"Dmitry V. Levin" <ldv@xxxxxxxxxxxx> writes:
> On sparc, fork and clone syscalls have an unusual semantics of
> returning the pid of the parent process to the child process.
>
> Apparently, the implementation did not honor pid namespaces at all,
> so the child used to get the pid of its parent in the init namespace.
>
> Fortunately, most users of these syscalls are not affected by this bug
> because they use another register to distinguish the parent process
> from its child, and the pid of the parent process is often discarded.
>
> Reproducer:
>
> $ gcc -Wall -O2 -xc - <<'EOF'
> #define _GNU_SOURCE
> #include <err.h>
> #include <errno.h>
> #include <sched.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/wait.h>
> #include <unistd.h>
> #include <asm/unistd.h>
> #include <linux/sched.h>
> static void test_fork(void)
> {
> int pid = syscall(__NR_fork);
> if (pid < 0)
> err(1, "fork");
> fprintf(stderr, "current: %d, parent: %d, fork returned: %d\n",
> getpid(), getppid(), pid);
> int status;
> if (wait(&status) < 0) {
> if (errno == ECHILD)
> _exit(0);
> err(1, "wait");
> }
> if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
> errx(1, "wait: %#x", status);
> }
> int main(void)
> {
> test_fork();
> if (unshare(CLONE_NEWPID | CLONE_NEWUSER) < 0)
> err(1, "unshare");
> test_fork();
> return 0;
> }
> EOF
> $ sh -c ./a.out
> current: 10001, parent: 10000, fork returned: 10002
> current: 10002, parent: 10001, fork returned: 10001
> current: 10001, parent: 10000, fork returned: 10003
> current: 1, parent: 0, fork returned: 10001
>
> This bug was found by strace test suite.
>
> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
> ---
>
> v2: Replaced task_active_pid_ns(p) with current->nsproxy->pid_ns_for_children
> as suggested by Eric.
I can't test this either. But from just reading through the code earlier.
Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> arch/sparc/kernel/process_32.c | 3 ++-
> arch/sparc/kernel/process_64.c | 3 ++-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
> index a02363735915..3be653e40204 100644
> --- a/arch/sparc/kernel/process_32.c
> +++ b/arch/sparc/kernel/process_32.c
> @@ -368,7 +368,8 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
> #endif
>
> /* Set the return value for the child. */
> - childregs->u_regs[UREG_I0] = current->pid;
> + childregs->u_regs[UREG_I0] =
> + task_pid_nr_ns(current, current->nsproxy->pid_ns_for_children);
> childregs->u_regs[UREG_I1] = 1;
>
> /* Set the return value for the parent. */
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index 6f8c7822fc06..f53ef5cff46a 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -629,7 +629,8 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
> t->utraps[0]++;
>
> /* Set the return value for the child. */
> - t->kregs->u_regs[UREG_I0] = current->pid;
> + t->kregs->u_regs[UREG_I0] =
> + task_pid_nr_ns(current, current->nsproxy->pid_ns_for_children);
> t->kregs->u_regs[UREG_I1] = 1;
>
> /* Set the second return value for the parent. */
