From nobody Mon Feb 9 22:05:14 2026 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A62B15573F; Mon, 27 Jan 2025 15:32:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.21 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737991961; cv=none; b=pK9yKZf4C2C3Hhh/5p1efyufnYY8I5YRSAHzpui4Ct9GXzWwNzpFe3V2/G2SfQv6SuRcdP1TVTWROkF6YpOGA/ypqFTslbBgnuYYYcjWjGMOP6beA6SAlGrHl/8Q58ZviIV6BwmFN0WPVQA7hmE5RYrNtxVSsST2zGwHHKc8WzY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737991961; c=relaxed/simple; bh=BESMgBwWxqrQ8LgJ1bKgxPdpSxs9VxfJab81KkvW+Nc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tU3v789+Lsw5KgX42STNn+Po7b5k4ISfdvsVmG1tA0DvGtcZvmO/FNMVv87NVkoqrX4JP827OWEULHHYqo/dPrTcqhSUAyd4P0yeyB5NrASVH/RkG45811SGIYxQqEZrp4GfB3SGNbHAh0p6QrkleRM1EMrLzcgOjnLSDq2SBhI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=KMYRJKFy; arc=none smtp.client-ip=198.175.65.21 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="KMYRJKFy" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1737991960; x=1769527960; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=BESMgBwWxqrQ8LgJ1bKgxPdpSxs9VxfJab81KkvW+Nc=; b=KMYRJKFyM8t+wwcP/0Sgqmwh7aP3HoYjU6qhCQUhx6uYwo4murXS1PUS v7ELSx0d1cpL+5W/87KGRstsWS+MQKUxdav4enz6u4CP3ecQNDUvPVTmX QstqlCwOsDVgtLXmOLqj98fQoJByCHxvelpgOdNMH67TGAGzEgRet/pY7 JcM6+ar6YinbSm4nTnRRI/on4+i7B2YbySjdyq5PegQ1wPUrLjMJavAli XyYs0w1ijPx2bRg9gFS57w7ftpNP8YDuVhtrz2CVqV2SJSuTWi4Cw7qSW 1E/FiYM4zgWfkI/VHDn4K8tuj9iT9ydyJFVDMCAObDJ1RICrTRfo0ooJY A==; X-CSE-ConnectionGUID: 4xi4M4//R++FW6Ym2n4M8Q== X-CSE-MsgGUID: OFcEJ+lcQveffwZbTHubWA== X-IronPort-AV: E=McAfee;i="6700,10204,11328"; a="38344130" X-IronPort-AV: E=Sophos;i="6.13,238,1732608000"; d="scan'208";a="38344130" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2025 07:32:40 -0800 X-CSE-ConnectionGUID: 8SI6fRs7Toq1GrCbTqua3w== X-CSE-MsgGUID: TkKOcupjQ1W0VXRogpqXpQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,238,1732608000"; d="scan'208";a="108991074" Received: from oandoniu-mobl3.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.244.88]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2025 07:32:37 -0800 From: Maciej Wieczor-Retman To: shuah@kernel.org, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, bp@alien8.de, mingo@redhat.com, tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kirill@shutemov.name, maciej.wieczor-retman@intel.com Subject: [PATCH v6 3/3] selftests/lam: Test get_user() LAM pointer handling Date: Mon, 27 Jan 2025 16:31:57 +0100 Message-ID: <1624d9d1b9502517053a056652d50dc5d26884ac.1737990375.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Recent change in how get_user() handles pointers [1] has a specific case for LAM. It assigns a different bitmask that's later used to check whether a pointer comes from userland in get_user(). Add test case to LAM that utilizes a ioctl (FIOASYNC) syscall which uses get_user() in its implementation. Execute the syscall with differently tagged pointers to verify that valid user pointers are passing through and invalid kernel/non-canonical pointers are not. [1] https://lore.kernel.org/all/20241024013214.129639-1-torvalds@linux-foun= dation.org/ Signed-off-by: Maciej Wieczor-Retman --- Changelog v6: - Update la57 checking function name. - Fix typo and add comment to the ioctl() usage. Changelog v4: - Use the changed cpu_has_la57() instead of mmap() to figure out current paging level. - Apply Kirill's other comments: Remove redundant always true check, close the ioctl file before exiting, change mapping size to PAGE_SIZE so it looks less odd. - Turn this patch into a series and move some text to the cover letter. Changelog v3: - mmap the pointer passed to get_user to high address if 5 level paging is enabled and to low address if 4 level paging is enabled. Changelog v2: - Use mmap with HIGH_ADDR to check if we're in 5 or 4 level