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,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 51725C52D3C for ; Thu, 27 Feb 2020 13:57:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1DB0D24656 for ; Thu, 27 Feb 2020 13:57:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582811875; bh=UHz6U+bje1bnx38zQBhWgN+LYj72XjeYmLgrKfw5bt0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=e7orEckUE+XmJFv5MnLKbvNVXj40x0ntoPJwW+0YzOK/raN7FVIF4o+tXWu/m00kV W1SIlwumUFIVu/bKiI0Ia02WPdKADlui9UaCQgTHGI97DW+m8wvGbWrpqIQIfvq2F7 hY0kJgwc5Puzo0Ny6srvJ20X4AIcfSXmo2Vwp1r0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732367AbgB0N5x (ORCPT ); Thu, 27 Feb 2020 08:57:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:58910 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732211AbgB0N5v (ORCPT ); Thu, 27 Feb 2020 08:57:51 -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 AE90B24691; Thu, 27 Feb 2020 13:57:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582811871; bh=UHz6U+bje1bnx38zQBhWgN+LYj72XjeYmLgrKfw5bt0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Std5Qpd6PSAQJpCgQiC8uF+CRDvT7kMmbC4FjUlOzd+wm5t/Yks2BhBdfXuy45Sw1 qdALH7cL1r71Uej47dQ7Jd6syw9gugnT+NpWPSw9yui62UInh2WtmEMwWJu622Ga6M CT7EE+/i7E89qLssqT+8DWBgOmA4Gph0uYrCWrDQ= 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 4.14 133/237] btrfs: safely advance counter when looking up bio csums Date: Thu, 27 Feb 2020 14:35:47 +0100 Message-Id: <20200227132306.503206704@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200227132255.285644406@linuxfoundation.org> References: <20200227132255.285644406@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: 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 702b3606ad0ec..717d82d51bb13 100644 --- a/fs/btrfs/file-item.c +++ b/fs/btrfs/file-item.c @@ -288,7 +288,8 @@ 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