From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B4E7A3E9C14; Tue, 12 May 2026 17:47:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778608053; cv=none; b=Tei2aFrmGKhQBtMsSFBIE+guywKhrncCwEqUndwx91u/QgvlDp2BXKdTDqJbBPBc2ZbyVekCXJtUrQI5BaYekofpu223GVNLJ10lt8L9ySmw4MTaUR7BafCf1hf2Fawd1PyCYQVfo/YNw4aSW4uFO/SsiHGuNrnObqcooYdkwrI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778608053; c=relaxed/simple; bh=bN8bL2G62fFXSsI/ZAXK66OP8QadpxuVBweQ6elsQmc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DpzkC7K9lwlwX2DuLOmcxgGD7jsbk7Z3pe+HaYYqYDWK3sOD5qrU1qsja6rigJVKjfzR1cpz7iecaJOGk1MpvbnStr1YNeOsPgVp7O4nog3kZRl+ocXdgLcsty1tA34cbdmtFZmaoCEe7tWC28Yq4TYFR1999+A37XOhPCTCHlU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CcA/qDFo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="CcA/qDFo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E324C2BCB0; Tue, 12 May 2026 17:47:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778608053; bh=bN8bL2G62fFXSsI/ZAXK66OP8QadpxuVBweQ6elsQmc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CcA/qDFo+th4BQs2dBzmpzAtc2qVYXuAwXPwxOqpOugCjrtsHzV88unDTVTxMyWXV w2HHJjNwlJMtPC6PV1B7lii9AUepXqtwluyF1y92QiuuWu6tLQiXfoeXxrXc+zmTeq D7MF+9xqgIuKJmBAn2b/DWf3kLq+uzHLHC0B5DnI= 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 6.12 136/206] s390/debug: Reject zero-length input in debug_input_flush_fn() Date: Tue, 12 May 2026 19:39:48 +0200 Message-ID: <20260512173935.739820236@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260512173932.810559588@linuxfoundation.org> References: <20260512173932.810559588@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-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 @@ -1432,6 +1432,11 @@ 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) {