s390/signal: fix endless loop in do_signal

stable inclusion
from stable-v5.10.169
commit 645df4047bd67e368c5fe9783a115916c4128c1d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7V9QX

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=645df4047bd67e368c5fe9783a115916c4128c1d



----------------------------------------------------

No upstream commit exists: the problem addressed here is that 'commit
75309018 ("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 56e62a73
("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: 75309018 ("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>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>