From: Sumanth Korikkar sumanthk@linux.ibm.com
No upstream commit exists: the problem addressed here is that 'commit 75309018a24d ("s390: add support for TIF_NOTIFY_SIGNAL")' was backported to 5.10. This commit is broken, but nobody noticed upstream, since shortly after s390 converted to generic entry with 'commit 56e62a737028 ("s390: convert to generic entry")', which implicitly fixed the problem outlined below.
Thread flag is set to TIF_NOTIFY_SIGNAL for io_uring work. The io work user or syscall calls do_signal when either one of the TIF_SIGPENDING or TIF_NOTIFY_SIGNAL flag is set. However, do_signal does consider only TIF_SIGPENDING signal and ignores TIF_NOTIFY_SIGNAL condition. This means get_signal is never invoked for TIF_NOTIFY_SIGNAL and hence the flag is not cleared, which results in an endless do_signal loop.
Reference: 'commit 788d0824269b ("io_uring: import 5.15-stable io_uring")' Fixes: 75309018a24d ("s390: add support for TIF_NOTIFY_SIGNAL") Cc: stable@vger.kernel.org # 5.10.162 Acked-by: Heiko Carstens hca@linux.ibm.com Acked-by: Sven Schnelle svens@linux.ibm.com Signed-off-by: Sumanth Korikkar sumanthk@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/s390/kernel/signal.c +++ b/arch/s390/kernel/signal.c @@ -472,7 +472,7 @@ void do_signal(struct pt_regs *regs) current->thread.system_call = test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;
- if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) { + if (get_signal(&ksig)) { /* Whee! Actually deliver the signal. */ if (current->thread.system_call) { regs->int_code = current->thread.system_call;