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=unavailable 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 653B3C10F14 for ; Thu, 3 Oct 2019 17:36:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F3652086A for ; Thu, 3 Oct 2019 17:36:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570124188; bh=E4yPYwc32cIU2DIgfQp7vP06Bppdzxn0qHcM/XOaOkw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sWSoz5ZOsKpIn7okWn5RBfSPvs0k6GYZFyomQrPv4Ag11Fa7rl7ZcLJJo4A+PZL33 zTexVEb3ROJAfWiuqnHDvED1e7nCtyvDDRhiE+P+9D5UXPh9Ty1ncde7ceI6LpOZXJ SB7WRObYToKa+RP05sbsOWjD7AZJXl9vDocERZlU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388682AbfJCRg1 (ORCPT ); Thu, 3 Oct 2019 13:36:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:51164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732480AbfJCQEw (ORCPT ); Thu, 3 Oct 2019 12:04:52 -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 45A5021D81; Thu, 3 Oct 2019 16:04:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570118691; bh=E4yPYwc32cIU2DIgfQp7vP06Bppdzxn0qHcM/XOaOkw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ke1xdcmudqcykcOZg4dcEkZISz2xhUafiGOyY8LydMpuN/UumesIHLQD32iMciBez YnnwN3bg096MWrA9zCTPRynqZhdFgpxELvVRzCUgVdN0MaNsdZ37biqUwg6vp42Ivd oMfOkqzSzgFyl+TBX8LkwhV+WN6EA7JGlZCWqtok= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, rostedt@goodmis.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vincent Whitchurch , Sergey Senozhatsky , Petr Mladek , Sasha Levin Subject: [PATCH 4.9 102/129] printk: Do not lose last line in kmsg buffer dump Date: Thu, 3 Oct 2019 17:53:45 +0200 Message-Id: <20191003154405.768526041@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191003154318.081116689@linuxfoundation.org> References: <20191003154318.081116689@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: Vincent Whitchurch [ Upstream commit b46eff55ad5bd98e746c0a7022fe7ee071de5fee ] kmsg_dump_get_buffer() is supposed to select all the youngest log messages which fit into the provided buffer. It determines the correct start index by using msg_print_text() with a NULL buffer to calculate the size of each entry. However, when performing the actual writes, msg_print_text() only writes the entry to the buffer if the written len is lesser than the size of the buffer. So if the lengths of the selected youngest log messages happen to precisely fill up the provided buffer, the last log message is not included. We don't want to modify msg_print_text() to fill up the buffer and start returning a length which is equal to the size of the buffer, since callers of its other users, such as kmsg_dump_get_line(), depend upon the current behaviour. Instead, fix kmsg_dump_get_buffer() to compensate for this. For example, with the following two final prints: [ 6.427502] AAAAAAAAAAAAA [ 6.427769] BBBBBBBB12345 A dump of a 64-byte buffer filled by kmsg_dump_get_buffer(), before this patch: 00000000: 3c 30 3e 5b 20 20 20 20 36 2e 35 32 32 31 39 37 <0>[ 6.522197 00000010: 5d 20 41 41 41 41 41 41 41 41 41 41 41 41 41 0a ] AAAAAAAAAAAAA. 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ After this patch: 00000000: 3c 30 3e 5b 20 20 20 20 36 2e 34 35 36 36 37 38 <0>[ 6.456678 00000010: 5d 20 42 42 42 42 42 42 42 42 31 32 33 34 35 0a ] BBBBBBBB12345. 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ Link: http://lkml.kernel.org/r/20190711142937.4083-1-vincent.whitchurch@axis.com Fixes: e2ae715d66bf4bec ("kmsg - kmsg_dump() use iterator to receive log buffer content") To: rostedt@goodmis.org Cc: linux-kernel@vger.kernel.org Cc: # v3.5+ Signed-off-by: Vincent Whitchurch Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin --- kernel/printk/printk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index df348d4eeb265..6607d77afe55a 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3131,7 +3131,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, /* move first record forward until length fits into the buffer */ seq = dumper->cur_seq; idx = dumper->cur_idx; - while (l > size && seq < dumper->next_seq) { + while (l >= size && seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); l -= msg_print_text(msg, true, NULL, 0); -- 2.20.1