From nobody Wed Feb 11 06:29:47 2026 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 38C4CC76196 for ; Fri, 31 Mar 2023 23:50:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233308AbjCaXuz (ORCPT ); Fri, 31 Mar 2023 19:50:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233175AbjCaXuu (ORCPT ); Fri, 31 Mar 2023 19:50:50 -0400 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F24B71C1E8 for ; Fri, 31 Mar 2023 16:50:48 -0700 (PDT) Received: by mail-pj1-x104a.google.com with SMTP id pt5-20020a17090b3d0500b0023d3ffe542fso5201679pjb.0 for ; Fri, 31 Mar 2023 16:50:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680306648; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=67aN/B+WtOaSUEhiQW5ieKe9kdphJ9yXXZLhFTmAYCY=; b=aqbsmcr2pK1zJc/QddLocmFe7u0eN9wv3vYw/b6U0d43YucmpKQusaaQyAaVSa0brL LpSKYapJtGiMflg5mvZkz3d5j4vniDYYeKTW9Q4ay1SgV2A+IZ22Cf6Rxm/yGJKvgMN8 SMKUd9my6zvqI6T79WbKu7yBu6efMqRgxeGWTlGD4T7pNs+f8J8J0byx5Zn/rGxIBacK RO2pdC/oG+kndVLe0/EN60h+Ufhb6JX9aJrTNcBTxw5DYOj8yvfJ2FTBeGdPqfrf3kJN vw3lhr7RqWCr8GoHdH9B4JRBqn6YLWfmu0XgDDbuD1vuUAihW3PD1pSNBYYD+O6dlOsv bwXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680306648; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=67aN/B+WtOaSUEhiQW5ieKe9kdphJ9yXXZLhFTmAYCY=; b=RkYg7ylOzYoEhH/87escTKgzVIB/GyQoV72cPtCVsUd5nAZ9ff5iMMBb8W9/uybaG8 M5Ahq4O1OtbWPLhGVbohWrYD7RhjTXXYCANUp6Im8QWShkDs6xFXMUAPMYeRQDAf2lQx CDXG+miCnh9H80dogr71gfjwPLh8o4Yop2gDSHthlL0wbkvevu7ub4RCdn5TO+bnlYRa e6be66FzPYMPBuPCD2cya9JPIRS3crBe5nkqkiPseq8jpERjpmUk0Y5cujEu1aw7B8lb kzfXYC1zeVRKk39mQEC/N+hKw/b4SvzrE8RjQni7A+2dLaYOTKTRcRcyKq1ECjpalUdk E6Rg== X-Gm-Message-State: AAQBX9ekTVTI5vhTaSrj8OnIB7hkNRN8bxlcFpbrOWeuQNxGzV3VHLgF Ykn1UTGe+JAbqCU2/jrKfttsI92qsxdcpwKXPw== X-Google-Smtp-Source: AKy350Y16oanl4juVqg+eyN21vJExuVR4y0XGk1EcBSjqL6yTWS/45m6tpDkpZOf1psTO3M9dHBN9cOBWfihqWNDiA== X-Received: from ackerleytng-cloudtop.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:1f5f]) (user=ackerleytng job=sendgmr) by 2002:a17:90a:ba0a:b0:23f:6eff:9430 with SMTP id s10-20020a17090aba0a00b0023f6eff9430mr9066957pjr.3.1680306648452; Fri, 31 Mar 2023 16:50:48 -0700 (PDT) Date: Fri, 31 Mar 2023 23:50:39 +0000 In-Reply-To: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <592ebd9e33a906ba026d56dc68f42d691706f865.1680306489.git.ackerleytng@google.com> Subject: [RFC PATCH v3 1/2] mm: restrictedmem: Allow userspace to specify mount for memfd_restricted From: Ackerley Tng To: kvm@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, qemu-devel@nongnu.org Cc: aarcange@redhat.com, ak@linux.intel.com, akpm@linux-foundation.org, arnd@arndb.de, bfields@fieldses.org, bp@alien8.de, chao.p.peng@linux.intel.com, corbet@lwn.net, dave.hansen@intel.com, david@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, hpa@zytor.com, hughd@google.com, jlayton@kernel.org, jmattson@google.com, joro@8bytes.org, jun.nakajima@intel.com, kirill.shutemov@linux.intel.com, linmiaohe@huawei.com, luto@kernel.org, mail@maciej.szmigiero.name, mhocko@suse.com, michael.roth@amd.com, mingo@redhat.com, naoya.horiguchi@nec.com, pbonzini@redhat.com, qperret@google.com, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, steven.price@arm.com, tabba@google.com, tglx@linutronix.de, vannapurve@google.com, vbabka@suse.cz, vkuznets@redhat.com, wanpengli@tencent.com, wei.w.wang@intel.com, x86@kernel.org, yu.c.zhang@linux.intel.com, Ackerley