* [RFC PATCH v4 1/2] mm: restrictedmem: Allow userspace to specify mount for memfd_restricted
2023-04-11 1:29 [RFC PATCH v4 0/2] Providing mount in memfd_restricted() syscall Ackerley Tng
@ 2023-04-11 1:29 ` Ackerley Tng
2023-04-11 1:29 ` [RFC PATCH v4 2/2] selftests: restrictedmem: Check memfd_restricted()'s handling of provided userspace mount Ackerley Tng
1 sibling, 0 replies; 3+ messages in thread
From: Ackerley Tng @ 2023-04-11 1:29 UTC (permalink / raw)
To: kvm, linux-api, linux-arch, linux-doc, linux-fsdevel,
linux-kernel, linux-mm, qemu-devel
Cc: aarcange, ak, akpm, arnd, bfields, bp, chao.p.peng, corbet,
dave.hansen, david, ddutile, dhildenb, hpa, hughd, jlayton,
jmattson, joro, jun.nakajima, kirill.shutemov, linmiaohe, luto,
mail, mhocko, michael.roth, mingo, naoya.horiguchi, pbonzini,
qperret, rppt, seanjc, shuah, steven.price, tabba, tglx,
vannapurve, vbabka, vkuznets, wanpengli, wei.w.wang, x86,
yu.c.zhang, Ackerley Tng
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 (THP) 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 <ackerleytng@google.com>
---
include/linux/syscalls.h | 2 +-
include/uapi/linux/restrictedmem.h | 8 ++++
mm/restrictedmem.c | 73 ++++++++++++++++++++++++++++--
3 files changed, 77 insertions(+), 6 deletions(-)
create mode 100644 include/uapi/linux/restrictedmem.h
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 660be0bf89d5..90c73b9e14e5 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1058,7 +1058,7 @@ 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/restrictedmem.h
new file mode 100644
index 000000000000..73e31bce73dc
--- /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 MEMFD_RSTD_USERMNT 0x0001U
+
+#endif /* _UAPI_LINUX_RESTRICTEDMEM_H */
diff --git a/mm/restrictedmem.c b/mm/restrictedmem.c
index 55e99e6c09a1..032ad1f15138 100644
--- a/mm/restrictedmem.c
+++ b/mm/restrictedmem.c
@@ -6,6 +6,7 @@
#include <linux/syscalls.h>
#include <uapi/linux/falloc.h>
#include <uapi/linux/magic.h>
+#include <uapi/linux/restrictedmem.h>
#include <linux/restrictedmem.h>
struct restrictedmem {
@@ -250,19 +251,20 @@ static struct address_space_operations restricted_aops = {
#endif
};
-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 = get_unused_fd_flags(0);
if (fd < 0)
return fd;
- file = shmem_file_setup("memfd:restrictedmem", 0, VM_NORESERVE);
+ if (mount)
+ file = shmem_file_setup_with_mnt(mount, "memfd:restrictedmem", 0, VM_NORESERVE);
+ else
+ file = shmem_file_setup("memfd:restrictedmem", 0, VM_NORESERVE);
+
if (IS_ERR(file)) {
err = PTR_ERR(file);
goto err_fd;
@@ -286,6 +288,67 @@ SYSCALL_DEFINE1(memfd_restricted, unsigned int, flags)
return err;
}
+static struct vfsmount *restrictedmem_get_user_mount(struct file *file)
+{
+ int ret;
+ struct vfsmount *mnt;
+ struct path *path;
+
+ path = &file->f_path;
+ if (path->dentry != path->mnt->mnt_root)
+ return ERR_PTR(-EINVAL);
+
+ /*
+ * Disallow bind-mounts that aren't bind-mounts of the whole
+ * filesystem
+ */
+ mnt = path->mnt;
+ if (mnt->mnt_root != mnt->mnt_sb->s_root)
+ return ERR_PTR(-EINVAL);
+
+ if (mnt->mnt_sb->s_magic != TMPFS_MAGIC)
+ return ERR_PTR(-EINVAL);
+
+ ret = mnt_want_write(mnt);
+ if (ret)
+ return ERR_PTR(ret);
+
+ return mnt;
+}
+
+SYSCALL_DEFINE2(memfd_restricted, unsigned int, flags, int, mount_fd)
+{
+ int ret;
+ struct fd f = {};
+ struct vfsmount *mnt = NULL;
+
+ if (flags & ~MEMFD_RSTD_USERMNT)
