china.huawei.com (10.1.198.210) X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.189; envelope-from=linfeng23@huawei.com; helo=szxga03-in.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Tue, 22 Jun 2021 09:12:36 -0400 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: wangxinxin.wang@huawei.com, Feng Lin , dgilbert@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Feng Lin When testing migration, a Segmentation fault qemu core is generated. 0 error_free (err=0x1) 1 0x00007f8b862df647 in qemu_fclose (f=f@entry=0x55e06c247640) 2 0x00007f8b8516d59a in migrate_fd_cleanup (s=s@entry=0x55e06c0e1ef0) 3 0x00007f8b8516d66c in migrate_fd_cleanup_bh (opaque=0x55e06c0e1ef0) 4 0x00007f8b8626a47f in aio_bh_poll (ctx=ctx@entry=0x55e06b5a16d0) 5 0x00007f8b8626e71f in aio_dispatch (ctx=0x55e06b5a16d0) 6 0x00007f8b8626a33d in aio_ctx_dispatch (source=, callback=, user_data=) 7 0x00007f8b866bdba4 in g_main_context_dispatch () 8 0x00007f8b8626cde9 in glib_pollfds_poll () 9 0x00007f8b8626ce62 in os_host_main_loop_wait (timeout=) 10 0x00007f8b8626cffd in main_loop_wait (nonblocking=nonblocking@entry=0) 11 0x00007f8b862ef01f in main_loop () Using gdb print the struct QEMUFile f = { ..., iovcnt = 65, last_error = 21984, last_error_obj = 0x1, shutdown = true } Well iovcnt is overflow, because the max size of MAX_IOV_SIZE is 64. struct QEMUFile { ...; struct iovec iov[MAX_IOV_SIZE]; unsigned int iovcnt; int last_error; Error *last_error_obj; bool shutdown; }; iovcnt and last_error is overwrited by add_to_iovec(). Right now, add_to_iovec() increase iovcnt before check the limit. And it seems that add_to_iovec() assumes that iovcnt will set to zero in qemu_fflush(). But qemu_fflush() will directly return when f->shutdown is true. The situation may occur when libvirtd restart during migration, after f->shutdown is set, before calling qemu_file_set_error() in qemu_file_shutdown(). So the safiest way is checking the iovcnt before increasing it. Signed-off-by: Feng Lin --- migration/qemu-file.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/migration/qemu-file.c b/migration/qemu-file.c index d6e03dbc0e..3dde1a193c 100644 --- a/migration/qemu-file.c +++ b/migration/qemu-file.c @@ -419,8 +419,10 @@ static int add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size, if (may_free) { set_bit(f->iovcnt, f->may_free); } - f->iov[f->iovcnt].iov_base = (uint8_t *)buf; - f->iov[f->iovcnt++].iov_len = size; + if (f->iovcnt < MAX_IOV_SIZE) { + f->iov[f->iovcnt].iov_base = (uint8_t *)buf; + f->iov[f->iovcnt++].iov_len = size; + } } if (f->iovcnt >= MAX_IOV_SIZE) { -- 2.23.0