Tng Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" By default, the backing shmem file for a restrictedmem fd is created on shmem's kernel space mount. With this patch, an optional tmpfs mount can be specified via an fd, which will be used as the mountpoint for backing the shmem file associated with a restrictedmem fd. This will help restrictedmem fds inherit the properties of the provided tmpfs mounts, for example, hugepage allocation hints, NUMA binding hints, etc. Permissions for the fd passed to memfd_restricted() is modeled after the openat() syscall, since both of these allow creation of a file upon a mount/directory. Permission to reference the mount the fd represents is checked upon fd creation by other syscalls (e.g. fsmount(), open(), or open_tree(), etc) and any process that can present memfd_restricted() with a valid fd is expected to have obtained permission to use the mount represented by the fd. This behavior is intended to parallel that of the openat() syscall. memfd_restricted() will check that the tmpfs superblock is writable, and that the mount is also writable, before attempting to create a restrictedmem file on the mount. Signed-off-by: Ackerley Tng --- include/linux/syscalls.h | 2 +- include/uapi/linux/restrictedmem.h | 8 ++++ mm/restrictedmem.c | 74 +++++++++++++++++++++++++++--- 3 files changed, 77 insertions(+), 7 deletions(-) create mode 100644 include/uapi/linux/restrictedmem.h diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index f9e9e0c820c5..a23c4c385cd3 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -1056,7 +1056,7 @@ asmlinkage long sys_memfd_secret(unsigned int flags); asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned = long len, unsigned long home_node, unsigned long flags); -asmlinkage long sys_memfd_restricted(unsigned int flags); +asmlinkage long sys_memfd_restricted(unsigned int flags, int mount_fd); /* * Architecture-specific system calls diff --git a/include/uapi/linux/restrictedmem.h b/include/uapi/linux/restri= ctedmem.h new file mode 100644 index 000000000000..22d6f2285f6d --- /dev/null +++ b/include/uapi/linux/restrictedmem.h @@ -0,0 +1,8 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_RESTRICTEDMEM_H +#define _UAPI_LINUX_RESTRICTEDMEM_H + +/* flags for memfd_restricted */ +#define RMFD_USERMNT 0x0001U + +#endif /* _UAPI_LINUX_RESTRICTEDMEM_H */ diff --git a/mm/restrictedmem.c b/mm/restrictedmem.c index c5d869d8c2d8..f7b62364a31a 100644 --- a/mm/restrictedmem.c +++ b/mm/restrictedmem.c @@ -1,11 +1,12 @@ // SPDX-License-Identifier: GPL-2.0 -#include "linux/sbitmap.h" +#include #include #include #include #include #include #include +#include #include struct restrictedmem { @@ -189,19 +190,20 @@ static struct file *restrictedmem_file_create(struct = file *memfd) return file; } -SYSCALL_DEFINE1(memfd_restricted, unsigned int, flags) +static int restrictedmem_create(struct vfsmount *mount) { struct file *file, *restricted_file; int fd, err; - if (flags) - return -EINVAL; - fd =3D get_unused_fd_flags(0); if (fd < 0) return fd; - file =3D shmem_file_setup("memfd:restrictedmem", 0, VM_NORESERVE); + if (mount) + file =3D shmem_file_setup_with_mnt(mount, "memfd:restrictedmem", 0, VM_N= ORESERVE); + else + file =3D shmem_file_setup("memfd:restrictedmem", 0, VM_NORESERVE); + if (IS_ERR(file)) { err =3D PTR_ERR(file); goto err_fd; @@ -223,6 +225,66 @@ SYSCALL_DEFINE1(memfd_restricted, unsigned int, flags) return err; } +static bool is_shmem_mount(struct vfsmount *mnt) +{ + return mnt && mnt->mnt_sb && mnt->mnt_sb->s_magic =3D=3D TMPFS_MAGIC; +} + +static bool is_mount_root(struct file *file) +{ + return file->f_path.dentry =3D=3D file->f_path.mnt->mnt_root; +} + +static int restrictedmem_create_on_user_mount(int mount_fd) +{ + int ret; + struct fd f; + struct vfsmount *mnt; + + f =3D fdget_raw(mount_fd); + if (!f.file) + return -EBADF; + + ret =3D -EINVAL; + if (!is_mount_root(f.file)) + goto out; + + mnt =3D f.file->f_path.mnt; + if (!is_shmem_mount(mnt)) + goto out; + + ret =3D file_permission(f.file, MAY_WRITE | MAY_EXEC); + if (ret) + goto out; + + ret =3D mnt_want_write(mnt); + if (unlikely(ret)) + goto out; + + ret =3D restrictedmem_create(mnt); + + mnt_drop_write(mnt); +out: + fdput(f); + + return ret; +} + +SYSCALL_DEFINE2(memfd_restricted, unsigned int, flags, int, mount_fd) +{ + if (flags & ~RMFD_USERMNT) + return -EINVAL; + + if (flags =3D=3D RMFD_USERMNT) { + if (mount_fd < 0) + return -EINVAL; + + return restrictedmem_create_on_user_mount(mount_fd); + } else { + return restrictedmem_create(NULL); + } +} + int restrictedmem_bind(struct file *file, pgoff_t start, pgoff_t end, struct restrictedmem_notifier *notifier, bool exclusive) { -- 2.40.0.348.gf938b09366-goog From nobody Wed Feb 11 06:29:47 2026 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 60F2AC77B6E for ; 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Fri, 31 Mar 2023 16:50:50 -0700 (PDT) Date: Fri, 31 Mar 2023 23:50:40 +0000 In-Reply-To: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <0061b62966d34952fb9f51235d31100df0baf450.1680306489.git.ackerleytng@google.com> Subject: [RFC PATCH v3 2/2] selftests: restrictedmem: Check hugepage-ness of shmem file backing restrictedmem fd From: Ackerley Tng To: kvm@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, qemu-devel@nongnu.org Cc: aarcange@redhat.com, ak@linux.intel.com, akpm@linux-foundation.org, arnd@arndb.de, bfields@fieldses.org, bp@alien8.de, chao.p.peng@linux.intel.com, corbet@lwn.net, dave.hansen@intel.com, david@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, hpa@zytor.com, hughd@google.com, jlayton@kernel.org, jmattson@google.com, joro@8bytes.org, jun.nakajima@intel.com, kirill.shutemov@linux.intel.com, linmiaohe@huawei.com, luto@kernel.org, mail@maciej.szmigiero.name, mhocko@suse.com, michael.roth@amd.com, mingo@redhat.com, naoya.horiguchi@nec.com, pbonzini@redhat.com, qperret@google.com, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, steven.price@arm.com, tabba@google.com, tglx@linutronix.de, vannapurve@google.com, vbabka@suse.cz, vkuznets@redhat.com, wanpengli@tencent.com, wei.w.wang@intel.com, x86@kernel.org, yu.c.zhang@linux.intel.com, Ackerley Tng Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For memfd_restricted() calls without a userspace mount, the backing file should be the shmem mount in the kernel, and the size of backing pages should be as defined by system-wide shmem configuration. If a userspace mount is provided, the size of backing pages should be as defined in the mount. Also includes negative tests for invalid inputs, including fds representing read-only superblocks/mounts. Signed-off-by: Ackerley Tng --- tools/testing/selftests/Makefile | 1 + .../selftests/restrictedmem/.gitignore | 3 + .../testing/selftests/restrictedmem/Makefile | 15 + .../testing/selftests/restrictedmem/common.c | 9 + .../testing/selftests/restrictedmem/common.h | 8 + .../restrictedmem_hugepage_test.c | 486 ++++++++++++++++++ 6 files changed, 522 insertions(+) create mode 100644 tools/testing/selftests/restrictedmem/.gitignore create mode 100644 tools/testing/selftests/restrictedmem/Makefile create mode 100644 tools/testing/selftests/restrictedmem/common.c create mode 100644 tools/testing/selftests/restrictedmem/common.h create mode 100644 tools/testing/selftests/restrictedmem/restrictedmem_hug= epage_test.c diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Mak= efile index f07aef7c592c..44078eeefb79 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -60,6 +60,7 @@ TARGETS +=3D pstore TARGETS +=3D ptrace TARGETS +=3D openat2 TARGETS +=3D resctrl +TARGETS +=3D restrictedmem TARGETS +=3D rlimits TARGETS +=3D rseq TARGETS +=3D rtc diff --git a/tools/testing/selftests/restrictedmem/.gitignore b/tools/testi= ng/selftests/restrictedmem/.gitignore new file mode 100644 index 000000000000..2581bcc8ff29 --- /dev/null +++ b/tools/testing/selftests/restrictedmem/.gitignore @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only + +restrictedmem_hugepage_test diff --git a/tools/testing/selftests/restrictedmem/Makefile b/tools/testing= /selftests/restrictedmem/Makefile new file mode 100644 index 000000000000..8e5378d20226 --- /dev/null +++ b/tools/testing/selftests/restrictedmem/Makefile @@ -0,0 +1,15 @@ +# SPDX-License-Identifier: GPL-2.0 + +CFLAGS =3D $(KHDR_INCLUDES) +CFLAGS +=3D -Wall -Wstrict-prototypes -Wuninitialized -std=3Dgnu99 + +TEST_GEN_PROGS +=3D restrictedmem_hugepage_test + +include ../lib.mk + +EXTRA_CLEAN =3D $(OUTPUT)/common.o + +$(OUTPUT)/common.o: common.c + $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@ + +$(TEST_GEN_PROGS): $(OUTPUT)/common.o diff --git a/tools/testing/selftests/restrictedmem/common.c b/tools/testing= /selftests/restrictedmem/common.c new file mode 100644 index 000000000000..03dac843404f --- /dev/null +++ b/tools/testing/selftests/restrictedmem/common.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include + +int memfd_restricted(unsigned int flags, int mount_fd) +{ + return syscall(__NR_memfd_restricted, flags, mount_fd); +} diff --git a/tools/testing/selftests/restrictedmem/common.h b/tools/testing= /selftests/restrictedmem/common.h new file mode 100644 index 000000000000..06284ed86baf --- /dev/null +++ b/tools/testing/selftests/restrictedmem/common.h @@ -0,0 +1,8 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +#ifndef SELFTESTS_RESTRICTEDMEM_COMMON_H +#define SELFTESTS_RESTRICTEDMEM_COMMON_H + +int memfd_restricted(unsigned int flags, int mount_fd); + +#endif // SELFTESTS_RESTRICTEDMEM_COMMON_H diff --git a/tools/testing/selftests/restrictedmem/restrictedmem_hugepage_t= est.c b/tools/testing/selftests/restrictedmem/restrictedmem_hugepage_test.c new file mode 100644 index 000000000000..9ed319b83cb8 --- /dev/null +++ b/tools/testing/selftests/restrictedmem/restrictedmem_hugepage_test.c @@ -0,0 +1,486 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#define _GNU_SOURCE /* for O_PATH */ +#define _POSIX_C_SOURCE /* for PATH_MAX */ +#include +#include +#include +#include +#include +#include +#include + +#include "linux/restrictedmem.h" + +#include "common.h" +#include "../kselftest_harness.h" + +/* + * Expect policy to be one of always, within_size, advise, never, + * deny, force + */ +#define POLICY_BUF_SIZE 12 + +static int get_hpage_pmd_size(void) +{ + FILE *fp; + char buf[100]; + char *ret; + int size; + + fp =3D fopen("/sys/kernel/mm/transparent_hugepage/hpage_pmd_size", "r"); + if (!fp) + return -1; + + ret =3D fgets(buf, 100, fp); + if (ret !