s390/signal: Fix incorrect return address in signal frame

exit_to_user_mode_loop() can call arch_do_signal_or_restart() multiple
times when signals are pending.

If the first call set up a vDSO system call restart by saving the real
user return address and adjusting psw.addr so it points to the vDSO stub,
a second call builds the signal frame with the wrong return address.

Restore psw.addr from arch_data, and set the return code to -EINTR before
building the signal frame.

This requires restart_block.arch_data to be properly initialized for all
tasks. Move the initialization in copy_thread() in front of the kernel
thread check, so that it also covers kernel threads and their children
(PID 1, usermode helpers). Only PID 0 is left uninitialized, since it
never returns to user space.

Fixes: df29a7440c4b ("s390/signal: switch to using vdso for sigreturn and syscall restart")
Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions