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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 E8FCEC32792 for ; Thu, 3 Oct 2019 16:58:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B51342070B for ; Thu, 3 Oct 2019 16:58:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570121893; bh=BZapDg6ZGXM9Rg5kPcRilfrz2LUQyzrkxIwwMOM1Xy0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=M/DMqp2N33MknY6ULXxxeBiGc/opeZfP3uSWIdFwnxF7VMWnvUEoqy6OPC2aP68iD 9rQtBj9HPeXDzHYQYh7M/agV0yYdLtHU/utv3Lpzr3MUv4cOgOcZh3MhW8pV/qk8sv PM1qld5Je35NFk197ek0iZyuu2uDukkXDH6v8hPI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404638AbfJCQtE (ORCPT ); Thu, 3 Oct 2019 12:49:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:35274 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405791AbfJCQtB (ORCPT ); Thu, 3 Oct 2019 12:49:01 -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 F2C1220865; Thu, 3 Oct 2019 16:48:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570121340; bh=BZapDg6ZGXM9Rg5kPcRilfrz2LUQyzrkxIwwMOM1Xy0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q7qm/0phn53sYjcPyW1RMHga51bVgCwWoz33em4Bksg2TLE59+d4Eh/4sDEazx9DU yHYa+B+PvZQIGvbYQmxRR8l+PLtgwzXsrm/TShuwGghQ9o7v4OQex2X/GWMsZpkVmI 3SuKfljokjEkuPz+AdmIE5zgfFwcLZhUVtWOg8T8= 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 Subject: [PATCH 5.3 242/344] printk: Do not lose last line in kmsg buffer dump Date: Thu, 3 Oct 2019 17:53:27 +0200 Message-Id: <20191003154604.278696964@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191003154540.062170222@linuxfoundation.org> References: <20191003154540.062170222@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 commit c9dccacfccc72c32692eedff4a27a4b0833a2afd upstream. 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: Greg Kroah-Hartman --- kernel/printk/printk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3274,7 +3274,7 @@ bool kmsg_dump_get_buffer(struct kmsg_du /* 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, time, NULL, 0);