The main motivation to add set_tid to clone3() is CRIU.
To restore a process with the same PID/TID CRIU currently uses
/proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to
ns_last_pid and then (quickly) does a clone(). This works most of the
time, but it is racy. It is also slow as it requires multiple syscalls.
Extending clone3() to support *set_tid makes it possible restore a
process using CRIU without accessing /proc/sys/kernel/ns_last_pid and
race free (as long as the desired PID/TID is available).
This clone3() extension places the same restrictions (CAP_SYS_ADMIN)
on clone3() with *set_tid as they are currently in place for ns_last_pid.
The original version of this change was using a single value for
set_tid. At the 2019 LPC, after presenting set_tid, it was, however,
decided to change set_tid to an array to enable setting the PID of a
process in multiple PID namespaces at the same time. If a process is
created in a PID namespace it is possible to influence the PID inside
and outside of the PID namespace. Details also in the corresponding
selftest.
To create a process with the following PIDs:
PID NS level Requested PID
0 (host) 31496
1 42
2 1
For that example the two newly introduced parameters to struct
clone_args (set_tid and set_tid_size) would need to be:
set_tid[0] = 1;
set_tid[1] = 42;
set_tid[2] = 31496;
set_tid_size = 3;
If only the PIDs of the two innermost nested PID namespaces should be
defined it would look like this:
set_tid[0] = 1;
set_tid[1] = 42;
set_tid_size = 2;
The PID of the newly created process would then be the next available
free PID in the PID namespace level 0 (host) and 42 in the PID namespace
at level 1 and the PID of the process in the innermost PID namespace
would be 1.
The set_tid array is used to specify the PID of a process starting
from the innermost nested PID namespaces up to set_tid_size PID namespaces.
set_tid_size cannot be larger then the current PID namespace level.
Signed-off-by: Adrian Reber <[email protected]>
---
v2:
- Removed (size < sizeof(struct clone_args)) as discussed with
Christian and Dmitry
- Added comment to ((set_tid != 1) && idr_get_cursor() <= 1) (Oleg)
- Use idr_alloc() instead of idr_alloc_cyclic() (Oleg)
v3:
- Return EEXIST if PID is already in use (Christian)
- Drop CLONE_SET_TID (Christian and Oleg)
- Use idr_is_empty() instead of idr_get_cursor() (Oleg)
- Handle different `struct clone_args` sizes (Dmitry)
v4:
- Rework struct size check with defines (Christian)
- Reduce number of set_tid checks (Oleg)
- Less parentheses and more robust code (Oleg)
- Do ns_capable() on correct user_ns (Oleg, Christian)
v5:
- make set_tid checks earlier in alloc_pid() (Christian)
- remove unnecessary comment and struct size check (Christian)
v6:
- remove CLONE_SET_TID from description (Christian)
- add clone3() tests for different clone_args sizes (Christian)
- move more set_tid checks to alloc_pid() (Oleg)
- make all set_tid checks lockless (Oleg)
v7:
- changed set_tid to be an array to set the PID of a process
in multiple nested PID namespaces at the same time as discussed
at LPC 2019 (container MC)
v8:
- skip unnecessary memset() (Rasmus)
- replace set_tid copy loop with a single copy (Christian)
- more parameter error checking (Christian)
- cache set_tid in alloc_pid() (Oleg)
- move code in "else" branch (Oleg)
---
include/linux/pid.h | 3 +-
include/linux/pid_namespace.h | 2 ++
include/linux/sched/task.h | 3 ++
include/uapi/linux/sched.h | 2 ++
kernel/fork.c | 24 ++++++++++++-
kernel/pid.c | 64 +++++++++++++++++++++++++++--------
kernel/pid_namespace.c | 2 --
7 files changed, 82 insertions(+), 18 deletions(-)
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 9645b1194c98..034b7df25888 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -120,7 +120,8 @@ extern struct pid *find_vpid(int nr);
extern struct pid *find_get_pid(int nr);
extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
-extern struct pid *alloc_pid(struct pid_namespace *ns);
+extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
+ size_t set_tid_size);
extern void free_pid(struct pid *pid);
extern void disable_pid_allocation(struct pid_namespace *ns);
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 49538b172483..2ed6af88794b 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -12,6 +12,8 @@
#include <linux/ns_common.h>
#include <linux/idr.h>
+/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
+#define MAX_PID_NS_LEVEL 32
struct fs_pin;
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 4b1c3b664f51..f1879884238e 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -26,6 +26,9 @@ struct kernel_clone_args {
unsigned long stack;
unsigned long stack_size;
unsigned long tls;
+ pid_t *set_tid;
+ /* Number of elements in *set_tid */
+ size_t set_tid_size;
};
/*
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 25b4fa00bad1..13f74c40a629 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -72,6 +72,8 @@ struct clone_args {
__aligned_u64 stack;
__aligned_u64 stack_size;
__aligned_u64 tls;
+ __aligned_u64 set_tid;
+ __aligned_u64 set_tid_size;
};
#endif
diff --git a/kernel/fork.c b/kernel/fork.c
index 55af6931c6ec..6f9e6443e12c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2026,7 +2026,8 @@ static __latent_entropy struct task_struct *copy_process(
stackleak_task_init(p);
if (pid != &init_struct_pid) {
- pid = alloc_pid(p->nsproxy->pid_ns_for_children);
+ pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
+ args->set_tid_size);
if (IS_ERR(pid)) {
retval = PTR_ERR(pid);
goto bad_fork_cleanup_thread;
@@ -2529,6 +2530,7 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
{
int err;
struct clone_args args;
