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authorLinus Torvalds <torvalds@linux-foundation.org>2020-08-04 14:40:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-04 14:40:07 -0700
commit0a72761b27fe3b10e3f336bf2f2aa22635504cdd (patch)
treefbd99b0eac76464388070ef29153b9c8d596dc5f
parent3950e975431bc914f7e81b8f2a2dbdf2064acb0f (diff)
parent55d9ad97e417cc2604654913e902d26f942bde00 (diff)
downloadlwn-0a72761b27fe3b10e3f336bf2f2aa22635504cdd.tar.gz
lwn-0a72761b27fe3b10e3f336bf2f2aa22635504cdd.zip
Merge tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull thread updates from Christian Brauner: "This contains the changes to add the missing support for attaching to time namespaces via pidfds. Last cycle setns() was changed to support attaching to multiple namespaces atomically. This requires all namespaces to have a point of no return where they can't fail anymore. Specifically, <namespace-type>_install() is allowed to perform permission checks and install the namespace into the new struct nsset that it has been given but it is not allowed to make visible changes to the affected task. Once <namespace-type>_install() returns, anything that the given namespace type additionally requires to be setup needs to ideally be done in a function that can't fail or if it fails the failure must be non-fatal. For time namespaces the relevant functions that fell into this category were timens_set_vvar_page() and vdso_join_timens(). The latter could still fail although it didn't need to. This function is only implemented for vdso_join_timens() in current mainline. As discussed on-list (cf. [1]), in order to make setns() support time namespaces when attaching to multiple namespaces at once properly we changed vdso_join_timens() to always succeed. So vdso_join_timens() replaces the mmap_write_lock_killable() with mmap_read_lock(). Please note that arm is about to grow vdso support for time namespaces (possibly this merge window). We've synced on this change and arm64 also uses mmap_read_lock(), i.e. makes vdso_join_timens() a function that can't fail. Once the changes here and the arm64 changes have landed, vdso_join_timens() should be turned into a void function so it's obvious to callers and implementers on other architectures that the expectation is that it can't fail. We didn't do this right away because it would've introduced unnecessary merge conflicts between the two trees for no major gain. As always, tests included" [1]: https://lore.kernel.org/lkml/20200611110221.pgd3r5qkjrjmfqa2@wittgenstein * tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: tests: add CLONE_NEWTIME setns tests nsproxy: support CLONE_NEWTIME with setns() timens: add timens_commit() helper timens: make vdso_join_timens() always succeed
-rw-r--r--arch/x86/entry/vdso/vma.c5
-rw-r--r--include/linux/time_namespace.h6
-rw-r--r--kernel/nsproxy.c21
-rw-r--r--kernel/time/namespace.c22
-rw-r--r--tools/testing/selftests/pidfd/pidfd.h4
-rw-r--r--tools/testing/selftests/pidfd/pidfd_setns_test.c76
6 files changed, 115 insertions, 19 deletions
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index ea7c1f0b79df..9185cb1d13b9 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -144,8 +144,7 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
struct mm_struct *mm = task->mm;
struct vm_area_struct *vma;
- if (mmap_write_lock_killable(mm))
- return -EINTR;
+ mmap_read_lock(mm);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
