Merge tag 'execve-v6.0-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull execve reverts from Kees Cook:
 "The recent work to support time namespace unsharing turns out to have
  some undesirable corner cases, so rather than allowing the API to stay
  exposed for another release, it'd be best to remove it ASAP, with the
  replacement getting another cycle of testing. Nothing is known to use
  this yet, so no userspace breakage is expected.

  For more details, see:

    https://lore.kernel.org/lkml/ed418e43ad28b8688cfea2b7c90fce1c@ispras.ru

  Summary:

   - Remove the recent 'unshare time namespace on vfork+exec' feature
     (Andrei Vagin)"

* tag 'execve-v6.0-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  Revert "fs/exec: allow to unshare a time namespace on vfork+exec"
  Revert "selftests/timens: add a test for vfork+exit"

fs/exec.c

@@ -65,7 +65,6 @@
 #include <linux/io_uring.h>
 #include <linux/syscall_user_dispatch.h>
 #include <linux/coredump.h>
-#include <linux/time_namespace.h>
 
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
@@ -979,12 +978,10 @@ static int exec_mmap(struct mm_struct *mm)
 {
 	struct task_struct *tsk;
 	struct mm_struct *old_mm, *active_mm;
-	bool vfork;
 	int ret;
 
 	/* Notify parent that we're no longer interested in the old VM */
 	tsk = current;
-	vfork = !!tsk->vfork_done;
 	old_mm = current->mm;
 	exec_mm_release(tsk, old_mm);
 	if (old_mm)
@@ -1029,10 +1026,6 @@ static int exec_mmap(struct mm_struct *mm)
 	tsk->mm->vmacache_seqnum = 0;
 	vmacache_flush(tsk);
 	task_unlock(tsk);
-
-	if (vfork)
-		timens_on_fork(tsk->nsproxy, tsk);
-
 	if (old_mm) {
 		mmap_read_unlock(old_mm);
 		BUG_ON(active_mm != old_mm);

kernel/fork.c

@@ -2047,11 +2047,8 @@ static __latent_entropy struct task_struct *copy_process(
 	/*
 	 * If the new process will be in a different time namespace
 	 * do not allow it to share VM or a thread group with the forking task.
-	 *
-	 * On vfork, the child process enters the target time namespace only
-	 * after exec.
 	 */
-	if ((clone_flags & (CLONE_VM | CLONE_VFORK)) == CLONE_VM) {
+	if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
 		if (nsp->time_ns != nsp->time_ns_for_children)
 			return ERR_PTR(-EINVAL);
 	}

kernel/nsproxy.c

@@ -179,8 +179,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 	if (IS_ERR(new_ns))
 		return  PTR_ERR(new_ns);
 
-	if ((flags & CLONE_VM) == 0)
-		timens_on_fork(new_ns, tsk);
+	timens_on_fork(new_ns, tsk);
 
 	tsk->nsproxy = new_ns;
 	return 0;

tools/testing/selftests/timens/Makefile

-TEST_GEN_PROGS := timens timerfd timer clock_nanosleep procfs exec futex vfork_exec
+TEST_GEN_PROGS := timens timerfd timer clock_nanosleep procfs exec futex
 TEST_GEN_PROGS_EXTENDED := gettime_perf
 
 CFLAGS := -Wall -Werror -pthread

tools/testing/selftests/timens/vfork_exec.c

-// SPDX-License-Identifier: GPL-2.0
-#define _GNU_SOURCE
-#include <errno.h>
-#include <fcntl.h>
-#include <sched.h>
-#include <stdio.h>
-#include <stdbool.h>
-#include <sys/stat.h>
-#include <sys/syscall.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <time.h>
-#include <unistd.h>
-#include <string.h>
-
-#include "log.h"
-#include "timens.h"
-
-#define OFFSET (36000)
-
-int main(int argc, char *argv[])
-{
-	struct timespec now, tst;
-	int status, i;
-	pid_t pid;
-
-	if (argc > 1) {
-		if (sscanf(argv[1], "%ld", &now.tv_sec) != 1)
-			return pr_perror("sscanf");
-
-		for (i = 0; i < 2; i++) {
-			_gettime(CLOCK_MONOTONIC, &tst, i);
-			if (abs(tst.tv_sec - now.tv_sec) > 5)
-				return pr_fail("%ld %ld\n", now.tv_sec, tst.tv_sec);
-		}
-		return 0;
-	}
-
-	nscheck();
-
-	ksft_set_plan(1);
-
-	clock_gettime(CLOCK_MONOTONIC, &now);
-
-	if (unshare_timens())
-		return 1;
-
-	if (_settime(CLOCK_MONOTONIC, OFFSET))
-		return 1;
-
-	for (i = 0; i < 2; i++) {
-		_gettime(CLOCK_MONOTONIC, &tst, i);
-		if (abs(tst.tv_sec - now.tv_sec) > 5)
-			return pr_fail("%ld %ld\n",
-					now.tv_sec, tst.tv_sec);
-	}
-
-	pid = vfork();
-	if (pid < 0)
-		return pr_perror("fork");
-
-	if (pid == 0) {
-		char now_str[64];
-		char *cargv[] = {"exec", now_str, NULL};
-		char *cenv[] = {NULL};
-
-		// Check that we are still in the source timens.
-		for (i = 0; i < 2; i++) {
-			_gettime(CLOCK_MONOTONIC, &tst, i);
-			if (abs(tst.tv_sec - now.tv_sec) > 5)
-				return pr_fail("%ld %ld\n",
-						now.tv_sec, tst.tv_sec);
-		}
-
-		/* Check for proper vvar offsets after execve. */
-		snprintf(now_str, sizeof(now_str), "%ld", now.tv_sec + OFFSET);
-		execve("/proc/self/exe", cargv, cenv);
-		return pr_perror("execve");
-	}
-
-	if (waitpid(pid, &status, 0) != pid)
-		return pr_perror("waitpid");
-
-	if (status)
-		ksft_exit_fail();
-
-	ksft_test_result_pass("exec\n");
-	ksft_exit_pass();
-	return 0;
-}