+ pid_t *kset_tid = kargs->set_tid;
if (unlikely(usize > PAGE_SIZE))
return -E2BIG;
@@ -2539,6 +2541,15 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
if (err)
return err;
+ if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
+ return -EINVAL;
+
+ if (unlikely(!args.set_tid && args.set_tid_size > 0))
+ return -EINVAL;
+
+ if (unlikely(args.set_tid && args.set_tid_size == 0))
+ return -EINVAL;
+
/*
* Verify that higher 32bits of exit_signal are unset and that
* it is a valid signal
@@ -2556,8 +2567,16 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
.stack = args.stack,
.stack_size = args.stack_size,
.tls = args.tls,
+ .set_tid_size = args.set_tid_size,
};
+ if (args.set_tid &&
+ copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
+ (kargs->set_tid_size * sizeof(pid_t))))
+ return -EFAULT;
+
+ kargs->set_tid = kset_tid;
+
return 0;
}
@@ -2631,6 +2650,9 @@ SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
int err;
struct kernel_clone_args kargs;
+ pid_t set_tid[MAX_PID_NS_LEVEL];
+
+ kargs.set_tid = set_tid;
err = copy_clone_args_from_user(&kargs, uargs, size);
if (err)
diff --git a/kernel/pid.c b/kernel/pid.c
index 0a9f2e437217..17280da48224 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -157,7 +157,8 @@ void free_pid(struct pid *pid)
call_rcu(&pid->rcu, delayed_put_pid);
}
-struct pid *alloc_pid(struct pid_namespace *ns)
+struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
+ size_t set_tid_size)
{
struct pid *pid;
enum pid_type type;
@@ -166,6 +167,17 @@ struct pid *alloc_pid(struct pid_namespace *ns)
struct upid *upid;
int retval = -ENOMEM;
+ /*
+ * set_tid_size contains the size of the set_tid array. Starting at
+ * the most nested currently active PID namespace it tells alloc_pid()
+ * which PID to set for a process in that most nested PID namespace
+ * up to set_tid_size PID namespaces. It does not have to set the PID
+ * for a process in all nested PID namespaces but set_tid_size must
+ * never be greater than the current ns->level + 1.
+ */
+ if (set_tid_size > ns->level + 1)
+ return ERR_PTR(-EINVAL);
+
pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
if (!pid)
return ERR_PTR(retval);
@@ -175,23 +187,47 @@ struct pid *alloc_pid(struct pid_namespace *ns)
for (i = ns->level; i >= 0; i--) {
int pid_min = 1;
+ int tid = 0;
+
+ if (set_tid_size) {
+ tid = set_tid[ns->level - i];
+ if (tid < 1 || tid >= pid_max)
+ return ERR_PTR(-EINVAL);
+ /* Also fail if a PID != 1 is requested and no PID 1 exists */
+ if (tid != 1 && !tmp->child_reaper)
+ return ERR_PTR(-EINVAL);
+ if (!ns_capable(tmp->user_ns, CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+ }
idr_preload(GFP_KERNEL);
spin_lock_irq(&pidmap_lock);
- /*
- * init really needs pid 1, but after reaching the maximum
- * wrap back to RESERVED_PIDS
- */
- if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
- pid_min = RESERVED_PIDS;
-
- /*
- * Store a null pointer so find_pid_ns does not find
- * a partially initialized PID (see below).
- */
- nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
- pid_max, GFP_ATOMIC);
+ if (tid) {
+ nr = idr_alloc(&tmp->idr, NULL, tid,
+ tid + 1, GFP_ATOMIC);
+ /*
+ * If ENOSPC is returned it means that the PID is
+ * alreay in use. Return EEXIST in that case.
+ */
+ if (nr == -ENOSPC)
+ nr = -EEXIST;
+ set_tid_size--;
+ } else {
+ /*
+ * init really needs pid 1, but after reaching the maximum
+ * wrap back to RESERVED_PIDS
+ */
+ if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
+ pid_min = RESERVED_PIDS;
+
+ /*
+ * Store a null pointer so find_pid_ns does not find
+ * a partially initialized PID (see below).
+ */
+ nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
+ pid_max, GFP_ATOMIC);
+ }
spin_unlock_irq(&pidmap_lock);
idr_preload_end();
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a6a79f85c81a..d40017e79ebe 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -26,8 +26,6 @@
static DEFINE_MUTEX(pid_caches_mutex);
static struct kmem_cache *pid_ns_cachep;
-/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
-#define MAX_PID_NS_LEVEL 32
/* Write once array, filled from the beginning. */
static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];
--
2.23.0
This tests clone3() with *set_tid to see if all desired PIDs are working
as expected. The tests are trying multiple invalid input parameters as
well as creating processes while specifying a certain PID in multiple
PID namespaces at the same time.
Signed-off-by: Adrian Reber <[email protected]>
---
tools/testing/selftests/clone3/.gitignore | 1 +
tools/testing/selftests/clone3/Makefile | 2 +-
.../testing/selftests/clone3/clone3_set_tid.c | 345 ++++++++++++++++++
3 files changed, 347 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/clone3/clone3_set_tid.c
diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore
index 85d9d3ba2524..d56c3c49d869 100644
--- a/tools/testing/selftests/clone3/.gitignore
+++ b/tools/testing/selftests/clone3/.gitignore
@@ -1 +1,2 @@
clone3
+clone3_set_tid
diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
index ea922c014ae4..2d292545ca8e 100644
--- a/tools/testing/selftests/clone3/Makefile
+++ b/tools/testing/selftests/clone3/Makefile
@@ -2,6 +2,6 @@
CFLAGS += -I../../../../usr/include/
-TEST_GEN_PROGS := clone3
+TEST_GEN_PROGS := clone3 clone3_set_tid
include ../lib.mk
diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c b/tools/testing/selftests/clone3/clone3_set_tid.c
new file mode 100644
index 000000000000..9a234fd2031e
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_set_tid.c
@@ -0,0 +1,345 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Based on Christian Brauner's clone3() example.