unsigned long size = vma->vm_end - vma->vm_start;
@@ -154,7 +153,7 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
zap_page_range(vma, vma->vm_start, size);
}
- mmap_write_unlock(mm);
+ mmap_read_unlock(mm);
return 0;
}
#else
diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index 824d54e057eb..5b6031385db0 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -33,6 +33,7 @@ extern struct time_namespace init_time_ns;
#ifdef CONFIG_TIME_NS
extern int vdso_join_timens(struct task_struct *task,
struct time_namespace *ns);
+extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);
static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
{
@@ -96,6 +97,11 @@ static inline int vdso_join_timens(struct task_struct *task,
return 0;
}
+static inline void timens_commit(struct task_struct *tsk,
+ struct time_namespace *ns)
+{
+}
+
static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
{
return NULL;
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index cd356630a311..12dd41b39a7f 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -262,8 +262,8 @@ void exit_task_namespaces(struct task_struct *p)
static int check_setns_flags(unsigned long flags)
{
if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
- CLONE_NEWNET | CLONE_NEWUSER | CLONE_NEWPID |
- CLONE_NEWCGROUP)))
+ CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER |
+ CLONE_NEWPID | CLONE_NEWCGROUP)))
return -EINVAL;
#ifndef CONFIG_USER_NS
@@ -290,6 +290,10 @@ static int check_setns_flags(unsigned long flags)
if (flags & CLONE_NEWNET)
return -EINVAL;
#endif
+#ifndef CONFIG_TIME_NS
+ if (flags & CLONE_NEWTIME)
+ return -EINVAL;
+#endif
return 0;
}
@@ -464,6 +468,14 @@ static int validate_nsset(struct nsset *nsset, struct pid *pid)
}
#endif
+#ifdef CONFIG_TIME_NS
+ if (flags & CLONE_NEWTIME) {
+ ret = validate_ns(nsset, &nsp->time_ns->ns);
+ if (ret)
+ goto out;
+ }
+#endif
+
out:
if (pid_ns)
put_pid_ns(pid_ns);
@@ -507,6 +519,11 @@ static void commit_nsset(struct nsset *nsset)
exit_sem(me);
#endif
+#ifdef CONFIG_TIME_NS
+ if (flags & CLONE_NEWTIME)
+ timens_commit(me, nsset->nsproxy->time_ns);
+#endif
+
/* transfer ownership */
switch_task_namespaces(me, nsset->nsproxy);
nsset->nsproxy = NULL;
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index 5d9fc22d836a..afc65e6be33e 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -280,11 +280,16 @@ static void timens_put(struct ns_common *ns)
put_time_ns(to_time_ns(ns));
}
+void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
+{
+ timens_set_vvar_page(tsk, ns);
+ vdso_join_timens(tsk, ns);
+}
+
static int timens_install(struct nsset *nsset, struct ns_common *new)
{
struct nsproxy *nsproxy = nsset->nsproxy;
struct time_namespace *ns = to_time_ns(new);
- int err;
if (!current_is_single_threaded())
return -EUSERS;
@@ -293,12 +298,6 @@ static int timens_install(struct nsset *nsset, struct ns_common *new)
!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
return -EPERM;
- timens_set_vvar_page(current, ns);
-
- err = vdso_join_timens(current, ns);
- if (err)
- return err;
-
get_time_ns(ns);
put_time_ns(nsproxy->time_ns);
nsproxy->time_ns = ns;
@@ -313,22 +312,17 @@ int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
{
struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
struct time_namespace *ns = to_time_ns(nsc);
- int err;
/* create_new_namespaces() already incremented the ref counter */
if (nsproxy->time_ns == nsproxy->time_ns_for_children)
return 0;
- timens_set_vvar_page(tsk, ns);
-