+ return -EINVAL;
+
+ if (flags & MEMFD_RSTD_USERMNT) {
+ f = fdget_raw(mount_fd);
+ if (!f.file)
+ return -EBADF;
+
+ mnt = restrictedmem_get_user_mount(f.file);
+ if (IS_ERR(mnt)) {
+ ret = PTR_ERR(mnt);
+ goto out;
+ }
+ }
+
+ ret = restrictedmem_create(mnt);
+
+ if (mnt)
+ mnt_drop_write(mnt);
+
+out:
+ if (f.file)
+ fdput(f);
+
+ return ret;
+}
+
int restrictedmem_bind(struct file *file, pgoff_t start, pgoff_t end,
struct restrictedmem_notifier *notifier, bool exclusive)
{
--
2.40.0.577.gac1e443424-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread* [RFC PATCH v4 2/2] selftests: restrictedmem: Check memfd_restricted()'s handling of provided userspace mount
2023-04-11 1:29 [RFC PATCH v4 0/2] Providing mount in memfd_restricted() syscall Ackerley Tng
2023-04-11 1:29 ` [RFC PATCH v4 1/2] mm: restrictedmem: Allow userspace to specify mount for memfd_restricted Ackerley Tng
@ 2023-04-11 1:29 ` Ackerley Tng
1 sibling, 0 replies; 3+ messages in thread
From: Ackerley Tng @ 2023-04-11 1:29 UTC (permalink / raw)
To: kvm, linux-api, linux-arch, linux-doc, linux-fsdevel,
linux-kernel, linux-mm, qemu-devel
Cc: aarcange, ak, akpm, arnd, bfields, bp, chao.p.peng, corbet,
dave.hansen, david, ddutile, dhildenb, hpa, hughd, jlayton,
jmattson, joro, jun.nakajima, kirill.shutemov, linmiaohe, luto,
mail, mhocko, michael.roth, mingo, naoya.horiguchi, pbonzini,
qperret, rppt, seanjc, shuah, steven.price, tabba, tglx,
vannapurve, vbabka, vkuznets, wanpengli, wei.w.wang, x86,
yu.c.zhang, Ackerley Tng
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 <ackerleytng@google.com>
---
tools/testing/selftests/mm/.gitignore | 1 +
tools/testing/selftests/mm/Makefile | 1 +
.../selftests/mm/memfd_restricted_usermnt.c | 529 ++++++++++++++++++
tools/testing/selftests/mm/run_vmtests.sh | 3 +
4 files changed, 534 insertions(+)
create mode 100644 tools/testing/selftests/mm/memfd_restricted_usermnt.c
diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore
index fb6e4233374d..dba320c8151a 100644
--- a/tools/testing/selftests/mm/.gitignore
+++ b/tools/testing/selftests/mm/.gitignore
@@ -31,6 +31,7 @@ map_fixed_noreplace
write_to_hugetlbfs
hmm-tests
memfd_restricted
+memfd_restricted_usermnt
memfd_secret
soft-dirty
split_huge_page_test
diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index 5ec338ea1fed..2f5df7a12ea5 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -46,6 +46,7 @@ TEST_GEN_FILES += map_fixed_noreplace
TEST_GEN_FILES += map_hugetlb
TEST_GEN_FILES += map_populate
TEST_GEN_FILES += memfd_restricted
+TEST_GEN_FILES += memfd_restricted_usermnt
TEST_GEN_FILES += memfd_secret
TEST_GEN_FILES += migration
TEST_GEN_FILES += mlock-random-test
diff --git a/tools/testing/selftests/mm/memfd_restricted_usermnt.c b/tools/testing/selftests/mm/memfd_restricted_usermnt.c
new file mode 100644
index 000000000000..0be04e3d714d
--- /dev/null
+++ b/tools/testing/selftests/mm/memfd_restricted_usermnt.c
@@ -0,0 +1,529 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define _GNU_SOURCE /* for O_PATH */
+#define _POSIX_C_SOURCE /* for PATH_MAX */
+#include <limits.h>
+#include <sys/syscall.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+
+#include "linux/restrictedmem.h"
+
+#include "../kselftest_harness.h"
+
+static int memfd_restricted(unsigned int flags, int fd)
+{
+ return syscall(__NR_memfd_restricted, flags, fd);
