From patchwork Tue Oct 19 14:45:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geert Uytterhoeven X-Patchwork-Id: 12570139 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A7E0C433F5 for ; Tue, 19 Oct 2021 14:45:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84656611EF for ; Tue, 19 Oct 2021 14:45:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232548AbhJSOsL (ORCPT ); Tue, 19 Oct 2021 10:48:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232521AbhJSOr5 (ORCPT ); Tue, 19 Oct 2021 10:47:57 -0400 Received: from baptiste.telenet-ops.be (baptiste.telenet-ops.be [IPv6:2a02:1800:120:4::f00:13]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C616BC0617A7 for ; Tue, 19 Oct 2021 07:45:32 -0700 (PDT) Received: from ramsan.of.borg ([IPv6:2a02:1810:ac12:ed20:b4c3:ba80:54db:46f]) by baptiste.telenet-ops.be with bizsmtp id 7qlT2600F12AN0U01qlTMx; Tue, 19 Oct 2021 16:45:30 +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 1mcqMp-006B4Q-CD; Tue, 19 Oct 2021 16:45:27 +0200 Received: from geert by rox.of.borg with local (Exim 4.93) (envelope-from ) id 1mcqMn-00FAAX-Jp; Tue, 19 Oct 2021 16:45:25 +0200 From: Geert Uytterhoeven To: Miguel Ojeda Cc: Robin van der Gracht , Rob Herring , Paul Burton , 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 v8 03/21] auxdisplay: img-ascii-lcd: Fix lock-up when displaying empty string Date: Tue, 19 Oct 2021 16:45:02 +0200 Message-Id: <20211019144520.3613926-4-geert@linux-m68k.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211019144520.3613926-1-geert@linux-m68k.org> References: <20211019144520.3613926-1-geert@linux-m68k.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-mips@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. v8: - No changes, v7: - No changes, 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;