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Sven Schnelle authored
with generic entry, there's a bug when it comes to restarting of signals. The failing sequence is: a) a signal is coming in, and no handler is registered, so the lower part of arch_do_signal_or_restart() in arch/s390/kernel/signal.c sets PIF_SYSCALL_RESTART. b) a second signal gets pending while the kernel is still in the exit loop, and for that one, a handler exists. c) The first part of arch_do_signal_or_restart() is called. That part calls handle_signal(), which sets up stack + registers for handling the signal. d) __do_syscall() in arch/s390/kernel/syscall.c checks for PIF_SYSCALL_RESTART right before leaving to userspace. If it is set, it restart's the syscall. However, the registers are already setup for handling a signal from c). The syscall is now restarted with the wrong arguments. Change the code to: - use vdso for syscall_restart() instead of PIF_SYSCALL_RESTART because we cannot rewind and go back to userspace on s390 because the system call number might be encoded in the svc instruction. - for all other syscalls we rewind the PSW and return to userspace. Cc: <stable@kernel.org> # v5.12+ d57778fe: s390/vdso: always enable vdso Cc: <stable@kernel.org> # v5.12+ 686341f2: s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall Cc: <stable@kernel.org> # v5.12+ 43e1f76b: s390/vdso: rename VDSO64_LBASE to VDSO_LBASE Cc: <stable@kernel.org> # v5.12+ 779df224: s390/vdso: add minimal compat vdso Cc: <stable@kernel.org> # v5.12+ Signed-off-by:
Sven Schnelle <svens@linux.ibm.com> Reviewed-by:
Heiko Carstens <hca@linux.ibm.com> Signed-off-by:
Vasily Gorbik <gor@linux.ibm.com>
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