+ * These tests are assuming to be running in the host's
+ * PID namespace.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sched.h>
+
+#include "../kselftest.h"
+
+#ifndef MAX_PID_NS_LEVEL
+#define MAX_PID_NS_LEVEL 32
+#endif
+
+static int pipe_1[2];
+static int pipe_2[2];
+
+static pid_t raw_clone(struct clone_args *args)
+{
+ return syscall(__NR_clone3, args, sizeof(struct clone_args));
+}
+
+static int call_clone3_set_tid(pid_t *set_tid,
+ size_t set_tid_size,
+ int flags,
+ int expected_pid,
+ int wait_for_it)
+{
+ int status;
+ int ret = 0;
+ pid_t pid = -1;
+ struct clone_args args = {0};
+
+ args.flags = flags;
+ args.exit_signal = SIGCHLD;
+ args.set_tid = (__u64)set_tid;
+ args.set_tid_size = set_tid_size;
+
+ pid = raw_clone(&args);
+ if (pid < 0) {
+ ksft_print_msg("%s - Failed to create new process\n",
+ strerror(errno));
+ return -errno;
+ }
+
+ if (pid == 0) {
+ char tmp = 0;
+ ksft_print_msg("I am the child, my PID is %d (expected %d)\n",
+ getpid(), set_tid[0]);
+ if (wait_for_it) {
+ ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
+ /* Signal the parent that the child is ready */
+ close(pipe_1[0]);
+ write(pipe_1[1], &tmp, 1);
+ close(pipe_1[1]);
+ close(pipe_2[1]);
+ read(pipe_2[0], &tmp, 1);
+ close(pipe_2[0]);
+ }
+
+ if (set_tid[0] != getpid())
+ _exit(EXIT_FAILURE);
+ _exit(EXIT_SUCCESS);
+ }
+
+ if (expected_pid == 0 || expected_pid == pid)
+ ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
+ getpid(), pid);
+ else {
+ ksft_print_msg(
+ "Expected child pid %d does not match actual pid %d\n",
+ expected_pid, pid);
+ ret = -1;
+ }
+
+ if (wait(&status) < 0) {
+ ksft_print_msg("Child returned %s\n", strerror(errno));
+ return -errno;
+ }
+ if (WEXITSTATUS(status))
+ return WEXITSTATUS(status);
+
+ return ret;
+}
+
+static void test_clone3_set_tid(pid_t *set_tid,
+ size_t set_tid_size,
+ int flags,
+ int expected,
+ int expected_pid,
+ int wait_for_it)
+{
+ int ret;
+
+ ksft_print_msg(
+ "[%d] Trying clone3() with CLONE_SET_TID to %d and 0x%x\n",
+ getpid(), set_tid[0], flags);
+ ret = call_clone3_set_tid(set_tid, set_tid_size, flags, expected_pid,
+ wait_for_it);
+ ksft_print_msg(
+ "[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n",
+ getpid(), set_tid[0], ret, expected);
+ if (ret != expected)
+ ksft_test_result_fail(
+ "[%d] Result (%d) is different than expected (%d)\n",
+ getpid(), ret, expected);
+ else
+ ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n",
+ getpid(), ret, expected);
+}
+int main(int argc, char *argv[])
+{
+ FILE *f;
+ char buf;
+ pid_t pid;
+ pid_t ns1;
+ pid_t ns2;
+ pid_t ns3;
+ int status;
+ char *proc;
+ int ret = -1;
+ pid_t ns_pid;
+ int pid_max = 0;
+ uid_t uid = getuid();
+ char line[1024] = {0};
+ pid_t set_tid[MAX_PID_NS_LEVEL * 2];
+ pid_t set_tid_small[1];
+
+ if (pipe(pipe_1) == -1 || pipe(pipe_2))
+ ksft_exit_fail_msg("pipe() failed\n");
+
+ ksft_print_header();
+ ksft_set_plan(27);
+
+ f = fopen("/proc/sys/kernel/pid_max", "r");
+ if (f == NULL)
+ ksft_exit_fail_msg(
+ "%s - Could not open /proc/sys/kernel/pid_max\n",
+ strerror(errno));
+ fscanf(f, "%d", &pid_max);
+ fclose(f);
+ ksft_print_msg("/proc/sys/kernel/pid_max %d\n", pid_max);
+
+ /* Try invalid settings */
+ memset(&set_tid, 0, sizeof(set_tid));
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -E2BIG, 0, 0);
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -E2BIG, 0, 0);
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0, -E2BIG, 0, 0);
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -E2BIG, 0, 0);
+
+ /* small set_tid array, but maximum set_tid_size */
+ /* Find the current active PID */
+ pid = fork();
+ if (pid == 0) {
+ ksft_print_msg("Child has PID %d\n", getpid());
+ _exit(EXIT_SUCCESS);
+ }
+ (void)wait(NULL);
+ /* After the child has finished, its PID should be free. */
+ set_tid_small[0] = pid;
+ /*
+ * There is a chance that this can return -EFAULT as the actual
+ * set_tid array has only one entry, but we are telling the kernel
+ * that it has the size MAX_PID_NS_LEVEL. This could lead to a
+ * situation where copy_from_user() fails. So far it always
+ * succeeds and copies random data (whatever is after set_tid_small).
+ */
+ test_clone3_set_tid(set_tid_small, MAX_PID_NS_LEVEL, 0, -EINVAL, 0, 0);
+
+ /*
+ * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
+ * nested PID namespace.
+ */
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
+
+ memset(&set_tid, 0xff, sizeof(set_tid));
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -E2BIG, 0, 0);
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -E2BIG, 0, 0);
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0, -E2BIG, 0, 0);
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -E2BIG, 0, 0);
+ /*
+ * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
+ * nested PID namespace.
