From 9b8a0ba68246a61d903ce62c35c303b1501df28b Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 29 Dec 2025 14:03:24 +0100 Subject: [PATCH 1/2] mount: add OPEN_TREE_NAMESPACE When creating containers the setup usually involves using CLONE_NEWNS via clone3() or unshare(). This copies the caller's complete mount namespace. The runtime will also assemble a new rootfs and then use pivot_root() to switch the old mount tree with the new rootfs. Afterward it will recursively umount the old mount tree thereby getting rid of all mounts. On a basic system here where the mount table isn't particularly large this still copies about 30 mounts. Copying all of these mounts only to get rid of them later is pretty wasteful. This is exacerbated if intermediary mount namespaces are used that only exist for a very short amount of time and are immediately destroyed again causing a ton of mounts to be copied and destroyed needlessly. With a large mount table and a system where thousands or ten-thousands of containers are spawned in parallel this quickly becomes a bottleneck increasing contention on the semaphore. Extend open_tree() with a new OPEN_TREE_NAMESPACE flag. Similar to OPEN_TREE_CLONE only the indicated mount tree is copied. Instead of returning a file descriptor referring to that mount tree OPEN_TREE_NAMESPACE will cause open_tree() to return a file descriptor to a new mount namespace. In that new mount namespace the copied mount tree has been mounted on top of a copy of the real rootfs. The caller can setns() into that mount namespace and perform any additionally required setup such as move_mount() detached mounts in there. This allows OPEN_TREE_NAMESPACE to function as a combined unshare(CLONE_NEWNS) and pivot_root(). A caller may for example choose to create an extremely minimal rootfs: fd_mntns = open_tree(-EBADF, "/var/lib/containers/wootwoot", OPEN_TREE_NAMESPACE); This will create a mount namespace where "wootwoot" has become the rootfs mounted on top of the real rootfs. The caller can now setns() into this new mount namespace and assemble additional mounts. This also works with user namespaces: unshare(CLONE_NEWUSER); fd_mntns = open_tree(-EBADF, "/var/lib/containers/wootwoot", OPEN_TREE_NAMESPACE); which creates a new mount namespace owned by the earlier created user namespace with "wootwoot" as the rootfs mounted on top of the real rootfs. Link: https://patch.msgid.link/20251229-work-empty-namespace-v1-1-bfb24c7b061f@kernel.org Tested-by: Jeff Layton Reviewed-by: Aleksa Sarai Reviewed-by: Jeff Layton Suggested-by: Christian Brauner Suggested-by: Aleksa Sarai Signed-off-by: Christian Brauner --- fs/internal.h | 1 + fs/namespace.c | 163 +++++++++++++++++++++++++++++++++---- fs/nsfs.c | 13 +++ include/uapi/linux/mount.h | 3 +- 4 files changed, 163 insertions(+), 17 deletions(-) diff --git a/fs/internal.h b/fs/internal.h index e333b105337a..f6932e639f36 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -246,6 +246,7 @@ extern void mnt_pin_kill(struct mount *m); */ extern const struct dentry_operations ns_dentry_operations; int open_namespace(struct ns_common *ns); +struct file *open_namespace_file(struct ns_common *ns); /* * fs/stat.c: diff --git a/fs/namespace.c b/fs/namespace.c index ec3b16fedd9f..59557019e422 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2796,6 +2796,9 @@ static inline void unlock_mount(struct pinned_mountpoint *m) __unlock_mount(m); } +static void lock_mount_exact(const struct path *path, + struct pinned_mountpoint *mp); + #define LOCK_MOUNT_MAYBE_BENEATH(mp, path, beneath) \ struct pinned_mountpoint mp __cleanup(unlock_mount) = {}; \ do_lock_mount((path), &mp, (beneath)) @@ -2946,10 +2949,11 @@ static inline bool may_copy_tree(const struct path *path) return check_anonymous_mnt(mnt); } - -static struct mount *__do_loopback(const struct path *old_path, int recurse) +static struct mount *__do_loopback(const struct path *old_path, + unsigned int flags, unsigned int copy_flags) { struct mount *old = real_mount(old_path->mnt); + bool recurse = flags & AT_RECURSIVE; if (IS_MNT_UNBINDABLE(old)) return ERR_PTR(-EINVAL); @@ -2960,10 +2964,22 @@ static struct mount *__do_loopback(const struct path *old_path, int recurse) if (!recurse && __has_locked_children(old, old_path->dentry)) return ERR_PTR(-EINVAL); + /* + * When creating a new mount namespace we don't want to copy over + * mounts of mount namespaces to avoid the risk of cycles and also to + * minimize the default complex interdependencies between mount + * namespaces. + * + * We could ofc just check whether all mount namespace files aren't + * creating cycles but really let's keep this simple. + */ + if (!