=3D buf) { + size =3D -1; + goto out; + } + + if (sscanf(buf, "%d\n", &size) !=3D 1) + size =3D -1; + +out: + fclose(fp); + + return size; +} + +static bool is_valid_shmem_thp_policy(char *policy) +{ + if (strcmp(policy, "always") =3D=3D 0) + return true; + if (strcmp(policy, "within_size") =3D=3D 0) + return true; + if (strcmp(policy, "advise") =3D=3D 0) + return true; + if (strcmp(policy, "never") =3D=3D 0) + return true; + if (strcmp(policy, "deny") =3D=3D 0) + return true; + if (strcmp(policy, "force") =3D=3D 0) + return true; + + return false; +} + +static int get_shmem_thp_policy(char *policy) +{ + FILE *fp; + char buf[100]; + char *left =3D NULL; + char *right =3D NULL; + int ret =3D -1; + + fp =3D fopen("/sys/kernel/mm/transparent_hugepage/shmem_enabled", "r"); + if (!fp) + return -1; + + if (fgets(buf, 100, fp) !=3D buf) + goto out; + + /* + * Expect shmem_enabled to be of format like "always within_size advise + * [never] deny force" + */ + left =3D memchr(buf, '[', 100); + if (!left) + goto out; + + right =3D memchr(buf, ']', 100); + if (!right) + goto out; + + memcpy(policy, left + 1, right - left - 1); + + ret =3D !is_valid_shmem_thp_policy(policy); + +out: + fclose(fp); + return ret; +} + +static int write_string_to_file(const char *path, const char *string) +{ + FILE *fp; + size_t len =3D strlen(string); + int ret =3D -1; + + fp =3D fopen(path, "w"); + if (!fp) + return ret; + + if (fwrite(string, 1, len, fp) !=3D len) + goto out; + + ret =3D 0; + +out: + fclose(fp); + return ret; +} + +static int set_shmem_thp_policy(char *policy) +{ + int ret =3D -1; + /* +1 for newline */ + char to_write[POLICY_BUF_SIZE + 1] =3D { 0 }; + + if (!is_valid_shmem_thp_policy(policy)) + return ret; + + ret =3D snprintf(to_write, POLICY_BUF_SIZE + 1, "%s\n", policy); + if (ret !=3D strlen(policy) + 1) + return -1; + + ret =3D write_string_to_file( + "/sys/kernel/mm/transparent_hugepage/shmem_enabled", to_write); + + return ret; +} + +FIXTURE(reset_shmem_enabled) +{ + char shmem_enabled[POLICY_BUF_SIZE]; +}; + +FIXTURE_SETUP(reset_shmem_enabled) +{ + memset(self->shmem_enabled, 0, POLICY_BUF_SIZE); + ASSERT_EQ(get_shmem_thp_policy(self->shmem_enabled), 0); +} + +FIXTURE_TEARDOWN(reset_shmem_enabled) +{ + ASSERT_EQ(set_shmem_thp_policy(self->shmem_enabled), 0); +} + +TEST_F(reset_shmem_enabled, restrictedmem_fstat_shmem_enabled_never) +{ + int fd =3D -1; + struct stat stat; + + ASSERT_EQ(set_shmem_thp_policy("never"), 0); + + fd =3D memfd_restricted(0, -1); + ASSERT_GT(fd, 0); + + ASSERT_EQ(fstat(fd, &stat), 0); + + /* + * st_blksize is set based on the superblock's s_blocksize_bits. For + * shmem, this is set to PAGE_SHIFT + */ + ASSERT_EQ(stat.st_blksize, getpagesize()); + + close(fd); +} + +TEST_F(reset_shmem_enabled, restrictedmem_fstat_shmem_enabled_always) +{ + int fd =3D -1; + struct stat stat; + + ASSERT_EQ(set_shmem_thp_policy("always"), 0); + + fd =3D memfd_restricted(0, -1); + ASSERT_GT(fd, 0); + + ASSERT_EQ(fstat(fd, &stat), 