Commit fc66127d authored Jun 11, 2021 by Sven Schnelle Committed by Vasily Gorbik Jun 21, 2021

s390: fix system call restart with multiple signals



glibc complained with "The futex facility returned an unexpected error
code.". It turned out that the futex syscall returned -ERESTARTSYS because
a signal is pending. arch_do_signal_or_restart() restored the syscall
parameters (nameley regs->gprs[2]) and set PIF_SYSCALL_RESTART. When
another signal is made pending later in the exit loop
arch_do_signal_or_restart() is called again. This function clears
PIF_SYSCALL_RESTART and checks the return code which is set in
regs->gprs[2]. However, regs->gprs[2] was restored in the previous run
and no longer contains -ERESTARTSYS, so PIF_SYSCALL_RESTART isn't set
again and the syscall is skipped.

Fix this by not clearing PIF_SYSCALL_RESTART - it is already cleared in
__do_syscall() when the syscall is restarted.

Reported-by: Bjoern Walk <bwalk@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Fixes: 56e62a73 ("s390: convert to generic entry")
Cc: <stable@vger.kernel.org> # 5.12
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

parent 13311e74

arch/s390/kernel/signal.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -512,7 +512,6 @@ void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)

		/* No handlers present - check for system call restart */
		clear_pt_regs_flag(regs, PIF_SYSCALL);
		clear_pt_regs_flag(regs, PIF_SYSCALL_RESTART);
		if (current->thread.system_call) {
		regs->int_code = current->thread.system_call;
		switch (regs->gprs[2]) {