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=-13.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 37861C43387 for ; Tue, 8 Jan 2019 19:34:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F17B420827 for ; Tue, 8 Jan 2019 19:34:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546976055; bh=I6sIGRbLxUoN5H26RkCyWXo10trpRo76osjr4rXjLag=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2tmsjHww7Gh9/S4UTR70jL7PPl/Rxw+30Wo29lqkEpHT36HiINtXsqfjD2Uhvlk6H 4DF4kVxIyCO6IpM7zLzLXtQXEBdzDIGyDHAkrtXDQ8xcGZ5EEMegNYptoyFgTTBZGr 4GMIoyyJIpybf27dg20jsB+loTMqeBNmBc7BNXOY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731917AbfAHTeO (ORCPT ); Tue, 8 Jan 2019 14:34:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:42896 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731894AbfAHTeK (ORCPT ); Tue, 8 Jan 2019 14:34:10 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CCE842063F; Tue, 8 Jan 2019 19:34:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546976049; bh=I6sIGRbLxUoN5H26RkCyWXo10trpRo76osjr4rXjLag=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BZZ43xFzjLa47NNzpnKG6wuQesHEa0PZAhX8tdWH1iRXKZyA7PXq3dyzZuHGPNdh1 L9jqodq2qb44gmTXxEhR2Uyu266ErgYSMChgS6/kzTlb2Suf65CZ6GWIaTVy8a4AYp 9LhYZ57+07V7An692/cGZTOT/PIVP2/cIsBvLDv0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Joel Fernandes (Google)" , Kees Cook , Sasha Levin Subject: [PATCH AUTOSEL 4.9 13/36] pstore/ram: Do not treat empty buffers as valid Date: Tue, 8 Jan 2019 14:33:25 -0500 Message-Id: <20190108193348.123880-13-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190108193348.123880-1-sashal@kernel.org> References: <20190108193348.123880-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Joel Fernandes (Google)" [ Upstream commit 30696378f68a9e3dad6bfe55938b112e72af00c2 ] The ramoops backend currently calls persistent_ram_save_old() even if a buffer is empty. While this appears to work, it is does not seem like the right thing to do and could lead to future bugs so lets avoid that. It also prevents misleading prints in the logs which claim the buffer is valid. I got something like: found existing buffer, size 0, start 0 When I was expecting: no valid data in buffer (sig = ...) This bails out early (and reports with pr_debug()), since it's an acceptable state. Signed-off-by: Joel Fernandes (Google) Co-developed-by: Kees Cook Signed-off-by: Kees Cook Signed-off-by: Sasha Levin --- fs/pstore/ram_core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index ecdb3baa1283..11e558efd61e 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -488,6 +488,11 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig, sig ^= PERSISTENT_RAM_SIG; if (prz->buffer->sig == sig) { + if (buffer_size(prz) == 0) { + pr_debug("found existing empty buffer\n"); + return 0; + } + if (buffer_size(prz) > prz->buffer_size || buffer_start(prz) > buffer_size(prz)) pr_info("found existing invalid buffer, size %zu, start %zu\n", -- 2.19.1