+ */
+ test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
+
+ memset(&set_tid, 0, sizeof(set_tid));
+ /* Try with an invalid PID */
+ set_tid[0] = 0;
+ test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+ set_tid[0] = -1;
+ test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+ /* Claim that the set_tid array actually contains 2 elements. */
+ test_clone3_set_tid(set_tid, 2, 0, -EINVAL, 0, 0);
+ /* Try it in a new PID namespace */
+ if (uid == 0)
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+ else
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
+
+ /*
+ * Try with a valid PID (1) but as non-root. This should fail
+ * with -EPERM if running in the initial user namespace.
+ * As root it should tell us -EEXIST.
+ */
+ set_tid[0] = 1;
+ if (uid == 0)
+ test_clone3_set_tid(set_tid, 1, 0, -EEXIST, 0, 0);
+ else
+ test_clone3_set_tid(set_tid, 1, 0, -EPERM, 0, 0);
+
+ /* Try it in a new PID namespace */
+ if (uid == 0)
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, 0, 0, 0);
+ else
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
+
+ /* pid_max should fail everywhere */
+ set_tid[0] = pid_max;
+ test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+ if (uid == 0)
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+ else
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
+
+ if (uid != 0) {
+ /*
+ * All remaining tests require root. Tell the framework
+ * that all those tests are skipped as non-root.
+ */
+ ksft_cnt.ksft_xskip += ksft_plan - ksft_test_num();
+ goto out;
+ }
+
+ /* Find the current active PID */
+ pid = fork();
+ if (pid == 0) {
+ ksft_print_msg("Child has PID %d\n", getpid());
+ usleep(500);
+ _exit(EXIT_SUCCESS);
+ }
+ (void)wait(NULL);
+ /* After the child has finished, its PID should be free. */
+ set_tid[0] = pid;
+ test_clone3_set_tid(set_tid, 1, 0, 0, 0, 0);
+ /* This should fail as there is no PID 1 in that namespace */
+ test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
+ set_tid[0] = 1;
+ set_tid[1] = pid;
+ test_clone3_set_tid(set_tid, 2, CLONE_NEWPID, 0, pid, 0);
+
+ ksft_print_msg("unshare PID namespace\n");
+ unshare(CLONE_NEWPID);
+ set_tid[0] = pid;
+ /* This should fail as there is no PID 1 in that namespace */
+ test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
+
+ /* Let's create a PID 1 */
+ ns_pid = fork();
+ if (ns_pid == 0) {
+ ksft_print_msg("Child in PID namespace has PID %d\n", getpid());
+ set_tid[0] = 2;
+ test_clone3_set_tid(set_tid, 1, 0, 0, 2, 0);
+ set_tid[0] = 1;
+ set_tid[1] = 42;
+ set_tid[2] = pid;
+ /*
+ * This should fail as there are not enough active PID
+ * namespaces. Again assuming this is running in the host's
+ * PID namespace. Not yet nested.
+ */
+ test_clone3_set_tid(set_tid, 4, CLONE_NEWPID, -EINVAL, 0, 0);
+ /*
+ * This should work and from the parent we should see
+ * something like 'NSpid: pid 42 1'.
+ */
+ test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, 0, 42, 1);
+ _exit(ksft_cnt.ksft_pass);
+ }
+
+ close(pipe_1[1]);
+ close(pipe_2[0]);
+ while (read(pipe_1[0], &buf, 1) > 0) {
+ ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
+ break;
+ }
+
+ asprintf(&proc, "/proc/%d/status", pid);
+ f = fopen(proc, "r");
+ if (f == NULL)
+ ksft_exit_fail_msg(
+ "%s - Could not open %s\n",
+ strerror(errno), proc);
+ while (fgets(line, 1024, f)) {
+ if (strstr(line, "NSpid")) {
+ /* Verify that all generated PIDs are as expected. */
+ sscanf(line, "NSpid:\t%d\t%d\t%d", &ns3, &ns2, &ns1);
+ break;
+ }
+ }
+ fclose(f);
+ free(proc);
+ close(pipe_2[0]);
+ /* Tell the clone3()'d child to finish. */
+ write(pipe_2[1], &buf, 1);
+ close(pipe_2[1]);
+
+ if (wait(&status) < 0) {
+ ksft_print_msg("Child returned %s\n", strerror(errno));
+ ret = -errno;
+ goto out;
+ }
+ if (WEXITSTATUS(status))
+ /*
+ * Update the number of total tests with the tests from the
+ * child processes.
+ */
+ ksft_cnt.ksft_pass = WEXITSTATUS(status);
+
+ if (ns3 == pid && ns2 == 42 && ns1 == 1)
+ ksft_test_result_pass(
+ "PIDs in all namespaces as expected (%d,%d,%d)\n",
+ ns3, ns2, ns1);
+ else
+ ksft_test_result_fail(
+ "PIDs in all namespaces not as expected (%d,%d,%d)\n",
+ ns3, ns2, ns1);
+out:
+ ret = 0;
+
+ return !ret ? ksft_exit_pass() : ksft_exit_fail();
+}
--
2.23.0
On Wed, Nov 13, 2019 at 09:03:00AM +0100, Adrian Reber wrote:
> The main motivation to add set_tid to clone3() is CRIU.
>
> To restore a process with the same PID/TID CRIU currently uses
> /proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to
> ns_last_pid and then (quickly) does a clone(). This works most of the
> time, but it is racy. It is also slow as it requires multiple syscalls.
>
> Extending clone3() to support *set_tid makes it possible restore a
> process using CRIU without accessing /proc/sys/kernel/ns_last_pid and
> race free (as long as the desired PID/TID is available).
>
> This clone3() extension places the same restrictions (CAP_SYS_ADMIN)
> on clone3() with *set_tid as they are currently in place for ns_last_pid.
