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 8A97EC4332F for ; Tue, 8 Nov 2022 19:52:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229764AbiKHTw4 (ORCPT ); Tue, 8 Nov 2022 14:52:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229774AbiKHTwz (ORCPT ); Tue, 8 Nov 2022 14:52:55 -0500 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 120F67057F; Tue, 8 Nov 2022 11:52:53 -0800 (PST) Received: from pwmachine.numericable.fr (85-170-25-210.rev.numericable.fr [85.170.25.210]) by linux.microsoft.com (Postfix) with ESMTPSA id 100FB20B9F81; Tue, 8 Nov 2022 11:52:48 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 100FB20B9F81 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1667937172; bh=aV1rbRcoT8elrIFvcswWnTb6/2G/r5XMttMTu6HgEWE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rNA91l5NyZRNSqXKVvrOFtfVRTnClAzSHuIB0O3Egn/SS6gqzKq3v7ZKmQBR/jCpy mgmLPKxd59MfGA18pKlh2CT9mEP1YYypTZe/p83XNEV2xlMr6zqKrK9/5hjRy1klb0 USlF3Ft41AuAO7/QWRSjFyu3ezjq7SIq6BQwfc2U= From: Francis Laniel To: linux-kernel@vger.kernel.org Cc: Alban Crequy , Alban Crequy , Francis Laniel , Andrew Morton , Andrii Nakryiko , Mykola Lysenko , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , linux-mm@kvack.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [RFC PATCH v1 1/2] maccess: fix writing offset in case of fault in strncpy_from_kernel_nofault() Date: Tue, 8 Nov 2022 20:52:06 +0100 Message-Id: <20221108195211.214025-2-flaniel@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20221108195211.214025-1-flaniel@linux.microsoft.com> References: <20221108195211.214025-1-flaniel@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org From: Alban Crequy If a page fault occurs while copying the first byte, this function resets one byte before dst. As a consequence, an address could be modified and leaded to kernel crashes if case the modified address was accessed later. Signed-off-by: Alban Crequy Tested-by: Francis Laniel --- mm/maccess.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/maccess.c b/mm/maccess.c index 5f4d240f67ec..074f6b086671 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -97,7 +97,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) return src - unsafe_addr; Efault: pagefault_enable(); - dst[-1] = '\0'; + dst[0] = '\0'; return -EFAULT; } -- 2.25.1