+}
+
+static int get_hpage_pmd_size(void)
+{
+ FILE *fp;
+ char buf[100];
+ char *ret;
+ int size;
+
+ fp = fopen("/sys/kernel/mm/transparent_hugepage/hpage_pmd_size", "r");
+ if (!fp)
+ return -1;
+
+ ret = fgets(buf, 100, fp);
+ if (ret != buf) {
+ size = -1;
+ goto out;
+ }
+
+ if (sscanf(buf, "%d\n", &size) != 1)
+ size = -1;
+
+out:
+ fclose(fp);
+
+ return size;
+}
+
+static int write_string_to_file(const char *path, const char *string)
+{
+ FILE *fp;
+ size_t len = strlen(string);
+ int ret = -1;
+
+ fp = fopen(path, "w");
+ if (!fp)
+ return ret;
+
+ if (fwrite(string, 1, len, fp) != len)
+ goto out;
+
+ ret = 0;
+
+out:
+ fclose(fp);
+ return ret;
+}
+
+/*
+ * Expect shmem thp policy to be one of always, within_size, advise, never,
+ * deny, force
+ */
+#define POLICY_BUF_SIZE 12
+
+static bool is_valid_shmem_thp_policy(char *policy)
+{
+ if (strcmp(policy, "always") == 0)
+ return true;
+ if (strcmp(policy, "within_size") == 0)
+ return true;
+ if (strcmp(policy, "advise") == 0)
+ return true;
+ if (strcmp(policy, "never") == 0)
+ return true;
+ if (strcmp(policy, "deny") == 0)
+ return true;
+ if (strcmp(policy, "force") == 0)
+ return true;
+
+ return false;
+}
+
+static int get_shmem_thp_policy(char *policy)
+{
+ FILE *fp;
+ char buf[100];
+ char *left = NULL;
+ char *right = NULL;
+ int ret = -1;
+
+ fp = fopen("/sys/kernel/mm/transparent_hugepage/shmem_enabled", "r");
+ if (!fp)
+ return -1;
+
+ if (fgets(buf, 100, fp) != buf)
+ goto out;
+
+ /*
+ * Expect shmem_enabled to be of format like "always within_size advise
+ * [never] deny force"
+ */
+ left = memchr(buf, '[', 100);
+ if (!left)
+ goto out;
+
+ right = memchr(buf, ']', 100);
+ if (!right)
+ goto out;
+
+ memcpy(policy, left + 1, right - left - 1);
+
+ ret = !is_valid_shmem_thp_policy(policy);
+
+out:
+ fclose(fp);
+ return ret;
+}
+
+static int set_shmem_thp_policy(char *policy)
+{
+ int ret = -1;
+ /* +1 for newline */
+ char to_write[POLICY_BUF_SIZE + 1] = { 0 };
+
+ if (!is_valid_shmem_thp_policy(policy))
+ return ret;
+
+ ret = snprintf(to_write, POLICY_BUF_SIZE + 1, "%s\n", policy);
+ if (ret != strlen(policy) + 1)
+ return -1;
+
+ ret = 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 = -1;
+ struct stat stat;
+
+ ASSERT_EQ(set_shmem_thp_policy("never"), 0);
+
+ fd = 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 = -1;
+ struct stat stat;
+
+ ASSERT_EQ(set_shmem_thp_policy("always"), 0);
+
+ fd = 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 = memfd_restricted(MEMFD_RSTD_USERMNT, -2);
+
+ ASSERT_EQ(fd, -1);
+ ASSERT_EQ(errno, EBADF);
+}
+
+TEST(restrictedmem_tmpfile_fd_not_a_mount)
+{
+ int fd = memfd_restricted(MEMFD_RSTD_USERMNT, STDOUT_FILENO);
+
+ ASSERT_EQ(fd, -1);
+ ASSERT_EQ(errno, EINVAL);
+}
+
+TEST(restrictedmem_tmpfile_not_tmpfs_mount)
+{
+ int fd = -1;
+ int mfd = -1;
+
+ mfd = open("/proc", O_PATH);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+
+ ASSERT_EQ(fd, -1);
+ ASSERT_EQ(errno, EINVAL);
+}
+
+FIXTURE(tmpfs_sfd)
+{
+ int sfd;
+};
+
+FIXTURE_SETUP(tmpfs_sfd)
+{
+ self->sfd = fsopen("tmpfs", 0);
+ ASSERT_NE(self->sfd, -1);
+}
+
+FIXTURE_TEARDOWN(tmpfs_sfd)
+{
+ EXPECT_EQ(close(self->sfd), 0);
+}
+
+TEST_F(tmpfs_sfd, restrictedmem_fstat_tmpfs_huge_always)
+{
+ int ret = -1;
+ int fd = -1;
+ int mfd = -1;
+ struct stat stat;
+
+ fsconfig(self->sfd, FSCONFIG_SET_STRING, "huge", "always", 0);
+ fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
+
+ mfd = fsmount(self->sfd, 0, 0);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+ ASSERT_GT(fd, 0);
+
+ /* User can close reference to mount */
+ ret = close(mfd);
+ ASSERT_EQ(ret, 0);
+
+ ret = fstat(fd, &stat);
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(stat.st_blksize, get_hpage_pmd_size());
+
+ close(fd);
+}
+
+TEST_F(tmpfs_sfd, restrictedmem_fstat_tmpfs_huge_never)
+{
+ int ret = -1;
+ int fd = -1;
+ int mfd = -1;
+ struct stat stat;
+
+ fsconfig(self->sfd, FSCONFIG_SET_STRING, "huge", "never", 0);
+ fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
+
+ mfd = fsmount(self->sfd, 0, 0);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+ ASSERT_GT(fd, 0);
+
+ /* User can close reference to mount */
+ ret = close(mfd);
+ ASSERT_EQ(ret, 0);
+
+ ret = fstat(fd, &stat);
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(stat.st_blksize, getpagesize());
+
+ close(fd);
+}
+
+TEST_F(tmpfs_sfd, restrictedmem_check_mount_flags)
+{
+ int ret = -1;
+ int fd = -1;
+ int mfd = -1;
+
+ fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
+
+ mfd = fsmount(self->sfd, 0, MOUNT_ATTR_RDONLY);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+ ASSERT_EQ(fd, -1);
+ ASSERT_EQ(errno, EROFS);
+
+ ret = close(mfd);
+ ASSERT_EQ(ret, 0);
+}
+
+TEST_F(tmpfs_sfd, restrictedmem_check_superblock_flags)
+{
+ int ret = -1;
+ int fd = -1;
+ int mfd = -1;
+
+ fsconfig(self->sfd, FSCONFIG_SET_FLAG, "ro", NULL, 0);
+ fsconfig(self->sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
+
+ mfd = fsmount(self->sfd, 0, 0);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+ ASSERT_EQ(fd, -1);
+ ASSERT_EQ(errno, EROFS);
+
+ ret = close(mfd);
+ ASSERT_EQ(ret, 0);
+}
+
+static bool directory_exists(const char *path)
+{
+ struct stat sb;
+
+ return stat(path, &sb) == 0 && S_ISDIR(sb.st_mode);
+}
+
+FIXTURE(restrictedmem_test_mount_path)
+{
+ char *mount_path;
+};
+
+FIXTURE_SETUP(restrictedmem_test_mount_path)
+{
+ int ret = -1;
+
+ /* /tmp is an FHS-mandated world-writable directory */
+ self->mount_path = "/tmp/restrictedmem-selftest-mnt";
+
+ if (!directory_exists(self->mount_path)) {
+ ret = mkdir(self->mount_path, 0777);
+ ASSERT_EQ(ret, 0);
+ }
+}
+
+FIXTURE_TEARDOWN(restrictedmem_test_mount_path)
+{
+ int ret = -1;
+
+ if (!directory_exists(self->mount_path))
+ return;
+
+ ret = umount2(self->mount_path, MNT_FORCE);
+ EXPECT_EQ(ret, 0);
+ if (ret == -1 && errno == EINVAL)
+ fprintf(stderr, " %s was not mounted\n", self->mount_path);
+
+ ret = rmdir(self->mount_path);
+ EXPECT_EQ(ret, 0);
+ if (ret == -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(restrictedmem_test_mount_path, restrictedmem_umount_rmdir_while_file_open)
+{
+ int ret = -1;
+ int fd = -1;
+ int mfd = -1;
+ struct stat stat;
+
+ ret = mount("name", self->mount_path, "tmpfs", 0, "huge=always");
+ ASSERT_EQ(ret, 0);
+
+ mfd = open(self->mount_path, O_PATH);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+ ASSERT_GT(fd, 0);
+
+ /* We don't need this reference to the mount anymore */
+ ret = close(mfd);
+ ASSERT_EQ(ret, 0);
+
+ /* restrictedmem's fd should still be usable */
+ ret = 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 = umount2(self->mount_path, MNT_FORCE);
+ ASSERT_EQ(ret, -1);
+ ASSERT_EQ(errno, EBUSY);
+
