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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0993C43219 for ; Mon, 31 Jan 2022 11:31:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378880AbiAaL31 (ORCPT ); Mon, 31 Jan 2022 06:29:27 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:52206 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378381AbiAaLUG (ORCPT ); Mon, 31 Jan 2022 06:20:06 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A9B5F6114C; Mon, 31 Jan 2022 11:20:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7161BC340E8; Mon, 31 Jan 2022 11:20:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643628005; bh=yo2HdgKuwvwA7p/MnrO/cT8+coYM6M44nJwMQhWhpX8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xPTEsvTl44KUnQsk+BA/dkU+RZtvVjJy1NgozRDYBMFlj7AlFLw5CzBzfvsT83XY0 jIP3a5xHNdVxaZ+i9JdHQe8IjSXoSvk4gJ7Y7UZKCiT0uRjNfMttjVThGZ0l5YNF+d daaVkfwkzyLvITMgZlDi95v/x7EkxZymFz1szRCE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mark Rutland , Evgenii Stepanov , Catalin Marinas Subject: [PATCH 5.16 061/200] arm64: extable: fix load_unaligned_zeropad() reg indices Date: Mon, 31 Jan 2022 11:55:24 +0100 Message-Id: <20220131105235.627000123@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220131105233.561926043@linuxfoundation.org> References: <20220131105233.561926043@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Evgenii Stepanov commit 3758a6c74e08bdc15ccccd6872a6ad37d165239a upstream. In ex_handler_load_unaligned_zeropad() we erroneously extract the data and addr register indices from ex->type rather than ex->data. As ex->type will contain EX_TYPE_LOAD_UNALIGNED_ZEROPAD (i.e. 4): * We'll always treat X0 as the address register, since EX_DATA_REG_ADDR is extracted from bits [9:5]. Thus, we may attempt to dereference an arbitrary address as X0 may hold an arbitrary value. * We'll always treat X4 as the data register, since EX_DATA_REG_DATA is extracted from bits [4:0]. Thus we will corrupt X4 and cause arbitrary behaviour within load_unaligned_zeropad() and its caller. Fix this by extracting both values from ex->data as originally intended. On an MTE-enabled QEMU image we are hitting the following crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Call trace: fixup_exception+0xc4/0x108 __do_kernel_fault+0x3c/0x268 do_tag_check_fault+0x3c/0x104 do_mem_abort+0x44/0xf4 el1_abort+0x40/0x64 el1h_64_sync_handler+0x60/0xa0 el1h_64_sync+0x7c/0x80 link_path_walk+0x150/0x344 path_openat+0xa0/0x7dc do_filp_open+0xb8/0x168 do_sys_openat2+0x88/0x17c __arm64_sys_openat+0x74/0xa0 invoke_syscall+0x48/0x148 el0_svc_common+0xb8/0xf8 do_el0_svc+0x28/0x88 el0_svc+0x24/0x84 el0t_64_sync_handler+0x88/0xec el0t_64_sync+0x1b4/0x1b8 Code: f8695a69 71007d1f 540000e0 927df12a (f940014a) Fixes: 753b32368705 ("arm64: extable: add load_unaligned_zeropad() handler") Cc: # 5.16.x Reviewed-by: Mark Rutland Signed-off-by: Evgenii Stepanov Link: https://lore.kernel.org/r/20220125182217.2605202-1-eugenis@google.com Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/extable.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -43,8 +43,8 @@ static bool ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, struct pt_regs *regs) { - int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type); - int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type); + int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data); + int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data); unsigned long data, addr, offset; addr = pt_regs_read_reg(regs, reg_addr);