(flags & OPEN_TREE_NAMESPACE)) + copy_flags |= CL_COPY_MNT_NS_FILE; + if (recurse) - return copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE); - else - return clone_mnt(old, old_path->dentry, 0); + return copy_tree(old, old_path->dentry, copy_flags); + + return clone_mnt(old, old_path->dentry, copy_flags); } /* @@ -2974,7 +2990,9 @@ static int do_loopback(const struct path *path, const char *old_name, { struct path old_path __free(path_put) = {}; struct mount *mnt = NULL; + unsigned int flags = recurse ? AT_RECURSIVE : 0; int err; + if (!old_name || !*old_name) return -EINVAL; err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); @@ -2991,7 +3009,7 @@ static int do_loopback(const struct path *path, const char *old_name, if (!check_mnt(mp.parent)) return -EINVAL; - mnt = __do_loopback(&old_path, recurse); + mnt = __do_loopback(&old_path, flags, 0); if (IS_ERR(mnt)) return PTR_ERR(mnt); @@ -3004,7 +3022,7 @@ static int do_loopback(const struct path *path, const char *old_name, return err; } -static struct mnt_namespace *get_detached_copy(const struct path *path, bool recursive) +static struct mnt_namespace *get_detached_copy(const struct path *path, unsigned int flags) { struct mnt_namespace *ns, *mnt_ns = current->nsproxy->mnt_ns, *src_mnt_ns; struct user_namespace *user_ns = mnt_ns->user_ns; @@ -3029,7 +3047,7 @@ static struct mnt_namespace *get_detached_copy(const struct path *path, bool rec ns->seq_origin = src_mnt_ns->ns.ns_id; } - mnt = __do_loopback(path, recursive); + mnt = __do_loopback(path, flags, 0); if (IS_ERR(mnt)) { emptied_ns = ns; return ERR_CAST(mnt); @@ -3043,9 +3061,9 @@ static struct mnt_namespace *get_detached_copy(const struct path *path, bool rec return ns; } -static struct file *open_detached_copy(struct path *path, bool recursive) +static struct file *open_detached_copy(struct path *path, unsigned int flags) { - struct mnt_namespace *ns = get_detached_copy(path, recursive); + struct mnt_namespace *ns = get_detached_copy(path, flags); struct file *file; if (IS_ERR(ns)) @@ -3061,21 +3079,122 @@ static struct file *open_detached_copy(struct path *path, bool recursive) return file; } +DEFINE_FREE(put_empty_mnt_ns, struct mnt_namespace *, + if (!IS_ERR_OR_NULL(_T)) free_mnt_ns(_T)) + +static struct mnt_namespace *create_new_namespace(struct path *path, unsigned int flags) +{ + struct mnt_namespace *new_ns __free(put_empty_mnt_ns) = NULL; + struct path to_path __free(path_put) = {}; + struct mnt_namespace *ns = current->nsproxy->mnt_ns; + struct user_namespace *user_ns = current_user_ns(); + struct mount *new_ns_root; + struct mount *mnt; + unsigned int copy_flags = 0; + bool locked = false; + + if (user_ns != ns->user_ns) + copy_flags |= CL_SLAVE; + + new_ns = alloc_mnt_ns(user_ns, false); + if (IS_ERR(new_ns)) + return ERR_CAST(new_ns); + + scoped_guard(namespace_excl) { + new_ns_root = clone_mnt(ns->root, ns->root->mnt.mnt_root, copy_flags); + if (IS_ERR(new_ns_root)) + return ERR_CAST(new_ns_root); + + /* + * If the real rootfs had a locked mount on top of it somewhere + * in the stack, lock the new mount tree as well so it can't be + * exposed. + */ + mnt = ns->root; + while (mnt->overmount) { + mnt = mnt->overmount; + if (mnt->mnt.mnt_flags & MNT_LOCKED) + locked = true; + } + } + + /* + * We dropped the namespace semaphore so we can actually lock + * the copy for mounting. The copied mount isn't attached to any + * mount namespace and it is thus excluded from any propagation. + * So realistically we're isolated and the mount can't be + * overmounted. + */ + + /* Borrow the reference from clone_mnt(). */ + to_path.mnt = &new_ns_root->mnt; + to_path.dentry = dget(new_ns_root->mnt.mnt_root); + + /* Now lock for actual mounting. */ + LOCK_MOUNT_EXACT(mp, &to_path); + if (unlikely(IS_ERR(mp.parent))) + return ERR_CAST(mp.parent); + + /* + * We don't emulate unshare()ing a mount namespace. We stick to the + * restrictions of creating detached bind-mounts. It has a lot + * saner and simpler semantics. + */ + mnt = __do_loopback(path, flags, copy_flags); + if (IS_ERR(mnt)) + return ERR_CAST(mnt); + + scoped_guard(mount_writer) { + if (locked) + mnt->mnt.mnt_flags |= MNT_LOCKED; + /* + * Now mount the detached tree on top of the copy of the + * real rootfs we created. + */ + attach_mnt(mnt, new_ns_root, mp.mp); + if (user_ns != ns->user_ns) + lock_mnt_tree(new_ns_root); + } + + /* Add all mounts to the new namespace. */ + for (struct mount *p = new_ns_root; p; p = next_mnt(p, new_ns_root)) { + mnt_add_to_ns(new_ns, p); + new_ns->nr_mounts++; + } + + new_ns->root = real_mount(no_free_ptr(to_path.mnt)); + ns_tree_add_raw(new_ns); + return no_free_ptr(new_ns); +} + +static