>
> The original version of this change was using a single value for
> set_tid. At the 2019 LPC, after presenting set_tid, it was, however,
> decided to change set_tid to an array to enable setting the PID of a
> process in multiple PID namespaces at the same time. If a process is
> created in a PID namespace it is possible to influence the PID inside
> and outside of the PID namespace. Details also in the corresponding
> selftest.
>
> To create a process with the following PIDs:
>
> PID NS level Requested PID
> 0 (host) 31496
> 1 42
> 2 1
>
> For that example the two newly introduced parameters to struct
> clone_args (set_tid and set_tid_size) would need to be:
>
> set_tid[0] = 1;
> set_tid[1] = 42;
> set_tid[2] = 31496;
> set_tid_size = 3;
>
> If only the PIDs of the two innermost nested PID namespaces should be
> defined it would look like this:
>
> set_tid[0] = 1;
> set_tid[1] = 42;
> set_tid_size = 2;
>
> The PID of the newly created process would then be the next available
> free PID in the PID namespace level 0 (host) and 42 in the PID namespace
> at level 1 and the PID of the process in the innermost PID namespace
> would be 1.
>
> The set_tid array is used to specify the PID of a process starting
> from the innermost nested PID namespaces up to set_tid_size PID namespaces.
>
> set_tid_size cannot be larger then the current PID namespace level.
>
> Signed-off-by: Adrian Reber <[email protected]>
Adrian, when you resend, can you please add --base=<commit> with the
base commit this series applies to? This makes my life easier when
applying this series.
Other from missing kernel-doc (see below) I don't have any further
complaints atm.
> ---
> v2:
> - Removed (size < sizeof(struct clone_args)) as discussed with
> Christian and Dmitry
> - Added comment to ((set_tid != 1) && idr_get_cursor() <= 1) (Oleg)
> - Use idr_alloc() instead of idr_alloc_cyclic() (Oleg)
>
> v3:
> - Return EEXIST if PID is already in use (Christian)
> - Drop CLONE_SET_TID (Christian and Oleg)
> - Use idr_is_empty() instead of idr_get_cursor() (Oleg)
> - Handle different `struct clone_args` sizes (Dmitry)
>
> v4:
> - Rework struct size check with defines (Christian)
> - Reduce number of set_tid checks (Oleg)
> - Less parentheses and more robust code (Oleg)
> - Do ns_capable() on correct user_ns (Oleg, Christian)
>
> v5:
> - make set_tid checks earlier in alloc_pid() (Christian)
> - remove unnecessary comment and struct size check (Christian)
>
> v6:
> - remove CLONE_SET_TID from description (Christian)
> - add clone3() tests for different clone_args sizes (Christian)
> - move more set_tid checks to alloc_pid() (Oleg)
> - make all set_tid checks lockless (Oleg)
>
> v7:
> - changed set_tid to be an array to set the PID of a process
> in multiple nested PID namespaces at the same time as discussed
> at LPC 2019 (container MC)
>
> v8:
> - skip unnecessary memset() (Rasmus)
> - replace set_tid copy loop with a single copy (Christian)
> - more parameter error checking (Christian)
> - cache set_tid in alloc_pid() (Oleg)
> - move code in "else" branch (Oleg)
> ---
> include/linux/pid.h | 3 +-
> include/linux/pid_namespace.h | 2 ++
> include/linux/sched/task.h | 3 ++
> include/uapi/linux/sched.h | 2 ++
> kernel/fork.c | 24 ++++++++++++-
> kernel/pid.c | 64 +++++++++++++++++++++++++++--------
> kernel/pid_namespace.c | 2 --
> 7 files changed, 82 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/pid.h b/include/linux/pid.h
> index 9645b1194c98..034b7df25888 100644
> --- a/include/linux/pid.h
> +++ b/include/linux/pid.h
> @@ -120,7 +120,8 @@ extern struct pid *find_vpid(int nr);
> extern struct pid *find_get_pid(int nr);
> extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
>
> -extern struct pid *alloc_pid(struct pid_namespace *ns);
> +extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
> + size_t set_tid_size);
> extern void free_pid(struct pid *pid);
> extern void disable_pid_allocation(struct pid_namespace *ns);
>
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index 49538b172483..2ed6af88794b 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -12,6 +12,8 @@
> #include <linux/ns_common.h>
> #include <linux/idr.h>
>
> +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> +#define MAX_PID_NS_LEVEL 32
>
> struct fs_pin;
>
> diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
> index 4b1c3b664f51..f1879884238e 100644
> --- a/include/linux/sched/task.h
> +++ b/include/linux/sched/task.h
> @@ -26,6 +26,9 @@ struct kernel_clone_args {
> unsigned long stack;
> unsigned long stack_size;
> unsigned long tls;
> + pid_t *set_tid;
> + /* Number of elements in *set_tid */
> + size_t set_tid_size;
> };
>
> /*
> diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
> index 25b4fa00bad1..13f74c40a629 100644
> --- a/include/uapi/linux/sched.h
> +++ b/include/uapi/linux/sched.h
> @@ -72,6 +72,8 @@ struct clone_args {
> __aligned_u64 stack;
> __aligned_u64 stack_size;
> __aligned_u64 tls;
> + __aligned_u64 set_tid;
> + __aligned_u64 set_tid_size;
Please add kernel-doc comments for these two new fields to the top of
the like we did for all the other fields.
Christian
On Wed, Nov 13, 2019 at 09:03:01AM +0100, Adrian Reber wrote:
> This tests clone3() with *set_tid to see if all desired PIDs are working
> as expected. The tests are trying multiple invalid input parameters as
> well as creating processes while specifying a certain PID in multiple
> PID namespaces at the same time.
