From df29a7440c4b5c65765c8f60396b3b13063e24e9 Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Fri, 25 Jun 2021 15:02:08 +0200 Subject: s390/signal: switch to using vdso for sigreturn and syscall restart 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: # v5.12+ d57778feb987: s390/vdso: always enable vdso Cc: # v5.12+ 686341f2548b: s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall Cc: # v5.12+ 43e1f76b0b69: s390/vdso: rename VDSO64_LBASE to VDSO_LBASE Cc: # v5.12+ 779df2248739: s390/vdso: add minimal compat vdso Cc: # v5.12+ Signed-off-by: Sven Schnelle Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/kernel/process.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/s390/kernel/process.c') diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c index 7ae5dde9c54d..350e94d0cac2 100644 --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -166,6 +166,12 @@ int copy_thread(unsigned long clone_flags, unsigned long new_stackp, p->thread.acrs[1] = (unsigned int)tls; } } + /* + * s390 stores the svc return address in arch_data when calling + * sigreturn()/restart_syscall() via vdso. 1 means no valid address + * stored. + */ + p->restart_block.arch_data = 1; return 0; } -- cgit v1.2.3