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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 CDD9EC35645 for ; Fri, 21 Feb 2020 08:41:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B0B2206DB for ; Fri, 21 Feb 2020 08:41:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582274496; bh=nVj7nRN/y57cRavWIX1nbC+647lSGkrubQeT0m+Ut4M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=b2OBTbfucWFVDIzdeYZ/SGpfWqZRNYKTI7Xu99UGhR5GZDCyzE//zzp/8f+bQjE+J vLoWLeKFtaaJFiC3iL5SNzIgyEUaavD7isc3rxZIUVkvoZTi1wmFs0wPqCzgD1urst Q1pB97j6TUY5oZJMI5pVRn/Ju/EYFwvbt2xNz5eg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730677AbgBUIlf (ORCPT ); Fri, 21 Feb 2020 03:41:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:56420 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730389AbgBUH44 (ORCPT ); Fri, 21 Feb 2020 02:56:56 -0500 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 0696720578; Fri, 21 Feb 2020 07:56:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582271816; bh=nVj7nRN/y57cRavWIX1nbC+647lSGkrubQeT0m+Ut4M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eMQK2vRvkuY5E/n6h25SYFNIV8qeEynnZwA/jFEw5maTslAl/o0vgOMzskm3p91ZN F4kCbLpM9qYyATKQoi+M2cJeksjuCHExUigMmCHTH3hfTzN7PVlCuz6ir5Kx3g4sJC it85Do3welgxc7AW5i0kmnXVZHFwK0ndTbNaP1uU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Carpenter , Josef Bacik , David Sterba , Sasha Levin Subject: [PATCH 5.5 308/399] btrfs: safely advance counter when looking up bio csums Date: Fri, 21 Feb 2020 08:40:33 +0100 Message-Id: <20200221072431.530297023@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200221072402.315346745@linuxfoundation.org> References: <20200221072402.315346745@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: David Sterba [ Upstream commit 4babad10198fa73fe73239d02c2e99e3333f5f5c ] Dan's smatch tool reports fs/btrfs/file-item.c:295 btrfs_lookup_bio_sums() warn: should this be 'count == -1' which points to the while (count--) loop. With count == 0 the check itself could decrement it to -1. There's a WARN_ON a few lines below that has never been seen in practice though. It turns out that the value of page_bytes_left matches the count (by sectorsize multiples). The loop never reaches the state where count would go to -1, because page_bytes_left == 0 is found first and this breaks out. For clarity, use only plain check on count (and only for positive value), decrement safely inside the loop. Any other discrepancy after the whole bio list processing should be reported by the exising WARN_ON_ONCE as well. Reported-by: Dan Carpenter Reviewed-by: Josef Bacik Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/file-item.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c index b1bfdc5c1387a..6f18333e83c33 100644 --- a/fs/btrfs/file-item.c +++ b/fs/btrfs/file-item.c @@ -274,7 +274,8 @@ found: csum += count * csum_size; nblocks -= count; next: - while (count--) { + while (count > 0) { + count--; disk_bytenr += fs_info->sectorsize; offset += fs_info->sectorsize; page_bytes_left -= fs_info->sectorsize; -- 2.20.1