- err = vdso_join_timens(tsk, ns);
- if (err)
- return err;
-
get_time_ns(ns);
put_time_ns(nsproxy->time_ns);
nsproxy->time_ns = ns;
+ timens_commit(tsk, ns);
+
return 0;
}
diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
index 8d728eda783d..a2c80914e3dc 100644
--- a/tools/testing/selftests/pidfd/pidfd.h
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -22,6 +22,10 @@
#define P_PIDFD 3
#endif
+#ifndef CLONE_NEWTIME
+#define CLONE_NEWTIME 0x00000080
+#endif
+
#ifndef CLONE_PIDFD
#define CLONE_PIDFD 0x00001000
#endif
diff --git a/tools/testing/selftests/pidfd/pidfd_setns_test.c b/tools/testing/selftests/pidfd/pidfd_setns_test.c
index 9418108eae13..7a27dbe07e23 100644
--- a/tools/testing/selftests/pidfd/pidfd_setns_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_setns_test.c
@@ -32,6 +32,7 @@ enum {
PIDFD_NS_NET,
PIDFD_NS_CGROUP,
PIDFD_NS_PIDCLD,
+ PIDFD_NS_TIME,
PIDFD_NS_MAX
};
@@ -47,6 +48,7 @@ const struct ns_info {
[PIDFD_NS_NET] = { "net", CLONE_NEWNET, },
[PIDFD_NS_CGROUP] = { "cgroup", CLONE_NEWCGROUP, },
[PIDFD_NS_PIDCLD] = { "pid_for_children", 0, },
+ [PIDFD_NS_TIME] = { "time", CLONE_NEWTIME, },
};
FIXTURE(current_nsset)
@@ -83,9 +85,49 @@ pid_t create_child(int *pidfd, unsigned flags)
return sys_clone3(&args, sizeof(struct clone_args));
}
+static bool switch_timens(void)
+{
+ int fd, ret;
+
+ if (unshare(CLONE_NEWTIME))
+ return false;
+
+ fd = open("/proc/self/ns/time_for_children", O_RDONLY | O_CLOEXEC);
+ if (fd < 0)
+ return false;
+
+ ret = setns(fd, CLONE_NEWTIME);
+ close(fd);
+ return ret == 0;
+}
+
+static ssize_t read_nointr(int fd, void *buf, size_t count)
+{
+ ssize_t ret;
+
+ do {
+ ret = read(fd, buf, count);
+ } while (ret < 0 && errno == EINTR);
+
+ return ret;
+}
+
+static ssize_t write_nointr(int fd, const void *buf, size_t count)
+{
+ ssize_t ret;
+
+ do {
+ ret = write(fd, buf, count);
+ } while (ret < 0 && errno == EINTR);
+
+ return ret;
+}
+
FIXTURE_SETUP(current_nsset)
{
int i, proc_fd, ret;
+ int ipc_sockets[2];
+ char c;
for (i = 0; i < PIDFD_NS_MAX; i++) {
self->nsfds[i] = -EBADF;
@@ -130,6 +172,9 @@ FIXTURE_SETUP(current_nsset)
TH_LOG("%m - Failed to open pidfd for process %d", self->pid);
}
+ ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
+ EXPECT_EQ(ret, 0);
+
/* Create tasks that will be stopped. */
self->child_pid1 = create_child(&self->child_pidfd1,
CLONE_NEWUSER | CLONE_NEWNS |
@@ -139,10 +184,27 @@ FIXTURE_SETUP(current_nsset)
EXPECT_GE(self->child_pid1, 0);
if (self->child_pid1 == 0) {
+ close(ipc_sockets[0]);
+
+ if (!switch_timens())
+ _exit(EXIT_FAILURE);
+
+ if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+ _exit(EXIT_FAILURE);
+
+ close(ipc_sockets[1]);
+
pause();
_exit(EXIT_SUCCESS);
}
+ close(ipc_sockets[1]);
+ ASSERT_EQ(read_nointr(ipc_sockets[0], &c, 1), 1);
+ close(ipc_sockets[0]);
+
+ ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
+ EXPECT_EQ(ret, 0);
+
self->child_pid2 = create_child(&self->child_pidfd2,
CLONE_NEWUSER | CLONE_NEWNS |
CLONE_NEWCGROUP | CLONE_NEWIPC |
@@ -151,10 +213,24 @@ FIXTURE_SETUP(current_nsset)
EXPECT_GE(self->child_pid2, 0);
if (self->child_pid2 == 0) {
+ close(ipc_sockets[0]);
+
+ if (!switch_timens())
+ _exit(EXIT_FAILURE);
+
+ if (write_nointr(ipc_sockets[1], "1", 1) < 0)
+ _exit(EXIT_FAILURE);
+
+ close(ipc_sockets[1]);
+
pause();
_exit(EXIT_SUCCESS);
}
+ close(ipc_sockets[1]);
+ ASSERT_EQ(read_nointr(ipc_sockets[0], &c, 1), 1);
+ close(ipc_sockets[0]);
+
for (i = 0; i < PIDFD_NS_MAX; i++) {
char p[100];