0); + + ASSERT_EQ(stat.st_blksize, get_hpage_pmd_size()); + + close(fd); +} + +TEST(restrictedmem_tmpfile_invalid_fd) +{ + int fd =3D memfd_restricted(RMFD_USERMNT, -2); + + ASSERT_EQ(fd, -1); + ASSERT_EQ(errno, EINVAL); +} + +TEST(restrictedmem_tmpfile_fd_not_a_mount) +{ + int fd =3D memfd_restricted(RMFD_USERMNT, STDOUT_FILENO); + + ASSERT_EQ(fd, -1); + ASSERT_EQ(errno, EINVAL); +} + +TEST(restrictedmem_tmpfile_not_tmpfs_mount) +{ + int fd =3D -1; + int mfd =3D -1; + + mfd =3D open("/proc", O_PATH); + ASSERT_NE(mfd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, mfd); + + ASSERT_EQ(fd, -1); + ASSERT_EQ(errno, EINVAL); +} + +FIXTURE(tmpfs_hugepage_sfd) +{ + int sfd; +}; + +FIXTURE_SETUP(tmpfs_hugepage_sfd) +{ + self->sfd =3D fsopen("tmpfs", 0); + ASSERT_NE(self->sfd, -1); +} + +FIXTURE_TEARDOWN(tmpfs_hugepage_sfd) +{ + EXPECT_EQ(close(self->sfd), 0); +} + +TEST_F(tmpfs_hugepage_sfd, restrictedmem_fstat_tmpfs_huge_always) +{ + int ret =3D -1; + int fd =3D -1; + int mfd =3D -1; + struct stat stat; + + fsconfig(self->sfd, FSCONFIG_SET_STRING, "huge", "always", 0); + fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); + + mfd =3D fsmount(self->sfd, 0, 0); + ASSERT_NE(mfd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, mfd); + ASSERT_GT(fd, 0); + + /* User can close reference to mount */ + ret =3D close(mfd); + ASSERT_EQ(ret, 0); + + ret =3D fstat(fd, &stat); + ASSERT_EQ(ret, 0); + ASSERT_EQ(stat.st_blksize, get_hpage_pmd_size()); + + close(fd); +} + +TEST_F(tmpfs_hugepage_sfd, restrictedmem_fstat_tmpfs_huge_never) +{ + int ret =3D -1; + int fd =3D -1; + int mfd =3D -1; + struct stat stat; + + fsconfig(self->sfd, FSCONFIG_SET_STRING, "huge", "never", 0); + fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); + + mfd =3D fsmount(self->sfd, 0, 0); + ASSERT_NE(mfd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, mfd); + ASSERT_GT(fd, 0); + + /* User can close reference to mount */ + ret =3D close(mfd); + ASSERT_EQ(ret, 0); + + ret =3D fstat(fd, &stat); + ASSERT_EQ(ret, 0); + ASSERT_EQ(stat.st_blksize, getpagesize()); + + close(fd); +} + +TEST_F(tmpfs_hugepage_sfd, restrictedmem_check_mount_flags) +{ + int ret =3D -1; + int fd =3D -1; + int mfd =3D -1; + + fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); + + mfd =3D fsmount(self->sfd, 0, MOUNT_ATTR_RDONLY); + ASSERT_NE(mfd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, mfd); + ASSERT_EQ(fd, -1); + ASSERT_EQ(errno, EROFS); + + ret =3D close(mfd); + ASSERT_EQ(ret, 0); +} + +TEST_F(tmpfs_hugepage_sfd, restrictedmem_check_superblock_flags) +{ + int ret =3D -1; + int fd =3D -1; + int mfd =3D -1; + + fsconfig(self->sfd, FSCONFIG_SET_FLAG, "ro", NULL, 0); + fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); + + mfd =3D fsmount(self->sfd, 0, 0); + ASSERT_NE(mfd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, mfd); + ASSERT_EQ(fd, -1); + ASSERT_EQ(errno, EROFS); + + ret =3D close(mfd); + ASSERT_EQ(ret, 0); +} + +static bool directory_exists(const char *path) +{ + struct stat sb; + + return stat(path, &sb) =3D=3D 0 && S_ISDIR(sb.st_mode); +} + +FIXTURE(tmpfs_hugepage_mount_path) +{ + char *mount_path; +}; + +FIXTURE_SETUP(tmpfs_hugepage_mount_path) +{ + int ret =3D -1; + + /* /tmp is an FHS-mandated world-writable directory */ + self->mount_path =3D "/tmp/restrictedmem-selftest-mnt"; + + if (!directory_exists(self->mount_path)) { + ret =3D