From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33776 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727644AbeIMTDt (ORCPT ); Thu, 13 Sep 2018 15:03:49 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andrey Ryabinin , icytxw@gmail.com, Andrew Morton , Alexander Potapenko , Dmitry Vyukov , Linus Torvalds , Sasha Levin Subject: [PATCH 4.18 059/197] mm/fadvise.c: fix signed overflow UBSAN complaint Date: Thu, 13 Sep 2018 15:30:08 +0200 Message-Id: <20180913131843.885444839@linuxfoundation.org> In-Reply-To: <20180913131841.568116777@linuxfoundation.org> References: <20180913131841.568116777@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrey Ryabinin [ Upstream commit a718e28f538441a3b6612da9ff226973376cdf0f ] Signed integer overflow is undefined according to the C standard. The overflow in ksys_fadvise64_64() is deliberate, but since it is signed overflow, UBSAN complains: UBSAN: Undefined behaviour in mm/fadvise.c:76:10 signed integer overflow: 4 + 9223372036854775805 cannot be represented in type 'long long int' Use unsigned types to do math. Unsigned overflow is defined so UBSAN will not complain about it. This patch doesn't change generated code. [akpm@linux-foundation.org: add comment explaining the casts] Link: http://lkml.kernel.org/r/20180629184453.7614-1-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin Reported-by: Reviewed-by: Andrew Morton Cc: Alexander Potapenko Cc: Dmitry Vyukov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/fadvise.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/mm/fadvise.c +++ b/mm/fadvise.c @@ -72,8 +72,12 @@ int ksys_fadvise64_64(int fd, loff_t off goto out; } - /* Careful about overflows. Len == 0 means "as much as possible" */ - endbyte = offset + len; + /* + * Careful about overflows. Len == 0 means "as much as possible". Use + * unsigned math because signed overflows are undefined and UBSan + * complains. + */ + endbyte = (u64)offset + (u64)len; if (!len || endbyte < len) endbyte = -1; else