From nobody Tue Jun 16 08:58:34 2026 Received: from cstnet.cn (smtp25.cstnet.cn [159.226.251.25]) (using TLSv1.2 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 94872377014; Fri, 17 Apr 2026 07:35:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=159.226.251.25 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776411353; cv=none; b=qZ3JEi4y0QxcVZQDgYqRK0pmVUHD1vwoBGL+iS0dqwqSZbdovG8vfyJcBYmrIdi/qFbp/YM1rmDPOfg2ghR59r1CFUC2LnYi73M9nCLox98Xkus/BgHxVoETk8eKYyC0mEXHuizAjk2pIUmQMzt+OUBnRnLySZJmjfCdz9ZJ9Ek= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776411353; c=relaxed/simple; bh=uj/sTiOGAy0WNSVlrUECiYhVK8QzY9DLHh3Qu8x/k/g=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=rx1hKZCtw4jNMLWqb8XhFaLrSh4izWHLHhpAaOibUloTa6m1ijkdOhXSgDVXYcImWRzOSLJIDfDqQDqpMEHE8LNKrOnrAqK4Zjg/6DgMaOm7QjGN5SZvZHhW4vJ12zKKkHto7UMxidpcuKT/6Da4QqfRmwfxN9OyJfzwxfytcxs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=iscas.ac.cn; spf=pass smtp.mailfrom=iscas.ac.cn; arc=none smtp.client-ip=159.226.251.25 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=iscas.ac.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=iscas.ac.cn Received: from localhost.localdomain (unknown [111.196.245.116]) by APP-05 (Coremail) with SMTP id zQCowADXaw_D4uFpm+fXDQ--.31691S2; Fri, 17 Apr 2026 15:35:31 +0800 (CST) From: Pengpeng Hou To: Heiko Carstens , Vasily Gorbik Cc: Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Benjamin Block , Thorsten Blum , Tigran Mkrtchyan , Kees Cook , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Pengpeng Hou Subject: [PATCH] s390/debug: reject zero-length input before trimming a newline Date: Fri, 17 Apr 2026 15:35:30 +0800 Message-ID: <20260417073530.96002-1-pengpeng@iscas.ac.cn> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: zQCowADXaw_D4uFpm+fXDQ--.31691S2 X-Coremail-Antispam: 1UD129KBjvdXoWrKFWrGF4ftr4xtrW3Jw43Jrb_yoWDWFg_Gr 97C3WkG3ZxJ342qr12yrW0qF4F9w1rGF1F9rsavrWUXryDXry3X3y8Zan5Jr13GFs8Jrs3 uwnYva13Aw10yjkaLaAFLSUrUUUUjb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUba8FF20E14v26r4j6ryUM7CY07I20VC2zVCF04k26cxKx2IYs7xG 6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8w A2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j 6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0 I7IYx2IY67AKxVWUAVWUtwAv7VC2z280aVAFwI0_Gr0_Cr1lOx8S6xCaFVCjc4AY6r1j6r 4UM4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628v n2kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7x kEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E 67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCw CI42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWU CwCI42IY6I8E87Iv67AKxVW8JVWxJwCI42IY6I8E87Iv6xkF7I0E14v26r4UJVWxJrUvcS sGvfC2KfnxnUUI43ZEXa7VUbo5l5UUUUU== X-CM-SenderInfo: pshqw1xhqjqxpvfd2hldfou0/ Content-Type: text/plain; charset="utf-8" debug_get_user_string() duplicates the userspace buffer with memdup_user_nul() and then unconditionally looks at buffer[user_len - 1] to strip a trailing newline. A zero-length write reaches this helper unchanged, so the newline trim reads before the start of the allocated buffer. Reject empty writes before accessing the last input byte. Fixes: 66a464dbc8e0 ("[PATCH] s390: debug feature changes") Signed-off-by: Pengpeng Hou Reviewed-by: Benjamin Block Reviewed-by: Vasily Gorbik Tested-by: Vasily Gorbik --- arch/s390/kernel/debug.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c index 31430e9bcfdd..2612f634e826 100644 --- a/arch/s390/kernel/debug.c +++ b/arch/s390/kernel/debug.c @@ -1414,6 +1414,9 @@ static inline char *debug_get_user_string(const char = __user *user_buf, { char *buffer; =20 + if (!user_len) + return ERR_PTR(-EINVAL); + buffer =3D memdup_user_nul(user_buf, user_len); if (IS_ERR(buffer)) return buffer; --=20 2.50.1 (Apple Git-155)