From patchwork Tue Sep 14 14:38:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geert Uytterhoeven X-Patchwork-Id: 512460 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 5CCBBC43219 for ; Tue, 14 Sep 2021 14:38:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 48C96610E6 for ; Tue, 14 Sep 2021 14:38:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234106AbhINOkE (ORCPT ); Tue, 14 Sep 2021 10:40:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233929AbhINOkC (ORCPT ); Tue, 14 Sep 2021 10:40:02 -0400 Received: from xavier.telenet-ops.be (xavier.telenet-ops.be [IPv6:2a02:1800:120:4::f00:14]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED547C0613CF for ; Tue, 14 Sep 2021 07:38:43 -0700 (PDT) Received: from ramsan.of.borg ([IPv6:2a02:1810:ac12:ed20:d46f:7eb5:4a37:9d14]) by xavier.telenet-ops.be with bizsmtp id tqef2500K2aSKa101qef6G; Tue, 14 Sep 2021 16:38:41 +0200 Received: from rox.of.borg ([192.168.97.57]) by ramsan.of.borg with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1mQ9a2-004VGf-Vv; Tue, 14 Sep 2021 16:38:38 +0200 Received: from geert by rox.of.borg with local (Exim 4.93) (envelope-from ) id 1mQ9a2-0028y9-FY; Tue, 14 Sep 2021 16:38:38 +0200 From: Geert Uytterhoeven To: Robin van der Gracht , Miguel Ojeda , Rob Herring , Paul Burton Cc: Greg Kroah-Hartman , Pavel Machek , Marek Behun , devicetree@vger.kernel.org, linux-leds@vger.kernel.org, linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH v6 03/19] auxdisplay: img-ascii-lcd: Fix lock-up when displaying empty string Date: Tue, 14 Sep 2021 16:38:19 +0200 Message-Id: <20210914143835.511051-4-geert@linux-m68k.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210914143835.511051-1-geert@linux-m68k.org> References: <20210914143835.511051-1-geert@linux-m68k.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org While writing an empty string to a device attribute is a no-op, and thus does not need explicit safeguards, the user can still write a single newline to an attribute file: echo > .../message If that happens, img_ascii_lcd_display() trims the newline, yielding an empty string, and causing an infinite loop in img_ascii_lcd_scroll(). Fix this by adding a check for empty strings. Clear the display in case one is encountered. Fixes: 0cad855fbd083ee5 ("auxdisplay: img-ascii-lcd: driver for simple ASCII LCD displays") Signed-off-by: Geert Uytterhoeven --- Untested with img-ascii-lcd, but triggered with my initial version of linedisp. v6: - No changes, v5: - No changes, v4: - No changes, v3: - No changes, v2: - No changes. --- drivers/auxdisplay/img-ascii-lcd.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/auxdisplay/img-ascii-lcd.c b/drivers/auxdisplay/img-ascii-lcd.c index 1cce409ce5cacbc8..e33ce0151cdfd150 100644 --- a/drivers/auxdisplay/img-ascii-lcd.c +++ b/drivers/auxdisplay/img-ascii-lcd.c @@ -280,6 +280,16 @@ static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx, if (msg[count - 1] == '\n') count--; + if (!count) { + /* clear the LCD */ + devm_kfree(&ctx->pdev->dev, ctx->message); + ctx->message = NULL; + ctx->message_len = 0; + memset(ctx->curr, ' ', ctx->cfg->num_chars); + ctx->cfg->update(ctx); + return 0; + } + new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL); if (!new_msg) return -ENOMEM;