From nobody Tue Dec 30 13:12:23 2025 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 AA534C47072 for ; Wed, 15 Nov 2023 10:57:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234912AbjKOK5M (ORCPT ); Wed, 15 Nov 2023 05:57:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234098AbjKOK5L (ORCPT ); Wed, 15 Nov 2023 05:57:11 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 05CF5DA for ; Wed, 15 Nov 2023 02:57:05 -0800 (PST) Received: from kwepemi500008.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4SVg4338DpzNmJ3; Wed, 15 Nov 2023 18:52:51 +0800 (CST) Received: from huawei.com (10.90.53.73) by kwepemi500008.china.huawei.com (7.221.188.139) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Wed, 15 Nov 2023 18:57:03 +0800 From: Jinjie Ruan To: , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" CC: Subject: [PATCH] x86: Fix 32-bit compatible userspace write size overflow error Date: Wed, 15 Nov 2023 18:56:26 +0800 Message-ID: <20231115105626.953273-1-ruanjinjie@huawei.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.90.53.73] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemi500008.china.huawei.com (7.221.188.139) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" For 32-bit compatible userspace program, write with size =3D -1 return not -1 but unexpected other values, which is due to the __access_ok() check is insufficient. The specified "ptr + size" is greater than 32-bit limit and should return -EFAULT, but it is not checked and can not catch the overflow error. Fix above error by checking 32-bit limit if it is 32-bit compatible userspace program. How to reproduce: The test program is as below: root@syzkaller:~# cat test.c #include #include #include #include #include #include #define pinfo(fmt, args...) \ fprintf(stderr, "[INFO][%s][%d][%s]:"fmt, \ __FILE__,__LINE__,__func__,##args) #undef SIZE_MAX #define SIZE_MAX -1 int main() { char wbuf[3] =3D { 'x', 'y', 'z' }; char *path =3D "write.tmp"; int ret; int fd =3D open(path, O_RDWR | O_CREAT); if (fd<0) { pinfo("fd=3D%d\n", fd); exit(-1); } assert(write(fd, wbuf, 3) =3D=3D 3); ret =3D write (fd, wbuf, SIZE_MAX); pinfo("ret=3D%d\n", ret); pinfo("size_max=3D%d\n",SIZE_MAX); assert(ret=3D=3D-1); close(fd); pinfo("INFO: end\n"); return 0; } Before applying this patch, userspace 32-bit program return 3799 if the write size =3D -1 as below: root@syzkaller:~# gcc test.c -o test root@syzkaller:~# gcc -m32 test.c -o test32 root@syzkaller:~# ./test [INFO][test.c][32][main]:ret=3D-1 [INFO][test.c][33][main]:size_max=3D-1 [INFO][test.c][36][main]:INFO: end root@syzkaller:~# ./test32 [INFO][test.c][32][main]:ret=3D3799 [INFO][test.c][33][main]:size_max=3D-1 test32: test.c:34: main: Assertion `ret=3D=3D-1' failed. Aborted After applying this patch, userspace 32-bit program return -1 if the write size =3D -1 as expected as below: root@syzkaller:~# gcc test.c -o test root@syzkaller:~# gcc -m32 test.c -o test32 root@syzkaller:~# ./test [INFO][test.c][32][main]:ret=3D-1 [INFO][test.c][33][main]:size_max=3D-1 [INFO][test.c][36][main]:INFO: end root@syzkaller:~# ./test32 [INFO][test.c][32][main]:ret=3D-1 [INFO][test.c][33][main]:size_max=3D-1 [INFO][test.c][36][main]:INFO: end Fixes: b9bd9f605c4a ("x86: uaccess: move 32-bit and 64-bit parts into prope= r header") Signed-off-by: Jinjie Ruan --- arch/x86/include/asm/uaccess_64.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uacce= ss_64.h index f2c02e4469cc..9febfbca3a88 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -88,6 +88,12 @@ static inline bool __access_ok(const void __user *ptr, u= nsigned long size) return valid_user_address(ptr); } else { unsigned long sum =3D size + (unsigned long)ptr; + +#ifdef CONFIG_COMPAT + if (in_ia32_syscall()) + return valid_user_address(sum) && + sum >=3D (unsigned long)ptr && sum < UL(0x100000000); +#endif return valid_user_address(sum) && sum >=3D (unsigned long)ptr; } } --=20 2.34.1