struct file *open_new_namespace(struct path *path, unsigned int flags) +{ + struct mnt_namespace *new_ns; + + new_ns = create_new_namespace(path, flags); + if (IS_ERR(new_ns)) + return ERR_CAST(new_ns); + return open_namespace_file(to_ns_common(new_ns)); +} + static struct file *vfs_open_tree(int dfd, const char __user *filename, unsigned int flags) { int ret; struct path path __free(path_put) = {}; int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; - bool detached = flags & OPEN_TREE_CLONE; BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | - OPEN_TREE_CLOEXEC)) + OPEN_TREE_CLOEXEC | OPEN_TREE_NAMESPACE)) return ERR_PTR(-EINVAL); - if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE) + if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE | OPEN_TREE_NAMESPACE)) == + AT_RECURSIVE) + return ERR_PTR(-EINVAL); + + if (hweight32(flags & (OPEN_TREE_CLONE | OPEN_TREE_NAMESPACE)) > 1) return ERR_PTR(-EINVAL); if (flags & AT_NO_AUTOMOUNT) @@ -3085,15 +3204,27 @@ static struct file *vfs_open_tree(int dfd, const char __user *filename, unsigned if (flags & AT_EMPTY_PATH) lookup_flags |= LOOKUP_EMPTY; - if (detached && !may_mount()) + /* + * If we create a new mount namespace with the cloned mount tree we + * just care about being privileged over our current user namespace. + * The new mount namespace will be owned by it. + */ + if ((flags & OPEN_TREE_NAMESPACE) && + !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + return ERR_PTR(-EPERM); + + if ((flags & OPEN_TREE_CLONE) && !may_mount()) return ERR_PTR(-EPERM); ret = user_path_at(dfd, filename, lookup_flags, &path); if (unlikely(ret)) return ERR_PTR(ret); - if (detached) - return open_detached_copy(&path, flags & AT_RECURSIVE); + if (flags & OPEN_TREE_NAMESPACE) + return open_new_namespace(&path, flags); + + if (flags & OPEN_TREE_CLONE) + return open_detached_copy(&path, flags); return dentry_open(&path, O_PATH, current_cred()); } diff --git a/fs/nsfs.c b/fs/nsfs.c index bf27d5da91f1..db91de208645 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -99,6 +99,19 @@ int ns_get_path(struct path *path, struct task_struct *task, return ns_get_path_cb(path, ns_get_path_task, &args); } +struct file *open_namespace_file(struct ns_common *ns) +{ + struct path path __free(path_put) = {}; + int err; + + /* call first to consume reference */ + err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path); + if (err < 0) + return ERR_PTR(err); + + return dentry_open(&path, O_RDONLY, current_cred()); +} + /** * open_namespace - open a namespace * @ns: the namespace to open diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index 18c624405268..d9d86598d100 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -61,7 +61,8 @@ /* * open_tree() flags. */ -#define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */ +#define OPEN_TREE_CLONE (1 << 0) /* Clone the target tree and attach the clone */ +#define OPEN_TREE_NAMESPACE (1 << 1) /* Clone the target tree into a new mount namespace */ #define OPEN_TREE_CLOEXEC O_CLOEXEC /* Close the file on execve() */ /* From b8f7622aa6e32d6fd750697b99d8ce19ad8e66d0 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 29 Dec 2025 14:03:25 +0100 Subject: [PATCH 2/2] selftests/open_tree: add OPEN_TREE_NAMESPACE tests Add tests for OPEN_TREE_NAMESPACE. Link: https://patch.msgid.link/20251229-work-empty-namespace-v1-2-bfb24c7b061f@kernel.org Tested-by: Jeff Layton Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner --- .../filesystems/open_tree_ns/.gitignore | 1 + .../filesystems/open_tree_ns/Makefile | 10 + .../open_tree_ns/open_tree_ns_test.c | 1030 +++++++++++++++++ tools/testing/selftests/filesystems/utils.c | 26 + tools/testing/selftests/filesystems/utils.h | 1 + 5 files changed, 1068 insertions(+) create mode 100644 tools/testing/selftests/filesystems/open_tree_ns/.gitignore create mode 100644 tools/testing/selftests/filesystems/open_tree_ns/Makefile create mode 100644 tools/testing/selftests/filesystems/open_tree_ns/open_tree_ns_test.c diff --git a/tools/testing/selftests/filesystems/open_tree_ns/.gitignore b/tools/testing/selftests/filesystems/open_tree_ns/.gitignore new file mode 100644 index 000000000000..fb12b93fbcaa --- /dev/null +++ b/tools/testing/selftests/filesystems/open_tree_ns/.gitignore @@ -0,0 +1 @@ +open_tree_ns_test diff --git a/tools/testing/selftests/filesystems/open_tree_ns/Makefile b/tools/testing/selftests/filesystems/open_tree_ns/Makefile new file mode 100644 index 000000000000..73c03c4a7ef6 --- /dev/null +++ b/tools/testing/selftests/filesystems/open_tree_ns/Makefile @@ -0,0 +1,10 @@ +# SPDX-License-Identifier: GPL-2.0 +TEST_GEN_PROGS := open_tree_ns_test + +CFLAGS := -Wall -Werror -g $(KHDR_INCLUDES) +LDLIBS := -lcap + +include ../../lib.mk + +$(OUTPUT)/open_tree_ns_test: open_tree_ns_test.c ../utils.c + $(CC) $(CFLAGS) -o $@ $^ $(LDLIBS) diff --git a/tools/testing/selftests/filesystems/open_tree_ns/open_tree_ns_test.c b/tools/testing/selftests/filesystems/open_tree_ns/open_tree_ns_test.c new file mode 100644 index 000000000000..9711556280ae --- /dev/null +++ b/tools/testing/selftests/filesystems/open_tree_ns/open_tree_ns_test.c @@ -0,0 +1,1030 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Test for OPEN_TREE_NAMESPACE flag. + * + * Test that open_tree() with OPEN_TREE_NAMESPACE creates a new mount + * namespace containing the specified mount tree. + */ +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "../wrappers.h" +#include "../statmount/statmount.h" +#include "../utils.h" +#include "../../kselftest_harness.h" + +#ifndef OPEN_TREE_NAMESPACE +#define OPEN_TREE_NAMESPACE (1 << 1) +#endif + +static int get_mnt_ns_id(int fd, uint64_t *mnt_ns_id) +{ + if (ioctl(fd, NS_GET_MNTNS_ID, mnt_ns_id) < 0) + return -errno; + return 0; +} + +static int get_mnt_ns_id_from_path(const char *path, uint64_t *mnt_ns_id) +{ + int fd, ret; + + fd = open(path, O_RDONLY); + if (fd < 0) + return -errno; + + ret = get_mnt_ns_id(fd, mnt_ns_id); + close(fd); + return ret; +} + +#define STATMOUNT_BUFSIZE (1 << 15) + +static struct statmount *statmount_alloc(uint64_t mnt_id, uint64_t mnt_ns_id, uint64_t mask) +{ + struct statmount *buf; + size_t bufsize = STATMOUNT_BUFSIZE; + int ret; + + for (;;) { + buf = malloc(bufsize); + if (!buf) + return NULL; + + ret = statmount(mnt_id, mnt_ns_id, mask, buf, bufsize, 0); + if (ret == 0) + return buf; + + free(buf); + if (errno != EOVERFLOW) + return NULL; + + bufsize <<= 1; + } +} + +static void log_mount(struct __test_metadata *_metadata, struct statmount *sm) +{ + const char *fs_type = ""; + const char *mnt_root = ""; + const char *mnt_point = ""; + + if (sm->mask & STATMOUNT_FS_TYPE) + fs_type = sm->str + sm->fs_type; + if (sm->mask & STATMOUNT_MNT_ROOT) + mnt_root = sm->str + sm->mnt_root; + if (sm->mask & STATMOUNT_MNT_POINT) + mnt_point = sm->str + sm->mnt_point; + + TH_LOG(" mnt_id: %llu, parent_id: %llu, fs_type: %s, root: %s, point: %s", + (unsigned long long)sm->mnt_id, + (unsigned long long)sm->mnt_parent_id, + fs_type, mnt_root, mnt_point); +} + +static void dump_mounts(struct __test_metadata *_metadata, uint64_t mnt_ns_id) +{ + uint64_t list[256]; + ssize_t nr_mounts; + + nr_mounts = listmount(LSMT_ROOT, mnt_ns_id, 0, list, 256, 0); + if (nr_mounts < 0) { + TH_LOG("listmount failed: %s", strerror(errno)); + return; + } + + TH_LOG("Mount namespace %llu contains %zd mount(s):", + (unsigned long long)mnt_ns_id, nr_mounts); + + for (ssize_t i = 0; i < nr_mounts; i++) { + struct statmount *sm; + + sm = statmount_alloc(list[i], mnt_ns_id, + STATMOUNT_MNT_BASIC | + STATMOUNT_FS_TYPE | + STATMOUNT_MNT_ROOT | + STATMOUNT_MNT_POINT); + if (!sm) { + TH_LOG(" [%zd] mnt_id %llu: statmount failed: %s", + i, (unsigned long long)list[i], strerror(errno)); + continue; + } + + log_mount(_metadata, sm); + free(sm); + } +} + +FIXTURE(open_tree_ns) +{ + int fd; + uint64_t current_ns_id; +}; + +FIXTURE_VARIANT(open_tree_ns) +{ + const char *path; + unsigned int flags; + bool expect_success; + bool expect_different_ns; + int min_mounts; +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, basic_root) +{ + .path = "/", + .flags = OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC, + .expect_success = true, + .expect_different_ns = true, + /* + * The empty rootfs is hidden from listmount()/mountinfo, + * so we only see the bind mount on top of it. + */ + .min_mounts = 1, +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, recursive_root) +{ + .path = "/", + .flags = OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC, + .expect_success = true, + .expect_different_ns = true, + .min_mounts = 1, +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, subdir_tmp) +{ + .path = "/tmp", + .flags = OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC, + .expect_success = true, + .expect_different_ns = true, + .min_mounts = 1, +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, subdir_proc) +{ + .path = "/proc", + .flags = OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC, + .expect_success = true, + .expect_different_ns = true, + .min_mounts = 1, +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, recursive_tmp) +{ + .path = "/tmp", + .flags = OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC, + .expect_success = true, + .expect_different_ns = true, + .min_mounts = 