The change I put into copy_thread() just papered over the real
problem.
When we are looking to see if we should do a syscall restart, when
deliverying a signal, we should only interpret the syscall return
value as an error if the carry condition code(s) are set.
Otherwise it's a success return.
Also, sigreturn paths should do a pt_regs_clear_trap_type().
It turns out that doing a syscall restart when returning from a fork()
does and should happen, from time to time. Even if copy_thread()
returns success, copy_process() can still unwind and signal
-ERESTARTNOINTR in the parent.
Signed-off-by: David S. Miller <davem@davemloft.net>
2678fefedb