>
> Signed-off-by: Adrian Reber <[email protected]>
> ---
> tools/testing/selftests/clone3/.gitignore | 1 +
> tools/testing/selftests/clone3/Makefile | 2 +-
> .../testing/selftests/clone3/clone3_set_tid.c | 345 ++++++++++++++++++
> 3 files changed, 347 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/clone3/clone3_set_tid.c
>
> diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore
> index 85d9d3ba2524..d56c3c49d869 100644
> --- a/tools/testing/selftests/clone3/.gitignore
> +++ b/tools/testing/selftests/clone3/.gitignore
> @@ -1 +1,2 @@
> clone3
> +clone3_set_tid
> diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
> index ea922c014ae4..2d292545ca8e 100644
> --- a/tools/testing/selftests/clone3/Makefile
> +++ b/tools/testing/selftests/clone3/Makefile
> @@ -2,6 +2,6 @@
>
> CFLAGS += -I../../../../usr/include/
>
> -TEST_GEN_PROGS := clone3
> +TEST_GEN_PROGS := clone3 clone3_set_tid
Another example, where --base would help me out. :) (Since I can already
see that this is missing the clone3_clear_sighand test that's scheduled
for 5.5. :))
>
> include ../lib.mk
> diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c b/tools/testing/selftests/clone3/clone3_set_tid.c
> new file mode 100644
> index 000000000000..9a234fd2031e
> --- /dev/null
> +++ b/tools/testing/selftests/clone3/clone3_set_tid.c
> @@ -0,0 +1,345 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Based on Christian Brauner's clone3() example.
> + * These tests are assuming to be running in the host's
> + * PID namespace.
> + */
> +
> +#define _GNU_SOURCE
> +#include <errno.h>
> +#include <linux/types.h>
> +#include <linux/sched.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/syscall.h>
> +#include <sys/types.h>
> +#include <sys/un.h>
> +#include <sys/wait.h>
> +#include <unistd.h>
> +#include <sched.h>
> +
> +#include "../kselftest.h"
> +
> +#ifndef MAX_PID_NS_LEVEL
> +#define MAX_PID_NS_LEVEL 32
> +#endif
> +
> +static int pipe_1[2];
> +static int pipe_2[2];
> +
> +static pid_t raw_clone(struct clone_args *args)
> +{
> + return syscall(__NR_clone3, args, sizeof(struct clone_args));
> +}
So that function is now present in the clone3.c test you've added and
also in the clone3_clear_sighand.c under sys_clone3().
If you take [1] as your base tree you could add patches that consolidate
this definition into a header so we avoid the pointless code
duplication.
(Again, if you pass --base when doing --format-patch this will be
transparent to others.)
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=pidfd
> +
> +static int call_clone3_set_tid(pid_t *set_tid,
> + size_t set_tid_size,
> + int flags,
> + int expected_pid,
> + int wait_for_it)
Nit: Why is that an int and not a bool? :)
> +{
> + int status;
> + int ret = 0;
> + pid_t pid = -1;
> + struct clone_args args = {0};
> +
> + args.flags = flags;
> + args.exit_signal = SIGCHLD;
> + args.set_tid = (__u64)set_tid;
> + args.set_tid_size = set_tid_size;
Nit: You can save the {0} by just doing:
struct clone_args args = {
.flags = flags,
.exit_signal = SIGCHLD,
.set_tid = (__u64)set_tid,
.set_tid_size = set_tid_size,
};
Also, I'd prefer if the cast would be done "properly" via
#define ptr_to_u64(ptr) ((__u64)((uintptr_t)(ptr)))
struct clone_args args = {
.flags = flags,
.exit_signal = SIGCHLD,
.set_tid = ptr_to_u64(set_tid),
.set_tid_size = set_tid_size,
};
> +
> + pid = raw_clone(&args);
> + if (pid < 0) {
> + ksft_print_msg("%s - Failed to create new process\n",
> + strerror(errno));
> + return -errno;
> + }
> +
> + if (pid == 0) {
> + char tmp = 0;
> + ksft_print_msg("I am the child, my PID is %d (expected %d)\n",
> + getpid(), set_tid[0]);
> + if (wait_for_it) {
> + ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
> + /* Signal the parent that the child is ready */
> + close(pipe_1[0]);
> + write(pipe_1[1], &tmp, 1);
> + close(pipe_1[1]);
> + close(pipe_2[1]);
> + read(pipe_2[0], &tmp, 1);
> + close(pipe_2[0]);
> + }
> +
> + if (set_tid[0] != getpid())
> + _exit(EXIT_FAILURE);
> + _exit(EXIT_SUCCESS);
> + }
> +
> + if (expected_pid == 0 || expected_pid == pid)
> + ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
> + getpid(), pid);
> + else {
If one branch needs {} all branches should have {} according to kernel
coding style.
> + ksft_print_msg(
> + "Expected child pid %d does not match actual pid %d\n",
> + expected_pid, pid);
> + ret = -1;
> + }
> +
> + if (wait(&status) < 0) {
> + ksft_print_msg("Child returned %s\n", strerror(errno));
> + return -errno;
> + }
> + if (WEXITSTATUS(status))
> + return WEXITSTATUS(status);
You should probably rather check:
if (!WIFEXITED(status))
return -1;
return WEXITSTATUS(status));
Since you can also get killed by a signal.