1, +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, recursive_run) +{ + .path = "/run", + .flags = OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC, + .expect_success = true, + .expect_different_ns = true, + .min_mounts = 1, +}; + +FIXTURE_VARIANT_ADD(open_tree_ns, invalid_recursive_alone) +{ + .path = "/", + .flags = AT_RECURSIVE | OPEN_TREE_CLOEXEC, + .expect_success = false, + .expect_different_ns = false, + .min_mounts = 0, +}; + +FIXTURE_SETUP(open_tree_ns) +{ + int ret; + + self->fd = -1; + + /* Check if open_tree syscall is supported */ + ret = sys_open_tree(-1, NULL, 0); + if (ret == -1 && errno == ENOSYS) + SKIP(return, "open_tree() syscall not supported"); + + /* Check if statmount/listmount are supported */ + ret = statmount(0, 0, 0, NULL, 0, 0); + if (ret == -1 && errno == ENOSYS) + SKIP(return, "statmount() syscall not supported"); + + /* Get current mount namespace ID for comparison */ + ret = get_mnt_ns_id_from_path("/proc/self/ns/mnt", &self->current_ns_id); + if (ret < 0) + SKIP(return, "Failed to get current mount namespace ID"); +} + +FIXTURE_TEARDOWN(open_tree_ns) +{ + if (self->fd >= 0) + close(self->fd); +} + +TEST_F(open_tree_ns, create_namespace) +{ + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int ret; + + self->fd = sys_open_tree(AT_FDCWD, variant->path, variant->flags); + + if (!variant->expect_success) { + ASSERT_LT(self->fd, 0); + ASSERT_EQ(errno, EINVAL); + return; + } + + if (self->fd < 0 && errno == EINVAL) + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + + ASSERT_GE(self->fd, 0); + + /* Verify we can get the namespace ID */ + ret = get_mnt_ns_id(self->fd, &new_ns_id); + ASSERT_EQ(ret, 0); + + /* Verify it's a different namespace */ + if (variant->expect_different_ns) + ASSERT_NE(new_ns_id, self->current_ns_id); + + /* List mounts in the new namespace */ + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, 0); + ASSERT_GE(nr_mounts, 0) { + TH_LOG("%m - listmount failed"); + } + + /* Verify minimum expected mounts */ + ASSERT_GE(nr_mounts, variant->min_mounts); + TH_LOG("Namespace contains %zd mounts", nr_mounts); +} + +TEST_F(open_tree_ns, setns_into_namespace) +{ + uint64_t new_ns_id; + pid_t pid; + int status; + int ret; + + /* Only test with basic flags */ + if (!(variant->flags & OPEN_TREE_NAMESPACE)) + SKIP(return, "setns test only for basic / case"); + + self->fd = sys_open_tree(AT_FDCWD, variant->path, variant->flags); + if (self->fd < 0 && errno == EINVAL) + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + + ASSERT_GE(self->fd, 0); + + /* Get namespace ID and dump all mounts */ + ret = get_mnt_ns_id(self->fd, &new_ns_id); + ASSERT_EQ(ret, 0); + + dump_mounts(_metadata, new_ns_id); + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + /* Child: try to enter the namespace */ + if (setns(self->fd, CLONE_NEWNS) < 0) + _exit(1); + _exit(0); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + ASSERT_EQ(WEXITSTATUS(status), 0); +} + +TEST_F(open_tree_ns, verify_mount_properties) +{ + struct statmount sm; + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int ret; + + /* Only test with basic flags on root */ + if (variant->flags != (OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC) || + strcmp(variant->path, "/") != 0) + SKIP(return, "mount properties test only for basic / case"); + + self->fd = sys_open_tree(AT_FDCWD, "/", OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC); + if (self->fd < 0 && errno == EINVAL) + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + + ASSERT_GE(self->fd, 0); + + ret = get_mnt_ns_id(self->fd, &new_ns_id); + ASSERT_EQ(ret, 0); + + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, 0); + ASSERT_GE(nr_mounts, 1); + + /* Get info about the root mount (the bind mount, rootfs is hidden) */ + ret = statmount(list[0], new_ns_id, STATMOUNT_MNT_BASIC, &sm, sizeof(sm), 0); + ASSERT_EQ(ret, 0); + + ASSERT_NE(sm.mnt_id, sm.mnt_parent_id); + + TH_LOG("Root mount id: %llu, parent: %llu", + (unsigned long long)sm.mnt_id, + (unsigned long long)sm.mnt_parent_id); +} + +FIXTURE(open_tree_ns_caps) +{ + bool has_caps; +}; + +FIXTURE_SETUP(open_tree_ns_caps) +{ + int ret; + + /* Check if open_tree syscall is supported */ + ret = sys_open_tree(-1, NULL, 0); + if (ret == -1 && errno == ENOSYS) + SKIP(return, "open_tree() syscall not supported"); + + self->has_caps = (geteuid() == 0); +} + +FIXTURE_TEARDOWN(open_tree_ns_caps) +{ +} + +TEST_F(open_tree_ns_caps, requires_cap_sys_admin) +{ + pid_t pid; + int status; + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + int fd; + + /* Child: drop privileges using utils.h helper */ + if (enter_userns() != 0) + _exit(2); + + /* Drop all caps using utils.h helper */ + if (caps_down() == 0) + _exit(3); + + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC); + if (fd >= 0) { + close(fd); + /* Should have failed without caps */ + _exit(1); + } + + if (errno == EPERM) + _exit(0); + + /* EINVAL means OPEN_TREE_NAMESPACE not supported */ + if (errno == EINVAL) + _exit(4); + + /* Unexpected error */ + _exit(5); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + + switch (WEXITSTATUS(status)) { + case 0: + /* Expected: EPERM without caps */ + break; + case 1: + ASSERT_FALSE(true) TH_LOG("OPEN_TREE_NAMESPACE succeeded without caps"); + break; + case 2: + SKIP(return, "setup_userns failed"); + break; + case 3: + SKIP(return, "caps_down failed"); + break; + case 4: + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + break; + default: + ASSERT_FALSE(true) TH_LOG("Unexpected error in child (exit %d)", + WEXITSTATUS(status)); + break; + } +} + +FIXTURE(open_tree_ns_userns) +{ + int fd; +}; + +FIXTURE_SETUP(open_tree_ns_userns) +{ + int ret; + + self->fd = -1; + + /* Check if open_tree syscall is supported */ + ret = sys_open_tree(-1, NULL, 0); + if (ret == -1 && errno == ENOSYS) + SKIP(return, "open_tree() syscall not supported"); + + /* Check if statmount/listmount are supported */ + ret = statmount(0, 0, 0, NULL, 0, 0); + if (ret == -1 && errno == ENOSYS) + SKIP(return, "statmount() syscall not supported"); +} + +FIXTURE_TEARDOWN(open_tree_ns_userns) +{ + if (self->fd >= 0) + close(self->fd); +} + +TEST_F(open_tree_ns_userns, create_in_userns) +{ + pid_t pid; + int status; + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int fd; + + /* Create new user namespace (also creates mount namespace) */ + if (enter_userns() != 0) + _exit(2); + + /* Now we have CAP_SYS_ADMIN in the user namespace */ + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC); + if (fd < 0) { + if (errno == EINVAL) + _exit(4); /* OPEN_TREE_NAMESPACE not supported */ + _exit(1); + } + + /* Verify we can get the namespace ID */ + if (get_mnt_ns_id(fd, &new_ns_id) != 0) + _exit(5); + + /* Verify we can list mounts in the new namespace */ + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, 0); + if (nr_mounts < 0) + _exit(6); + + /* Should have at least 1 mount */ + if (nr_mounts < 1) + _exit(7); + + close(fd); + _exit(0); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + + switch (WEXITSTATUS(status)) { + case 0: + /* Success */ + break; + case 1: + ASSERT_FALSE(true) TH_LOG("open_tree(OPEN_TREE_NAMESPACE) failed in userns"); + break; + case 2: + SKIP(return, "setup_userns failed"); + break; + case 4: + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + break; + case 5: + ASSERT_FALSE(true) TH_LOG("Failed to get mount namespace ID"); + break; + case 6: + ASSERT_FALSE(true) TH_LOG("listmount failed in new namespace"); + break; + case 7: + ASSERT_FALSE(true) TH_LOG("New namespace has no mounts"); + break; + default: + ASSERT_FALSE(true) TH_LOG("Unexpected error in child (exit %d)", + WEXITSTATUS(status)); + break; + } +} + +TEST_F(open_tree_ns_userns, setns_in_userns) +{ + pid_t pid; + int status; + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + uint64_t new_ns_id; + int fd; + pid_t inner_pid; + int inner_status; + + /* Create new user namespace */ + if (enter_userns() != 0) + _exit(2); + + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC); + if (fd < 0) { + if (errno == EINVAL) + _exit(4); + _exit(1); + } + + if (get_mnt_ns_id(fd, &new_ns_id) != 0) + _exit(5); + + /* Fork again to test setns into the new namespace */ + inner_pid = fork(); + if (inner_pid < 0) + _exit(8); + + if (inner_pid == 0) { + /* Inner child: enter the new namespace */ + if (setns(fd, CLONE_NEWNS) < 0) + _exit(1); + _exit(0); + } + + if (waitpid(inner_pid, &inner_status, 0) != inner_pid) + _exit(9); + + if (!WIFEXITED(inner_status) || WEXITSTATUS(inner_status) != 0) + _exit(10); + + close(fd); + _exit(0); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + + switch (WEXITSTATUS(status)) { + case 0: + /* Success */ + break; + case 1: + ASSERT_FALSE(true) TH_LOG("open_tree or setns failed in userns"); + break; + case 2: + SKIP(return, "setup_userns failed"); + break; + case 4: + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + break; + case 5: + ASSERT_FALSE(true) TH_LOG("Failed to get mount namespace ID"); + break; + case 8: + ASSERT_FALSE(true) TH_LOG("Inner fork failed"); + break; + case 9: + ASSERT_FALSE(true) TH_LOG("Inner waitpid failed"); + break; + case 10: + ASSERT_FALSE(true) TH_LOG("setns into new namespace failed"); + break; + default: + ASSERT_FALSE(true) TH_LOG("Unexpected error in child (exit %d)", + WEXITSTATUS(status)); + break; + } +} + +TEST_F(open_tree_ns_userns, recursive_in_userns) +{ + pid_t pid; + int status; + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int fd; + + /* Create new user namespace */ + if (enter_userns() != 0) + _exit(2); + + /* Test recursive flag in userns */ + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC); + if (fd < 0) { + if (errno == EINVAL) + _exit(4); + _exit(1); + } + + if (get_mnt_ns_id(fd, &new_ns_id) != 0) + _exit(5); + + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, 0); + if (nr_mounts < 0) + _exit(6); + + /* Recursive should copy submounts too */ + if (nr_mounts < 1) + _exit(7); + + close(fd); + _exit(0); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + + switch (WEXITSTATUS(status)) { + case 0: + /* Success */ + break; + case 1: + ASSERT_FALSE(true) TH_LOG("open_tree(OPEN_TREE_NAMESPACE|AT_RECURSIVE) failed in userns"); + break; + case 2: + SKIP(return, "setup_userns failed"); + break; + case 4: + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + break; + case 5: + ASSERT_FALSE(true) TH_LOG("Failed to get mount namespace ID"); + break; + case 6: + ASSERT_FALSE(true) TH_LOG("listmount failed in new namespace"); + break; + case 7: + ASSERT_FALSE(true) TH_LOG("New namespace has no mounts"); + break; + default: + ASSERT_FALSE(true) TH_LOG("Unexpected error in child (exit %d)", + WEXITSTATUS(status)); + break; + } +} + +TEST_F(open_tree_ns_userns, umount_fails_einval) +{ + pid_t pid; + int status; + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int fd; + ssize_t i; + + /* Create new user namespace */ + if (enter_userns() != 0) + _exit(2); + + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC); + if (fd < 0) { + if (errno == EINVAL) + _exit(4); + _exit(1); + } + + if (get_mnt_ns_id(fd, &new_ns_id) != 0) + _exit(5); + + /* Get all mounts in the new namespace */ + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, LISTMOUNT_REVERSE); + if (nr_mounts < 0) + _exit(9); + + if (nr_mounts < 1) + _exit(10); + + /* Enter the new namespace */ + if (setns(fd, CLONE_NEWNS) < 0) + _exit(6); + + for (i = 0; i < nr_mounts; i++) { + struct statmount *sm; + const char *mnt_point; + + sm = statmount_alloc(list[i], new_ns_id, + STATMOUNT_MNT_POINT); + if (!sm) + _exit(11); + + mnt_point = sm->str + sm->mnt_point; + + TH_LOG("Trying to umount %s", mnt_point); + if (umount2(mnt_point, MNT_DETACH) == 0) { + free(sm); + _exit(7); + } + + if (errno != EINVAL) { + /* Wrong error */ + free(sm); + _exit(8); + } + + free(sm); + } + + close(fd); + _exit(0); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + + switch (WEXITSTATUS(status)) { + case 0: + break; + case 1: + ASSERT_FALSE(true) TH_LOG("open_tree(OPEN_TREE_NAMESPACE) failed"); + break; + case 2: + SKIP(return, "setup_userns failed"); + break; + case 4: + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + break; + case 5: + ASSERT_FALSE(true) TH_LOG("Failed to get mount namespace ID"); + break; + case 6: + ASSERT_FALSE(true) TH_LOG("setns into new namespace failed"); + break; + case 7: + ASSERT_FALSE(true) TH_LOG("umount succeeded but should have failed with EINVAL"); + break; + case 8: + ASSERT_FALSE(true) TH_LOG("umount failed with wrong error (expected EINVAL)"); + break; + case 9: + ASSERT_FALSE(true) TH_LOG("listmount failed"); + break; + case 10: + ASSERT_FALSE(true) TH_LOG("No mounts in new namespace"); + break; + case 11: + ASSERT_FALSE(true) TH_LOG("statmount_alloc failed"); + break; + default: + ASSERT_FALSE(true) TH_LOG("Unexpected error in child (exit %d)", + WEXITSTATUS(status)); + break; + } +} + +TEST_F(open_tree_ns_userns, umount_succeeds) +{ + pid_t pid; + int status; + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int fd; + ssize_t i; + + if (unshare(CLONE_NEWNS)) + _exit(1); + + if (sys_mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) != 0) + _exit(1); + + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC); + if (fd < 0) { + if (errno == EINVAL) + _exit(4); + _exit(1); + } + + if (get_mnt_ns_id(fd, &new_ns_id) != 0) + _exit(5); + + /* Get all mounts in the new namespace */ + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, LISTMOUNT_REVERSE); + if (nr_mounts < 0) + _exit(9); + + if (nr_mounts < 1) + _exit(10); + + /* Enter the new namespace */ + if (setns(fd, CLONE_NEWNS) < 0) + _exit(6); + + for (i = 0; i < nr_mounts; i++) { + struct statmount *sm; + const char *mnt_point; + + sm = statmount_alloc(list[i], new_ns_id, + STATMOUNT_MNT_POINT); + if (!sm) + _exit(11); + + mnt_point = sm->str + sm->mnt_point; + + TH_LOG("Trying to umount %s", mnt_point); + if (umount2(mnt_point, MNT_DETACH) != 0) { + free(sm); + _exit(7); + } + + free(sm); + } + + close(fd); + _exit(0); + } + + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + + switch (WEXITSTATUS(status)) { + case 0: + break; + case 1: + ASSERT_FALSE(true) TH_LOG("open_tree(OPEN_TREE_NAMESPACE) failed"); + break; + case 2: + SKIP(return, "setup_userns failed"); + break; + case 4: + SKIP(return, "OPEN_TREE_NAMESPACE not supported"); + break; + case 5: + ASSERT_FALSE(true) TH_LOG("Failed to get mount namespace ID"); + break; + case 6: + ASSERT_FALSE(true) TH_LOG("setns into new namespace failed"); + break; + case 7: + ASSERT_FALSE(true) TH_LOG("umount succeeded but should have failed with EINVAL"); + break; + case 9: + ASSERT_FALSE(true) TH_LOG("listmount failed"); + break; + case 10: + ASSERT_FALSE(true) TH_LOG("No mounts in new namespace"); + break; + case 11: + ASSERT_FALSE(true) TH_LOG("statmount_alloc failed"); + break; + default: + ASSERT_FALSE(true) TH_LOG("Unexpected error in child (exit %d)", + WEXITSTATUS(status)); + break; + } +} + +FIXTURE(open_tree_ns_unbindable) +{ + char tmpdir[PATH_MAX]; + bool mounted; +}; + +FIXTURE_SETUP(open_tree_ns_unbindable) +{ + int ret; + + self->mounted = false; + + /* Check if open_tree syscall is supported */ + ret = sys_open_tree(-1, NULL, 0); + if (ret == -1 && errno == ENOSYS) + SKIP(return, "open_tree() syscall not supported"); + + /* Create a temporary directory for the test mount */ + snprintf(self->tmpdir, sizeof(self->tmpdir), + "/tmp/open_tree_ns_test.XXXXXX"); + ASSERT_NE(mkdtemp(self->tmpdir), NULL); + + /* Mount tmpfs there */ + ret = mount("tmpfs", self->tmpdir, "tmpfs", 0, NULL); + if (ret < 0) { + rmdir(self->tmpdir); + SKIP(return, "Failed to mount tmpfs"); + } + self->mounted = true; + + ret = mount(NULL, self->tmpdir, NULL, MS_UNBINDABLE, NULL); + if (ret < 0) { + rmdir(self->tmpdir); + SKIP(return, "Failed to make tmpfs unbindable"); + } +} + +FIXTURE_TEARDOWN(open_tree_ns_unbindable) +{ + if (self->mounted) + umount2(self->tmpdir, MNT_DETACH); + rmdir(self->tmpdir); +} + +TEST_F(open_tree_ns_unbindable, fails_on_unbindable) +{ + int fd; + + fd = sys_open_tree(AT_FDCWD, self->tmpdir, + OPEN_TREE_NAMESPACE | OPEN_TREE_CLOEXEC); + ASSERT_LT(fd, 0); +} + +TEST_F(open_tree_ns_unbindable, recursive_skips_on_unbindable) +{ + uint64_t new_ns_id; + uint64_t list[256]; + ssize_t nr_mounts; + int fd; + ssize_t i; + bool found_unbindable = false; + + fd = sys_open_tree(AT_FDCWD, "/", + OPEN_TREE_NAMESPACE | AT_RECURSIVE | OPEN_TREE_CLOEXEC); + ASSERT_GT(fd, 0); + + ASSERT_EQ(get_mnt_ns_id(fd, &new_ns_id), 0); + + nr_mounts = listmount(LSMT_ROOT, new_ns_id, 0, list, 256, 0); + ASSERT_GE(nr_mounts, 0) { + TH_LOG("listmount failed: %m"); + } + + /* + * Iterate through all mounts in the new namespace and verify + * the unbindable tmpfs mount was silently dropped. + */ + for (i = 0; i < nr_mounts; i++) { + struct statmount *sm; + const char *mnt_point; + + sm = statmount_alloc(list[i], new_ns_id, STATMOUNT_MNT_POINT); + ASSERT_NE(sm, NULL) { + TH_LOG("statmount_alloc failed for mnt_id %llu", + (unsigned long long)list[i]); + } + + mnt_point = sm->str + sm->mnt_point; + + if (strcmp(mnt_point, self->tmpdir) == 0) { + TH_LOG("Found unbindable mount at %s (should have been dropped)", + mnt_point); + found_unbindable = true; + } + + free(sm); + } + + ASSERT_FALSE(found_unbindable) { + TH_LOG("Unbindable mount at %s was not dropped", self->tmpdir); + } + + close(fd); +} + +TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/filesystems/utils.c b/tools/testing/selftests/filesystems/utils.c index c9dd5412b37b..d6f26f849053 100644 --- a/tools/testing/selftests/filesystems/utils.c +++ b/tools/testing/selftests/filesystems/utils.c @@ -515,6 +515,32 @@ int setup_userns(void) return 0; } +int enter_userns(void) +{ + int ret; + char buf[32]; + uid_t uid = getuid(); + gid_t gid = getgid(); + + ret = unshare(CLONE_NEWUSER); + if (ret) + return ret; + + sprintf(buf, "0 %d 1", uid); + ret = write_file("/proc/self/uid_map", buf); + if (ret) + return ret; + ret = write_file("/proc/self/setgroups", "deny"); + if (ret) + return ret; + sprintf(buf, "0 %d 1", gid); + ret = write_file("/proc/self/gid_map", buf); + if (ret) + return ret; + + return 0; +} + /* caps_down - lower all effective caps */ int caps_down(void) { diff --git a/tools/testing/selftests/filesystems/utils.h b/tools/testing/selftests/filesystems/utils.h index 70f7ccc607f4..0bccfed666a9 100644 --- a/tools/testing/selftests/filesystems/utils.h +++ b/tools/testing/selftests/filesystems/utils.h @@ -28,6 +28,7 @@ extern int cap_down(cap_value_t down); extern bool switch_ids(uid_t uid, gid_t gid); extern int setup_userns(void); +extern int enter_userns(void); static inline bool switch_userns(int fd, uid_t uid, gid_t gid, bool drop_caps) {