From patchwork Mon Aug 24 08:31:01 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 265092 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=-10.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 D58C1C433DF for ; Mon, 24 Aug 2020 09:22:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B60CD2074D for ; Mon, 24 Aug 2020 09:22:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598260950; bh=nstCH6mn71s6+t+b0/T4hwQQsqc+bqiv7+SPeqwEVLc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yFyrRHYR5UgpE8ROFSDMuG7gc8OFSYw5Li8DFObPPYxONn1oyKbLCg1Nu70pOK63u 8y6aRq/BBb3NmI+m2U0NnqSP7yKoAame1coRP7huYNESIPpdPr1K0U6Ej7yd5iswLC ei2hMz4exJzt7dIbvaYn/YNzf6i1WmVm6A/19dFA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728972AbgHXJWP (ORCPT ); Mon, 24 Aug 2020 05:22:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:36760 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730395AbgHXIzK (ORCPT ); Mon, 24 Aug 2020 04:55:10 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 32AF2204FD; Mon, 24 Aug 2020 08:55:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259309; bh=nstCH6mn71s6+t+b0/T4hwQQsqc+bqiv7+SPeqwEVLc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FbbM0E47TJ1z24JO9GWb5IJCWFXsdlDsp+DQcH7XqACugfJ1nXvAWHea14Rq/mqOr 1Q0BdH+CuSCTEb0TGZB7apZ+TLClp9vK1A0qn2oH0tCNuOIYWTKF21xt2ENufBCarh rBV30cJD+cMUlY2+SIGtGSzVJB+PS6MnZRpk5f7U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Andrew Morton , David Howells , Linus Torvalds Subject: [PATCH 4.19 10/71] romfs: fix uninitialized memory leak in romfs_dev_read() Date: Mon, 24 Aug 2020 10:31:01 +0200 Message-Id: <20200824082356.398552400@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082355.848475917@linuxfoundation.org> References: <20200824082355.848475917@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jann Horn commit bcf85fcedfdd17911982a3e3564fcfec7b01eebd upstream. romfs has a superblock field that limits the size of the filesystem; data beyond that limit is never accessed. romfs_dev_read() fetches a caller-supplied number of bytes from the backing device. It returns 0 on success or an error code on failure; therefore, its API can't represent short reads, it's all-or-nothing. However, when romfs_dev_read() detects that the requested operation would cross the filesystem size limit, it currently silently truncates the requested number of bytes. This e.g. means that when the content of a file with size 0x1000 starts one byte before the filesystem size limit, ->readpage() will only fill a single byte of the supplied page while leaving the rest uninitialized, leaking that uninitialized memory to userspace. Fix it by returning an error code instead of truncating the read when the requested read operation would go beyond the end of the filesystem. Fixes: da4458bda237 ("NOMMU: Make it possible for RomFS to use MTD devices directly") Signed-off-by: Jann Horn Signed-off-by: Andrew Morton Reviewed-by: Greg Kroah-Hartman Cc: David Howells Cc: Link: http://lkml.kernel.org/r/20200818013202.2246365-1-jannh@google.com Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/romfs/storage.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/fs/romfs/storage.c +++ b/fs/romfs/storage.c @@ -221,10 +221,8 @@ int romfs_dev_read(struct super_block *s size_t limit; limit = romfs_maxsize(sb); - if (pos >= limit) + if (pos >= limit || buflen > limit - pos) return -EIO; - if (buflen > limit - pos) - buflen = limit - pos; #ifdef CONFIG_ROMFS_ON_MTD if (sb->s_mtd)