Re: [Qemu-devel] [PATCH 1/4] linux-user: Disallow setting newsp for fork

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> Or really, just clone devolving into fork.  This should not ever happen
> in practice.  We do want to reserve calling cpu_clone_regs for the case
> in which we are actually performing a clone.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  linux-user/syscall.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index dfc851cc35..5bf8d13de7 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -6502,10 +6502,14 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
>          pthread_mutex_destroy(&info.mutex);
>          pthread_mutex_unlock(&clone_lock);
>      } else {
> -        /* if no CLONE_VM, we consider it is a fork */
> +        /* If no CLONE_VM, we consider it is a fork.  */
>          if (flags & CLONE_INVALID_FORK_FLAGS) {
>              return -TARGET_EINVAL;
>          }
> +        /* As a fork, setting a new sp does not make sense.  */
> +        if (newsp) {
> +            return -TARGET_EINVAL;
> +        }
>
>          /* We can't support custom termination signals */
>          if ((flags & CSIGNAL) != TARGET_SIGCHLD) {
> @@ -6520,7 +6524,6 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
>          ret = fork();
>          if (ret == 0) {
>              /* Child Process.  */
> -            cpu_clone_regs(env, newsp);
>              fork_end(1);
>              /* There is a race condition here.  The parent process could
>                 theoretically read the TID in the child process before the child


--
Alex Bennée