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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB2B6C43334 for ; Mon, 13 Jun 2022 12:01:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358178AbiFMMBz (ORCPT ); Mon, 13 Jun 2022 08:01:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358126AbiFML7c (ORCPT ); Mon, 13 Jun 2022 07:59:32 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DEBAB4E3A8; Mon, 13 Jun 2022 03:56:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F3BA861257; Mon, 13 Jun 2022 10:56:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D0CEC36B00; Mon, 13 Jun 2022 10:56:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655117788; bh=Ir1rYjo3alo8qSTxL/ehnAekfnmDw3mCZWfS6ECO2Ks=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0F0CiGK+8l4UWRjRC8TQmeCx8E2Bg/Hlh+TEuu56Aq/IXvC67ab465tF6DFF/eaFI 2I+VWDXPWfMPQ0WyPeBWkzNT4Hgbgp5QFJhrBJadISaIrz2ZTiyHOiv8v2W9dTyBZP y4KDXTrgBSPYMX5l7X7P8kTbhx31STRUktESNf+k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jakob Koschel , Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 4.19 132/287] f2fs: fix dereference of stale list iterator after loop body Date: Mon, 13 Jun 2022 12:09:16 +0200 Message-Id: <20220613094927.881449853@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094923.832156175@linuxfoundation.org> References: <20220613094923.832156175@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jakob Koschel [ Upstream commit 2aaf51dd39afb6d01d13f1e6fe20b684733b37d5 ] The list iterator variable will be a bogus pointer if no break was hit. Dereferencing it (cur->page in this case) could load an out-of-bounds/undefined value making it unsafe to use that in the comparision to determine if the specific element was found. Since 'cur->page' *can* be out-ouf-bounds it cannot be guaranteed that by chance (or intention of an attacker) it matches the value of 'page' even though the correct element was not found. This is fixed by using a separate list iterator variable for the loop and only setting the original variable if a suitable element was found. Then determing if the element was found is simply checking if the variable is set. Fixes: 8c242db9b8c0 ("f2fs: fix stale ATOMIC_WRITTEN_PAGE private pointer") Signed-off-by: Jakob Koschel Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin --- fs/f2fs/segment.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 0e3e590a250f..6fbf0471323e 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -354,16 +354,19 @@ void f2fs_drop_inmem_page(struct inode *inode, struct page *page) struct f2fs_sb_info *sbi = F2FS_I_SB(inode); struct list_head *head = &fi->inmem_pages; struct inmem_pages *cur = NULL; + struct inmem_pages *tmp; f2fs_bug_on(sbi, !IS_ATOMIC_WRITTEN_PAGE(page)); mutex_lock(&fi->inmem_lock); - list_for_each_entry(cur, head, list) { - if (cur->page == page) + list_for_each_entry(tmp, head, list) { + if (tmp->page == page) { + cur = tmp; break; + } } - f2fs_bug_on(sbi, list_empty(head) || cur->page != page); + f2fs_bug_on(sbi, !cur); list_del(&cur->list); mutex_unlock(&fi->inmem_lock); -- 2.35.1