From patchwork Wed Aug 23 15:34:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13362779 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 5D0F7EE4993 for ; Wed, 23 Aug 2023 15:36:20 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qYpu5-0004VZ-Hg; Wed, 23 Aug 2023 11:36:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qYpsY-0001xS-DL for qemu-devel@nongnu.org; Wed, 23 Aug 2023 11:34:42 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qYpsW-000822-Ur for qemu-devel@nongnu.org; Wed, 23 Aug 2023 11:34:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692804879; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TwJjkgHsvXEBoKNEpyqvsbIlhmZVjsh0HgCHFDNzu50=; b=O+koEOwqsAnHLlL33cIOnTFYfc/8NyZFc7e3JI1RtKL8ExDzP7YzxB2Xd+EJP2V3T0+xmE sqSsjksigYLlrorx3HTnT4yleyrM5flC/TWnTLWgYYCehvsWakun/tGAV9UG3UMrP1+IrJ kESNMH642f89L3NW030Ci4R1epjD2Tk= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-275-EftSaAWGO7ueTBRapkvIIw-1; Wed, 23 Aug 2023 11:34:34 -0400 X-MC-Unique: EftSaAWGO7ueTBRapkvIIw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E690928040A7; Wed, 23 Aug 2023 15:34:33 +0000 (UTC) Received: from t14s.fritz.box (unknown [10.39.193.128]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2F1FA1121314; Wed, 23 Aug 2023 15:34:31 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Cc: qemu-ppc@nongnu.org, David Hildenbrand , Paolo Bonzini , Peter Xu , Igor Mammedov , Thiner Logoer , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , =?utf-8?q?Dani?= =?utf-8?q?el_P_=2E_Berrang=C3=A9?= , Stefan Hajnoczi , Elena Ufimtseva , Jagannathan Raman , "Michael S. Tsirkin" , Ani Sinha , Xiao Guangrong , Daniel Henrique Barboza , Greg Kurz , Eric Blake , Markus Armbruster , Eduardo Habkost Subject: [PATCH v3 06/11] softmmu/physmem: Fail creation of new files in file_ram_open() with readonly=true Date: Wed, 23 Aug 2023 17:34:06 +0200 Message-ID: <20230823153412.832081-7-david@redhat.com> In-Reply-To: <20230823153412.832081-1-david@redhat.com> References: <20230823153412.832081-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Currently, if a file does not exist yet, file_ram_open() will create new empty file and open it writable. However, it even does that when readonly=true was specified. Specifying O_RDONLY instead to create a new readonly file would theoretically work, however, ftruncate() will refuse to resize the new empty file and we'll get a warning: ftruncate: Invalid argument And later eventually more problems when actually mmap'ing that file and accessing it. If someone intends to let QEMU open+mmap a file read-only, better create+resize+fill that file ahead of time outside of QEMU context. We'll now fail with: ./qemu-system-x86_64 \ -object memory-backend-file,id=ram0,mem-path=tmp,readonly=true,size=1g qemu-system-x86_64: can't open backing store tmp for guest RAM: No such file or directory All use cases of readonly files (R/O NVDIMMs, VM templating) work on existing files, so silently creating new files might just hide user errors when accidentally specifying a non-existent file. Note that the only memory-backend-file will end up calling memory_region_init_ram_from_file() -> qemu_ram_alloc_from_file() -> file_ram_open(). Move error reporting to the single caller. Signed-off-by: David Hildenbrand Acked-by: Peter Xu --- softmmu/physmem.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/softmmu/physmem.c b/softmmu/physmem.c index 32d641754b..f8c47ecb85 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -1289,8 +1289,7 @@ static int64_t get_file_align(int fd) static int file_ram_open(const char *path, const char *region_name, bool readonly, - bool *created, - Error **errp) + bool *created) { char *filename; char *sanitized_name; @@ -1305,6 +1304,10 @@ static int file_ram_open(const char *path, break; } if (errno == ENOENT) { + if (readonly) { + /* Refuse to create new, readonly files. */ + return -ENOENT; + } /* @path names a file that doesn't exist, create it */ fd = open(path, O_RDWR | O_CREAT | O_EXCL, 0644); if (fd >= 0) { @@ -1334,10 +1337,7 @@ static int file_ram_open(const char *path, g_free(filename); } if (errno != EEXIST && errno != EINTR) { - error_setg_errno(errp, errno, - "can't open backing store %s for guest RAM", - path); - return -1; + return -errno; } /* * Try again on EINTR and EEXIST. The latter happens when @@ -1947,8 +1947,10 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, RAMBlock *block; fd = file_ram_open(mem_path, memory_region_name(mr), - !!(ram_flags & RAM_READONLY_FD), &created, errp); + !!(ram_flags & RAM_READONLY_FD), &created); if (fd < 0) { + error_setg_errno(errp, -fd, "can't open backing store %s for guest RAM", + mem_path); return NULL; }