+ ret = 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(restrictedmem_test_mount_path, restrictedmem_provide_fd_of_file)
+{
+ int ret = -1;
+ int fd = -1;
+ int ffd = -1;
+ char tmp_file_path[PATH_MAX] = { 0 };
+
+ ret = mount("name", self->mount_path, "tmpfs", 0, "huge=always");
+ ASSERT_EQ(ret, 0);
+
+ snprintf(tmp_file_path, PATH_MAX, "%s/tmp-file", self->mount_path);
+ ret = write_string_to_file(tmp_file_path, "filler\n");
+ ASSERT_EQ(ret, 0);
+
+ ffd = open(tmp_file_path, O_RDWR);
+ ASSERT_GT(ffd, 0);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, ffd);
+ ASSERT_LT(fd, 0);
+ ASSERT_EQ(errno, EINVAL);
+
+ ret = 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(restrictedmem_test_mount_path, restrictedmem_provide_fd_of_file_in_subdir)
+{
+ int ret = -1;
+ int fd = -1;
+ int ffd = -1;
+ char tmp_dir_path[PATH_MAX] = { 0 };
+ char tmp_file_path[PATH_MAX] = { 0 };
+
+ ret = mount("name", self->mount_path, "tmpfs", 0, "huge=always");
+ ASSERT_EQ(ret, 0);
+
+ snprintf(tmp_dir_path, PATH_MAX, "%s/tmp-subdir", self->mount_path);
+ ret = mkdir(tmp_dir_path, 0777);
+ ASSERT_EQ(ret, 0);
+
+ snprintf(tmp_file_path, PATH_MAX, "%s/tmp-subdir/tmp-file",
+ self->mount_path);
+ ret = write_string_to_file(tmp_file_path, "filler\n");
+ ASSERT_EQ(ret, 0);
+
+ ffd = open(tmp_file_path, O_RDWR);
+ ASSERT_NE(ffd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, ffd);
+ ASSERT_LT(fd, 0);
+ ASSERT_EQ(errno, EINVAL);
+
+ ret = close(ffd);
+ ASSERT_EQ(ret, 0);
+
+ remove(tmp_file_path);
+ rmdir(tmp_dir_path);
+}
+
+/*
+ * fds representing bind mounts must represent the root of the original
+ * filesystem
+ */
+TEST_F(restrictedmem_test_mount_path, restrictedmem_provide_fd_of_original_fs)
+{
+ int ret = -1;
+ int fd = -1;
+ int mfd = -1;
+ char tmp_dir_path_0[PATH_MAX] = { 0 };
+ char tmp_dir_path_1[PATH_MAX] = { 0 };
+
+ ret = mount("name", self->mount_path, "tmpfs", 0, "huge=always");
+ ASSERT_EQ(ret, 0);
+
+ snprintf(tmp_dir_path_0, PATH_MAX, "%s/tmp-subdir-0", self->mount_path);
+ ret = mkdir(tmp_dir_path_0, 0777);
+ ASSERT_EQ(ret, 0);
+
+ snprintf(tmp_dir_path_1, PATH_MAX, "%s/tmp-subdir-1", self->mount_path);
+ ret = mkdir(tmp_dir_path_1, 0777);
+ ASSERT_EQ(ret, 0);
+
+ ret = mount(tmp_dir_path_0, tmp_dir_path_1, "tmpfs", MS_BIND, NULL);
+ ASSERT_EQ(ret, 0);
+
+ mfd = open(tmp_dir_path_1, O_PATH);
+ ASSERT_NE(mfd, -1);
+
+ fd = memfd_restricted(MEMFD_RSTD_USERMNT, mfd);
+ ASSERT_LT(fd, 0);
+ ASSERT_EQ(errno, EINVAL);
+
+ ret = close(mfd);
+ ASSERT_EQ(ret, 0);
+
+ ret = umount2(tmp_dir_path_1, MNT_FORCE);
+ ASSERT_EQ(ret, 0);
+
+ rmdir(tmp_dir_path_0);
+ rmdir(tmp_dir_path_1);
+}
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 53de84e3ec2c..04238f86f037 100644
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -40,6 +40,8 @@ separated by spaces:
test memadvise(2) MADV_POPULATE_{READ,WRITE} options
- memfd_restricted_
test memfd_restricted(2)
+- memfd_restricted_usermnt
+ test memfd_restricted(2)'s handling of provided userspace mounts
- memfd_secret
test memfd_secret(2)
- process_mrelease
@@ -239,6 +241,7 @@ CATEGORY="hmm" run_test ./test_hmm.sh smoke
CATEGORY="madv_populate" run_test ./madv_populate
CATEGORY="memfd_restricted" run_test ./memfd_restricted
+CATEGORY="memfd_restricted_usermnt" run_test ./memfd_restricted_usermnt
CATEGORY="memfd_secret" run_test ./memfd_secret
--
2.40.0.577.gac1e443424-goog
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