From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1105E606A336 for ; Tue, 10 Nov 2026 15:12:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=MkHxNIPQ Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xQnVZ-00078Y-Ct; Tue, 10 Nov 2026 10:11:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xQnVW-00078A-VB for qemu-devel@nongnu.org; Tue, 10 Nov 2026 10:11:35 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xQnVV-0001HT-DZ for qemu-devel@nongnu.org; Tue, 10 Nov 2026 10:11:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1794323491; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XKImayUcNvzNj599xfEmYeVHESZuNlvvUEQZInPdB64=; b=MkHxNIPQ2DhfO2g/8qlJVJ0FD/e52U7WzR7kfWscTSKw/EK6AIodR2+HFtYWYDsSXFVYZT rqYAQS8vS0ASFNwGI2aNuXk2OuMHuWhMg3jwOPaFUghLdhjYBcmHrUvE5i+RM4Ah6RYauf 8s0ZzfQDgf9NGjouBm6kulV06N3Fvmg= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-400-72e7_HSLMc-v84zRpGtK2g-1; Tue, 10 Nov 2026 10:11:28 -0500 X-MC-Unique: 72e7_HSLMc-v84zRpGtK2g-1 X-Mimecast-MFC-AGG-ID: 72e7_HSLMc-v84zRpGtK2g_1794323487 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A26F619560A2; Tue, 10 Nov 2026 15:11:26 +0000 (UTC) Received: from redhat.com (unknown [10.44.48.125]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E738930030FB; Tue, 10 Nov 2026 15:11:24 +0000 (UTC) Date: Tue, 10 Nov 2026 16:11:22 +0100 From: Kevin Wolf To: malike Cc: qemu-devel@nongnu.org, stefanha@redhat.com, hreitz@redhat.com Subject: Re: [PATCH] block/bochs: validate bitmap size and compute extent_blocks after validation Message-ID: References: <20261014033419.236057-1-malike@kylinos.cn> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261014033419.236057-1-malike@kylinos.cn> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 5 X-Spam_score: 0.5 X-Spam_bar: / X-Spam_report: (0.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Am 14.10.2026 um 05:34 hat malike geschrieben: > bochs_open() computes bitmap_blocks using the formula > "1 + (le32_to_cpu(bochs.bitmap) - 1) / 512". le32_to_cpu() returns > uint32_t, so when bochs.bitmap is zero the subtraction wraps to > UINT32_MAX (0xFFFFFFFF) in unsigned arithmetic, yielding > bitmap_blocks = 8388608 instead of 1. > > The bitmap field is read directly from the on-disk image header and was > never validated. The overflowed bitmap_blocks propagates into > seek_to_sector()'s bitmap_offset calculation, causing reads to target > wrong offsets and return I/O errors or incorrect data. > > Add an explicit zero check for bochs.bitmap before the formula. > > Also move the extent_blocks calculation to after the existing > extent_size validation. The same "1 + (x - 1) / 512" pattern applies > to extent, but extent==0 is already caught by the "extent_size < > BDRV_SECTOR_SIZE" check; the calculation is moved after that check for > clarity and robustness, and uses the already-validated s->extent_size > instead of re-reading the header field. > > Fixes: a8753c3466dc ("Bochs disk image support") > Signed-off-by: malike Thanks, applied to the block branch. Of course, this alone isn't enough to fully validate the bitmap size. Instead of incorrectly wrapping for a zero size bitmap and getting a too large number from this, the header field could directly specify an incorrect number that would have the same result in seek_to_sector(). qemu-iotests 078 could be extended to check different values for the bitmap size, too, to catch these cases. Kevin