> +
> + return ret;
> +}
> +
> +static void test_clone3_set_tid(pid_t *set_tid,
> + size_t set_tid_size,
> + int flags,
> + int expected,
> + int expected_pid,
> + int wait_for_it)
> +{
> + int ret;
> +
> + ksft_print_msg(
> + "[%d] Trying clone3() with CLONE_SET_TID to %d and 0x%x\n",
> + getpid(), set_tid[0], flags);
> + ret = call_clone3_set_tid(set_tid, set_tid_size, flags, expected_pid,
> + wait_for_it);
> + ksft_print_msg(
> + "[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n",
> + getpid(), set_tid[0], ret, expected);
> + if (ret != expected)
> + ksft_test_result_fail(
> + "[%d] Result (%d) is different than expected (%d)\n",
> + getpid(), ret, expected);
> + else
> + ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n",
> + getpid(), ret, expected);
> +}
> +int main(int argc, char *argv[])
> +{
> + FILE *f;
> + char buf;
> + pid_t pid;
> + pid_t ns1;
> + pid_t ns2;
> + pid_t ns3;
Nit:
pid_t pid, ns1, ns2, ns3, ns_pid;
> + int status;
> + char *proc;
> + int ret = -1;
> + pid_t ns_pid;
> + int pid_max = 0;
> + uid_t uid = getuid();
> + char line[1024] = {0};
> + pid_t set_tid[MAX_PID_NS_LEVEL * 2];
> + pid_t set_tid_small[1];
> +
> + if (pipe(pipe_1) == -1 || pipe(pipe_2))
> + ksft_exit_fail_msg("pipe() failed\n");
Nit: The error checking here is inconsistent. Either do:
if (pipe(pipe_1) || pipe(pipe_2))
ksft_exit_fail_msg("pipe() failed\n");
or
if (pipe(pipe_1) < 0 || pipe(pipe_2) < 0)
ksft_exit_fail_msg("pipe() failed\n");
or == -1 but not mixed, please. :)
> +
> + ksft_print_header();
> + ksft_set_plan(27);
Now that's ambitious testing. I like it. :)
> +
> + f = fopen("/proc/sys/kernel/pid_max", "r");
> + if (f == NULL)
> + ksft_exit_fail_msg(
> + "%s - Could not open /proc/sys/kernel/pid_max\n",
> + strerror(errno));
> + fscanf(f, "%d", &pid_max);
> + fclose(f);
> + ksft_print_msg("/proc/sys/kernel/pid_max %d\n", pid_max);
> +
> + /* Try invalid settings */
> + memset(&set_tid, 0, sizeof(set_tid));
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -E2BIG, 0, 0);
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -E2BIG, 0, 0);
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0, -E2BIG, 0, 0);
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -E2BIG, 0, 0);
> +
> + /* small set_tid array, but maximum set_tid_size */
> + /* Find the current active PID */
> + pid = fork();
> + if (pid == 0) {
> + ksft_print_msg("Child has PID %d\n", getpid());
> + _exit(EXIT_SUCCESS);
> + }
> + (void)wait(NULL);
> + /* After the child has finished, its PID should be free. */
> + set_tid_small[0] = pid;
> + /*
> + * There is a chance that this can return -EFAULT as the actual
> + * set_tid array has only one entry, but we are telling the kernel
> + * that it has the size MAX_PID_NS_LEVEL. This could lead to a
> + * situation where copy_from_user() fails. So far it always
> + * succeeds and copies random data (whatever is after set_tid_small).
> + */
> + test_clone3_set_tid(set_tid_small, MAX_PID_NS_LEVEL, 0, -EINVAL, 0, 0);
Hm, I'm not sure that test makes a lot of sense.
> +
> + /*
> + * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
> + * nested PID namespace.
> + */
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
> +
> + memset(&set_tid, 0xff, sizeof(set_tid));
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL + 1, 0, -E2BIG, 0, 0);
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2, 0, -E2BIG, 0, 0);
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 2 + 1, 0, -E2BIG, 0, 0);
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL * 42, 0, -E2BIG, 0, 0);
> + /*
> + * This can actually work if this test running in a MAX_PID_NS_LEVEL - 1
> + * nested PID namespace.
> + */
> + test_clone3_set_tid(set_tid, MAX_PID_NS_LEVEL - 1, 0, -EINVAL, 0, 0);
> +
> + memset(&set_tid, 0, sizeof(set_tid));
> + /* Try with an invalid PID */
> + set_tid[0] = 0;
> + test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
> + set_tid[0] = -1;
> + test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
> + /* Claim that the set_tid array actually contains 2 elements. */
> + test_clone3_set_tid(set_tid, 2, 0, -EINVAL, 0, 0);
> + /* Try it in a new PID namespace */
> + if (uid == 0)
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
> + else
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
[1]:
I mean, you could really just do
if (uid == 0)
test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
the else branch doesn't really test anything meaningful other than you
can't create new pid namespaces as an unprivileged user without also
creating a new user namespace.
> +
> + /*
> + * Try with a valid PID (1) but as non-root. This should fail
> + * with -EPERM if running in the initial user namespace.
> + * As root it should tell us -EEXIST.
> + */
> + set_tid[0] = 1;
> + if (uid == 0)
> + test_clone3_set_tid(set_tid, 1, 0, -EEXIST, 0, 0);
> + else
> + test_clone3_set_tid(set_tid, 1, 0, -EPERM, 0, 0);
See [1].
> +
> + /* Try it in a new PID namespace */
> + if (uid == 0)
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, 0, 0, 0);
> + else
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
See [1].
> +
> + /* pid_max should fail everywhere */
> + set_tid[0] = pid_max;
> + test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
> + if (uid == 0)
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
> + else
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EPERM, 0, 0);
See [1].
> +
> + if (uid != 0) {
> + /*
> + * All remaining tests require root. Tell the framework
> + * that all those tests are skipped as non-root.
> + */
> + ksft_cnt.ksft_xskip += ksft_plan - ksft_test_num();
> + goto out;
> + }
> +
> + /* Find the current active PID */
> + pid = fork();
> + if (pid == 0) {
> + ksft_print_msg("Child has PID %d\n", getpid());
> + usleep(500);
Why the usleep(500)?
