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=-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=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 E41BEC433E1 for ; Mon, 24 Aug 2020 08:50:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B18612075B for ; Mon, 24 Aug 2020 08:50:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259059; bh=nstCH6mn71s6+t+b0/T4hwQQsqc+bqiv7+SPeqwEVLc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=vhh+ALofemE7i3R1/6gsQJbPdPO1zt/YBHUzLlR1BoNwcnY0Pu9gjhPihW82OLkVB nyeF4sFo5X06dBQMv51pGwuymH50JHL7E5fYb2fuWvQQHFbj2vQ7YtjvOKyOSybZwk 6R9wJ8EWZpz6HVL6cSzMP6GyerZIcjTY5U6ony4Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729879AbgHXIu6 (ORCPT ); Mon, 24 Aug 2020 04:50:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:54966 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728307AbgHXIus (ORCPT ); Mon, 24 Aug 2020 04:50:48 -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 5D837204FD; Mon, 24 Aug 2020 08:50:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259047; bh=nstCH6mn71s6+t+b0/T4hwQQsqc+bqiv7+SPeqwEVLc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IbAmazxZEmM2z3oDSQb2bvTeaiUdqTa+Wzghv+rNN4uSE6KmRY3zPZBM3FneR0pbO rUtQRWO62hduv4jvBePQJuoR/axGwGICSLGvXUo4+wFQE6i1wjFNpcrrVpu+BcoAyN hfek/5rHZ1ZqGkzUiTkH47nfYy31HLgBwKMp+LSA= 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 4.4 11/33] romfs: fix uninitialized memory leak in romfs_dev_read() Date: Mon, 24 Aug 2020 10:31:07 +0200 Message-Id: <20200824082347.084399389@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082346.498653578@linuxfoundation.org> References: <20200824082346.498653578@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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)