pagetables. tools/testing/selftests/x86/lam.c | 108 ++++++++++++++++++++++++++++++ 1 file changed, 108 insertions(+) diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x8= 6/lam.c index 140011bc39c0..6e013dfac35e 100644 --- a/tools/testing/selftests/x86/lam.c +++ b/tools/testing/selftests/x86/lam.c @@ -4,6 +4,7 @@ #include #include #include +#include #include #include #include @@ -43,7 +44,15 @@ #define FUNC_INHERITE 0x20 #define FUNC_PASID 0x40 =20 +/* get_user() pointer test cases */ +#define GET_USER_USER 0 +#define GET_USER_KERNEL_TOP 1 +#define GET_USER_KERNEL_BOT 2 +#define GET_USER_KERNEL 3 + #define TEST_MASK 0x7f +#define L5_SIGN_EXT_MASK (0xFFUL << 56) +#define L4_SIGN_EXT_MASK (0x1FFFFUL << 47) =20 #define LOW_ADDR (0x1UL << 30) #define HIGH_ADDR (0x3UL << 48) @@ -389,6 +398,78 @@ static int handle_syscall(struct testcases *test) return ret; } =20 +static int get_user_syscall(struct testcases *test) +{ + uint64_t ptr_address, bitmask; + int fd, ret =3D 0; + void *ptr; + + if (la57_enabled()) { + bitmask =3D L5_SIGN_EXT_MASK; + ptr_address =3D HIGH_ADDR; + } else { + bitmask =3D L4_SIGN_EXT_MASK; + ptr_address =3D LOW_ADDR; + } + + ptr =3D mmap((void *)ptr_address, PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0); + + if (ptr =3D=3D MAP_FAILED) { + perror("failed to map byte to pass into get_user"); + return 1; + } + + if (set_lam(test->lam) !=3D 0) { + ret =3D 2; + goto error; + } + + fd =3D memfd_create("lam_ioctl", 0); + if (fd =3D=3D -1) { + munmap(ptr, PAGE_SIZE); + exit(EXIT_FAILURE); + } + + switch (test->later) { + case GET_USER_USER: + /* Control group - properly tagged user pointer */ + ptr =3D (void *)set_metadata((uint64_t)ptr, test->lam); + break; + case GET_USER_KERNEL_TOP: + /* Kernel address with top bit cleared */ + bitmask &=3D (bitmask >> 1); + ptr =3D (void *)((uint64_t)ptr | bitmask); + break; + case GET_USER_KERNEL_BOT: + /* Kernel address with bottom sign-extension bit cleared */ + bitmask &=3D (bitmask << 1); + ptr =3D (void *)((uint64_t)ptr | bitmask); + break; + case GET_USER_KERNEL: + /* Try to pass a kernel address */ + ptr =3D (void *)((uint64_t)ptr | bitmask); + break; + default: + printf("Invalid test case value passed!\n"); + break; + } + + /* + * Use FIOASYNC ioctl because it utilizes get_user() internally and is + * very non-invasive to the system. Pass differently tagged pointers to + * get_user() in order to verify that valid user pointers are going + * through and invalid kernel/non-canonical pointers are not. + */ + if (ioctl(fd, FIOASYNC, ptr) !=3D 0) + ret =3D 1; + + close(fd); +error: + munmap(ptr, PAGE_SIZE); + return ret; +} + int sys_uring_setup(unsigned int entries, struct io_uring_params *p) { return (int)syscall(__NR_io_uring_setup, entries, p); @@ -902,6 +983,33 @@ static struct testcases syscall_cases[] =3D { .test_func =3D handle_syscall, .msg =3D "SYSCALL:[Negative] Disable LAM. Dereferencing pointer with met= adata.\n", }, + { + .later =3D GET_USER_USER, + .lam =3D LAM_U57_BITS, + .test_func =3D get_user_syscall, + .msg =3D "GET_USER: get_user() and pass a properly tagged user pointer.\= n", + }, + { + .later =3D GET_USER_KERNEL_TOP, + .expected =3D 1, + .lam =3D LAM_U57_BITS, + .test_func =3D get_user_syscall, + .msg =3D "GET_USER:[Negative] get_user() with a kernel pointer and the t= op bit cleared.\n", + }, + { + .later =3D GET_USER_KERNEL_BOT, + .expected =3D 1, + .lam =3D LAM_U57_BITS, + .test_func =3D get_user_syscall, + .msg =3D "GET_USER:[Negative] get_user() with a kernel pointer and the b= ottom sign-extension bit cleared.\n", + }, + { + .later =3D GET_USER_KERNEL, + .expected =3D 1, + .lam =3D LAM_U57_BITS, + .test_func =3D get_user_syscall, + .msg =3D "GET_USER:[Negative] get_user() and pass a kernel pointer.\n", + }, }; =20 static struct testcases mmap_cases[] =3D { --=20 2.47.1