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s390: fix system call restart with multiple signals

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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: 56e62a737028 ("s390: convert to generic entry")
Cc: <stable@vger.kernel.org> # 5.12
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Sven Schnelle 2021-06-11 10:27:51 +02:00 committed by Vasily Gorbik
parent 13311e7425
commit fc66127dc3
1 changed files with 0 additions and 1 deletions
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arch/s390/kernel/signal.c
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@ -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]) {