From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBDDA2628D; Sat, 30 May 2026 17:55:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780163705; cv=none; b=KmCwtS/oag4Ier/LXqv7siiPst75SoLjhm/f9mb9fWIGzKwY/r97akpqQ9b5YGB03mHzYCuTaX5Tsn2xpoB4CEmpAydVKOFd8EAZQcFvoo6+RhGn8HVg1qlsh9aWb2EZVKrvEnAW611pdFi2yz9VSYtVGrMpXv2SXNShJTUE408= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780163705; c=relaxed/simple; bh=SEyp8eeqA4TDjN4cy6ZGFsAI2cFbr31qtLMfFawDwYE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ixi7VywTj7HDE01rmdOw+GV2o492XNIImI1oxr6/w1lnyvySf7nrbuVYX+U+H7CRPYiiNbiGqja7MCJ+Zqj25jGya9O+lh77XcV/4MjVOryt4lwQzEqL3WOWyFYrc7FRiuLXjzRCUjQIO2wuhiUz1+7wRJDDRCMx+0gmh1x4RWA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=iTCUswbb; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="iTCUswbb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C99C1F00893; Sat, 30 May 2026 17:55:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780163704; bh=+O9M9zYEU59O3u9j4wZDvzR4qkAJl5lGWD3/i9zL8AY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=iTCUswbbOC9XHfmBaJsBXca3YTCru56QvizcSimhu0QpqyCwpNwSFR2WDna1ntf3x o2ZIdcsmgkPtSIXdOlf27fKnQ1ORArRJZokKhRMv4iNnodeJsE7tbdtPN+J+JmZIzF OPC3gK8AWV9nR7X2qkl+GJ3G78MPzLFJSV+MR7nw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Heiko Carstens , Vasily Gorbik , Alexander Gordeev Subject: [PATCH 5.15 338/776] s390/debug: Reject zero-length input in debug_input_flush_fn() Date: Sat, 30 May 2026 18:00:52 +0200 Message-ID: <20260530160249.307998753@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vasily Gorbik commit e14622a7584f9608927c59a7d6ae4a0999dc545e upstream. debug_input_flush_fn() always copies one byte from the userspace buffer with copy_from_user() regardless of the supplied write length. A zero-length write therefore reads one byte beyond the caller's buffer. If the stale byte happens to be '-' or a digit the debug log is silently flushed. With an unmapped buffer the call returns -EFAULT. Reject zero-length writes before copying from userspace. Cc: stable@vger.kernel.org # v5.10+ Acked-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Alexander Gordeev Signed-off-by: Greg Kroah-Hartman --- arch/s390/kernel/debug.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/arch/s390/kernel/debug.c +++ b/arch/s390/kernel/debug.c @@ -1444,6 +1444,11 @@ static int debug_input_flush_fn(debug_in char input_buf[1]; int rc = user_len; + if (!user_len) { + rc = -EINVAL; + goto out; + } + if (user_len > 0x10000) user_len = 0x10000; if (*offset != 0) {