> + _exit(EXIT_SUCCESS);
> + }
> + (void)wait(NULL);
\n
> + /* After the child has finished, its PID should be free. */
> + set_tid[0] = pid;
> + test_clone3_set_tid(set_tid, 1, 0, 0, 0, 0);
\n
> + /* This should fail as there is no PID 1 in that namespace */
> + test_clone3_set_tid(set_tid, 1, CLONE_NEWPID, -EINVAL, 0, 0);
Nit: please add \n between a two tests everywhere, especially if they
have comments on top of it. This is a little hard to read. :)
> + set_tid[0] = 1;
> + set_tid[1] = pid;
> + test_clone3_set_tid(set_tid, 2, CLONE_NEWPID, 0, pid, 0);
This is missing a comment.
> +
> + ksft_print_msg("unshare PID namespace\n");
> + unshare(CLONE_NEWPID);
Why no error checking here when the next line assumes that there is no
PID 1 in that namespace?
> + set_tid[0] = pid;
> + /* This should fail as there is no PID 1 in that namespace */
> + test_clone3_set_tid(set_tid, 1, 0, -EINVAL, 0, 0);
> +
> + /* Let's create a PID 1 */
> + ns_pid = fork();
> + if (ns_pid == 0) {
> + ksft_print_msg("Child in PID namespace has PID %d\n", getpid());
> + set_tid[0] = 2;
> + test_clone3_set_tid(set_tid, 1, 0, 0, 2, 0);
> + set_tid[0] = 1;
> + set_tid[1] = 42;
> + set_tid[2] = pid;
> + /*
> + * This should fail as there are not enough active PID
> + * namespaces. Again assuming this is running in the host's
> + * PID namespace. Not yet nested.
> + */
> + test_clone3_set_tid(set_tid, 4, CLONE_NEWPID, -EINVAL, 0, 0);
> + /*
> + * This should work and from the parent we should see
> + * something like 'NSpid: pid 42 1'.
[2]:
You could verify this...
In tools/testing/selftests/pidfd/pidfd_fdinfo_test.c in my pidfd tree
is code that does this. You could just copy it. Look for
verify_fdinfo(). Though, I'll it for you to judge whether this is too
much hazzle.
> + */
> + test_clone3_set_tid(set_tid, 3, CLONE_NEWPID, 0, 42, 1);
> + _exit(ksft_cnt.ksft_pass);
Again, the missing \n makes the different tests hard to follow.
> + }
> +
> + close(pipe_1[1]);
> + close(pipe_2[0]);
> + while (read(pipe_1[0], &buf, 1) > 0) {
> + ksft_print_msg("[%d] Child is ready and waiting\n", getpid());
> + break;
> + }
> +
> + asprintf(&proc, "/proc/%d/status", pid);
char proc_path[100];
snprintf(proc_path, sizeof(proc_path), "/proc/%d/status", pid);
should do just fine and doesn't require you to free memory.
> + f = fopen(proc, "r");
> + if (f == NULL)
> + ksft_exit_fail_msg(
> + "%s - Could not open %s\n",
> + strerror(errno), proc);
> + while (fgets(line, 1024, f)) {
Ugh, fgets... :) I'd feel much happier with getline().
> + if (strstr(line, "NSpid")) {
> + /* Verify that all generated PIDs are as expected. */
> + sscanf(line, "NSpid:\t%d\t%d\t%d", &ns3, &ns2, &ns1);
> + break;
Oh this is the verification code for fdinfo, I mentioned in [2]. Again,
maybe you want to copy verify_fdinfo() and move this into a helper.
> + }
> + }
> + fclose(f);
> + free(proc);
> + close(pipe_2[0]);
\n
> + /* Tell the clone3()'d child to finish. */
> + write(pipe_2[1], &buf, 1);
> + close(pipe_2[1]);
> +
> + if (wait(&status) < 0) {
> + ksft_print_msg("Child returned %s\n", strerror(errno));
> + ret = -errno;
> + goto out;
> + }
> + if (WEXITSTATUS(status))
Nit: This should probably also verify if (WIFEXITED(status)).
On 11/13, Adrian Reber wrote:
>
> @@ -175,23 +187,47 @@ struct pid *alloc_pid(struct pid_namespace *ns)
>
> for (i = ns->level; i >= 0; i--) {
> int pid_min = 1;
Well, this is really minor but again, pid_min is only used in the "else"
branch below, you can move this declaration there.
> +
> + if (set_tid_size) {
> + tid = set_tid[ns->level - i];
> + if (tid < 1 || tid >= pid_max)
> + return ERR_PTR(-EINVAL);
> + /* Also fail if a PID != 1 is requested and no PID 1 exists */
> + if (tid != 1 && !tmp->child_reaper)
> + return ERR_PTR(-EINVAL);
> + if (!ns_capable(tmp->user_ns, CAP_SYS_ADMIN))
> + return ERR_PTR(-EPERM);
> + }
>
> idr_preload(GFP_KERNEL);
> spin_lock_irq(&pidmap_lock);
>
> - /*
> - * init really needs pid 1, but after reaching the maximum
> - * wrap back to RESERVED_PIDS
> - */
> - if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
> - pid_min = RESERVED_PIDS;
> -
> - /*
> - * Store a null pointer so find_pid_ns does not find
> - * a partially initialized PID (see below).
> - */
> - nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
> - pid_max, GFP_ATOMIC);
> + if (tid) {
> + nr = idr_alloc(&tmp->idr, NULL, tid,
> + tid + 1, GFP_ATOMIC);
> + /*
> + * If ENOSPC is returned it means that the PID is
> + * alreay in use. Return EEXIST in that case.
> + */
> + if (nr == -ENOSPC)
> + nr = -EEXIST;
> + set_tid_size--;
^^^^^^^^^^^^^^^
May I ask you to move this decrement into the "if (set_tid_size)" block above?
Oleg.