From mboxrd@z Thu Jan 1 00:00:00 1970 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 B1657CA9EA0 for ; Fri, 25 Oct 2019 13:58:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 85DC0222C9 for ; Fri, 25 Oct 2019 13:58:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572011934; bh=RPu44RCFgWUoB0ffJytntIbu2rU10TJxyU2PzThNAQA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sgW96uivTZS6RthZV2CXencG6AcWk9WCBSPfqRk52/XpX9BL6zr6bR+uDPn/FzG6P OV8rixPscDE/39cL3bk2qZ65WAANQQe85Tq6YD5P8x32prVvVz/e35fGB5x5pGJIpy /UaLXs46uisYcaxSGyiimdHjGGbN/IE2ujzc3M/4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2632878AbfJYN6x (ORCPT ); Fri, 25 Oct 2019 09:58:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:54488 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389278AbfJYN6v (ORCPT ); Fri, 25 Oct 2019 09:58:51 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AD38D222C9; Fri, 25 Oct 2019 13:58:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572011930; bh=RPu44RCFgWUoB0ffJytntIbu2rU10TJxyU2PzThNAQA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q2LB97n30c5KxDuFjEQoBki1KsgsrFXwd/ayNi9hZHGpwAp9J1tW7DZGvScOjx+32 DxkVzEcaUW/xIod9AStp+M87PaBvjADsff4fhAqa+odaF2iBlVZ9lkhlKD+pFa68Le h8jMnhh79Bl3wBhO2R4RXYDpF3lI4nT4wWOTwyAE= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Daniel Axtens , Michael Ellerman , Sasha Levin , linuxppc-dev@lists.ozlabs.org Subject: [PATCH AUTOSEL 4.4 04/16] powerpc/pseries/hvconsole: Fix stack overread via udbg Date: Fri, 25 Oct 2019 09:58:28 -0400 Message-Id: <20191025135842.25977-4-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191025135842.25977-1-sashal@kernel.org> References: <20191025135842.25977-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Axtens [ Upstream commit 934bda59f286d0221f1a3ebab7f5156a996cc37d ] While developing KASAN for 64-bit book3s, I hit the following stack over-read. It occurs because the hypercall to put characters onto the terminal takes 2 longs (128 bits/16 bytes) of characters at a time, and so hvc_put_chars() would unconditionally copy 16 bytes from the argument buffer, regardless of supplied length. However, udbg_hvc_putc() can call hvc_put_chars() with a single-byte buffer, leading to the error. ================================================================== BUG: KASAN: stack-out-of-bounds in hvc_put_chars+0xdc/0x110 Read of size 8 at addr c0000000023e7a90 by task swapper/0 CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.0-rc2-next-20190528-02824-g048a6ab4835b #113 Call Trace: dump_stack+0x104/0x154 (unreliable) print_address_description+0xa0/0x30c __kasan_report+0x20c/0x224 kasan_report+0x18/0x30 __asan_report_load8_noabort+0x24/0x40 hvc_put_chars+0xdc/0x110 hvterm_raw_put_chars+0x9c/0x110 udbg_hvc_putc+0x154/0x200 udbg_write+0xf0/0x240 console_unlock+0x868/0xd30 register_console+0x970/0xe90 register_early_udbg_console+0xf8/0x114 setup_arch+0x108/0x790 start_kernel+0x104/0x784 start_here_common+0x1c/0x534 Memory state around the buggy address: c0000000023e7980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 c0000000023e7a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 >c0000000023e7a80: f1 f1 01 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 ^ c0000000023e7b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 c0000000023e7b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== Document that a 16-byte buffer is requred, and provide it in udbg. Signed-off-by: Daniel Axtens Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/platforms/pseries/hvconsole.c | 2 +- drivers/tty/hvc/hvc_vio.c | 16 +++++++++++++++- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/platforms/pseries/hvconsole.c b/arch/powerpc/platforms/pseries/hvconsole.c index 849b29b3e9ae0..954ef27128f22 100644 --- a/arch/powerpc/platforms/pseries/hvconsole.c +++ b/arch/powerpc/platforms/pseries/hvconsole.c @@ -62,7 +62,7 @@ EXPORT_SYMBOL(hvc_get_chars); * @vtermno: The vtermno or unit_address of the adapter from which the data * originated. * @buf: The character buffer that contains the character data to send to - * firmware. + * firmware. Must be at least 16 bytes, even if count is less than 16. * @count: Send this number of characters. */ int hvc_put_chars(uint32_t vtermno, const char *buf, int count) diff --git a/drivers/tty/hvc/hvc_vio.c b/drivers/tty/hvc/hvc_vio.c index f575a9b5ede7b..1d671d058dcb0 100644 --- a/drivers/tty/hvc/hvc_vio.c +++ b/drivers/tty/hvc/hvc_vio.c @@ -122,6 +122,14 @@ static int hvterm_raw_get_chars(uint32_t vtermno, char *buf, int count) return got; } +/** + * hvterm_raw_put_chars: send characters to firmware for given vterm adapter + * @vtermno: The virtual terminal number. + * @buf: The characters to send. Because of the underlying hypercall in + * hvc_put_chars(), this buffer must be at least 16 bytes long, even if + * you are sending fewer chars. + * @count: number of chars to send. + */ static int hvterm_raw_put_chars(uint32_t vtermno, const char *buf, int count) { struct hvterm_priv *pv = hvterm_privs[vtermno]; @@ -234,6 +242,7 @@ static const struct hv_ops hvterm_hvsi_ops = { static void udbg_hvc_putc(char c) { int count = -1; + unsigned char bounce_buffer[16]; if (!hvterm_privs[0]) return; @@ -244,7 +253,12 @@ static void udbg_hvc_putc(char c) do { switch(hvterm_privs[0]->proto) { case HV_PROTOCOL_RAW: - count = hvterm_raw_put_chars(0, &c, 1); + /* + * hvterm_raw_put_chars requires at least a 16-byte + * buffer, so go via the bounce buffer + */ + bounce_buffer[0] = c; + count = hvterm_raw_put_chars(0, bounce_buffer, 1); break; case HV_PROTOCOL_HVSI: count = hvterm_hvsi_put_chars(0, &c, 1); -- 2.20.1