mkdir(self->mount_path, 0777); + ASSERT_EQ(ret, 0); + } +} + +FIXTURE_TEARDOWN(tmpfs_hugepage_mount_path) +{ + int ret =3D -1; + + if (!directory_exists(self->mount_path)) + return; + + ret =3D umount2(self->mount_path, MNT_FORCE); + EXPECT_EQ(ret, 0); + if (ret =3D=3D -1 && errno =3D=3D EINVAL) + fprintf(stderr, " %s was not mounted\n", self->mount_path); + + ret =3D rmdir(self->mount_path); + EXPECT_EQ(ret, 0); + if (ret =3D=3D -1) + fprintf(stderr, " rmdir(%s) failed: %m\n", self->mount_path); +} + +/* + * memfd_restricted() syscall can only be used with the fd of the root of = the + * mount. When the restrictedmem's fd is open, a user should not be able to + * unmount or remove the mounted directory + */ +TEST_F(tmpfs_hugepage_mount_path, restrictedmem_umount_rmdir_while_file_op= en) +{ + int ret =3D -1; + int fd =3D -1; + int mfd =3D -1; + struct stat stat; + + ret =3D mount("name", self->mount_path, "tmpfs", 0, "huge=3Dalways"); + ASSERT_EQ(ret, 0); + + mfd =3D open(self->mount_path, O_PATH); + ASSERT_NE(mfd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, mfd); + ASSERT_GT(fd, 0); + + /* We don't need this reference to the mount anymore */ + ret =3D close(mfd); + ASSERT_EQ(ret, 0); + + /* restrictedmem's fd should still be usable */ + ret =3D fstat(fd, &stat); + ASSERT_EQ(ret, 0); + ASSERT_EQ(stat.st_blksize, get_hpage_pmd_size()); + + /* User should not be able to unmount directory */ + ret =3D umount2(self->mount_path, MNT_FORCE); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EBUSY); + + ret =3D rmdir(self->mount_path); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EBUSY); + + close(fd); +} + +/* The fd of a file on the mount cannot be provided as mount_fd */ +TEST_F(tmpfs_hugepage_mount_path, restrictedmem_provide_fd_of_file) +{ + int ret =3D -1; + int fd =3D -1; + int ffd =3D -1; + char tmp_file_path[PATH_MAX] =3D { 0 }; + + ret =3D mount("name", self->mount_path, "tmpfs", 0, "huge=3Dalways"); + ASSERT_EQ(ret, 0); + + snprintf(tmp_file_path, PATH_MAX, "%s/tmp-file", self->mount_path); + ret =3D write_string_to_file(tmp_file_path, "filler\n"); + ASSERT_EQ(ret, 0); + + ffd =3D open(tmp_file_path, O_RDWR); + ASSERT_GT(ffd, 0); + + fd =3D memfd_restricted(RMFD_USERMNT, ffd); + ASSERT_LT(fd, 0); + ASSERT_EQ(errno, EINVAL); + + ret =3D close(ffd); + ASSERT_EQ(ret, 0); + + close(fd); + remove(tmp_file_path); +} + +/* The fd of files on the mount cannot be provided as mount_fd */ +TEST_F(tmpfs_hugepage_mount_path, restrictedmem_provide_fd_of_file_in_subd= ir) +{ + int ret =3D -1; + int fd =3D -1; + int ffd =3D -1; + char tmp_dir_path[PATH_MAX] =3D { 0 }; + char tmp_file_path[PATH_MAX] =3D { 0 }; + + ret =3D mount("name", self->mount_path, "tmpfs", 0, "huge=3Dalways"); + ASSERT_EQ(ret, 0); + + snprintf(tmp_dir_path, PATH_MAX, "%s/tmp-subdir", self->mount_path); + ret =3D mkdir(tmp_dir_path, 0777); + ASSERT_EQ(ret, 0); + + snprintf(tmp_file_path, PATH_MAX, "%s/tmp-subdir/tmp-file", + self->mount_path); + ret =3D write_string_to_file(tmp_file_path, "filler\n"); + ASSERT_EQ(ret, 0); + + ffd =3D open(tmp_file_path, O_RDWR); + ASSERT_NE(ffd, -1); + + fd =3D memfd_restricted(RMFD_USERMNT, ffd); + ASSERT_LT(fd, 0); + ASSERT_EQ(errno, EINVAL); + + ret =3D close(ffd); + ASSERT_EQ(ret, 0); + + close(fd); + remove(tmp_file_path); + rmdir(tmp_dir_path); +} + +TEST_HARNESS_MAIN --=20 2.40.0.348.gf938b09366-goog