The patch below does not apply to the 5.13-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From df29a7440c4b5c65765c8f60396b3b13063e24e9 Mon Sep 17 00:00:00 2001
From: Sven Schnelle svens@linux.ibm.com Date: Fri, 25 Jun 2021 15:02:08 +0200 Subject: [PATCH] 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: stable@kernel.org # v5.12+ d57778feb987: s390/vdso: always enable vdso Cc: stable@kernel.org # v5.12+ 686341f2548b: s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall Cc: stable@kernel.org # v5.12+ 43e1f76b0b69: s390/vdso: rename VDSO64_LBASE to VDSO_LBASE Cc: stable@kernel.org # v5.12+ 779df2248739: s390/vdso: add minimal compat vdso Cc: stable@kernel.org # v5.12+ Signed-off-by: Sven Schnelle svens@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com
diff --git a/arch/s390/kernel/compat_signal.c b/arch/s390/kernel/compat_signal.c index 1d0e17ec93eb..cca142fbb516 100644 --- a/arch/s390/kernel/compat_signal.c +++ b/arch/s390/kernel/compat_signal.c @@ -28,6 +28,7 @@ #include <linux/uaccess.h> #include <asm/lowcore.h> #include <asm/switch_to.h> +#include <asm/vdso.h> #include "compat_linux.h" #include "compat_ptrace.h" #include "entry.h" @@ -118,7 +119,6 @@ static int restore_sigregs32(struct pt_regs *regs,_sigregs32 __user *sregs) fpregs_load((_s390_fp_regs *) &user_sregs.fpregs, ¤t->thread.fpu);
clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */ - clear_pt_regs_flag(regs, PIF_SYSCALL_RESTART); return 0; }
@@ -304,11 +304,7 @@ static int setup_frame32(struct ksignal *ksig, sigset_t *set, restorer = (unsigned long __force) ksig->ka.sa.sa_restorer | PSW32_ADDR_AMODE; } else { - /* Signal frames without vectors registers are short ! */ - __u16 __user *svc = (void __user *) frame + frame_size - 2; - if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn, svc)) - return -EFAULT; - restorer = (unsigned long __force) svc | PSW32_ADDR_AMODE; + restorer = VDSO32_SYMBOL(current, sigreturn); }
/* Set up registers for signal handler */ @@ -371,10 +367,7 @@ static int setup_rt_frame32(struct ksignal *ksig, sigset_t *set, restorer = (unsigned long __force) ksig->ka.sa.sa_restorer | PSW32_ADDR_AMODE; } else { - __u16 __user *svc = &frame->svc_insn; - if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn, svc)) - return -EFAULT; - restorer = (unsigned long __force) svc | PSW32_ADDR_AMODE; + restorer = VDSO32_SYMBOL(current, rt_sigreturn); }
/* Create siginfo on the signal stack */ 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; }
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c index 080e7aed181f..78ef53b29958 100644 --- a/arch/s390/kernel/signal.c +++ b/arch/s390/kernel/signal.c @@ -32,6 +32,7 @@ #include <linux/uaccess.h> #include <asm/lowcore.h> #include <asm/switch_to.h> +#include <asm/vdso.h> #include "entry.h"
/* @@ -171,7 +172,6 @@ static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs) fpregs_load(&user_sregs.fpregs, ¤t->thread.fpu);
clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */ - clear_pt_regs_flag(regs, PIF_SYSCALL_RESTART); return 0; }
@@ -334,15 +334,10 @@ static int setup_frame(int sig, struct k_sigaction *ka,
/* Set up to return from userspace. If provided, use a stub already in userspace. */ - if (ka->sa.sa_flags & SA_RESTORER) { + if (ka->sa.sa_flags & SA_RESTORER) restorer = (unsigned long) ka->sa.sa_restorer; - } else { - /* Signal frame without vector registers are short ! */ - __u16 __user *svc = (void __user *) frame + frame_size - 2; - if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn, svc)) - return -EFAULT; - restorer = (unsigned long) svc; - } + else + restorer = VDSO64_SYMBOL(current, sigreturn);
/* Set up registers for signal handler */ regs->gprs[14] = restorer; @@ -397,14 +392,10 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
/* Set up to return from userspace. If provided, use a stub already in userspace. */ - if (ksig->ka.sa.sa_flags & SA_RESTORER) { + if (ksig->ka.sa.sa_flags & SA_RESTORER) restorer = (unsigned long) ksig->ka.sa.sa_restorer; - } else { - __u16 __user *svc = &frame->svc_insn; - if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn, svc)) - return -EFAULT; - restorer = (unsigned long) svc; - } + else + restorer = VDSO64_SYMBOL(current, rt_sigreturn);
/* Create siginfo on the signal stack */ if (copy_siginfo_to_user(&frame->info, &ksig->info)) @@ -501,7 +492,7 @@ void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) } /* No longer in a system call */ clear_pt_regs_flag(regs, PIF_SYSCALL); - clear_pt_regs_flag(regs, PIF_SYSCALL_RESTART); + rseq_signal_deliver(&ksig, regs); if (is_compat_task()) handle_signal32(&ksig, oldset, regs); @@ -517,14 +508,20 @@ void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) switch (regs->gprs[2]) { case -ERESTART_RESTARTBLOCK: /* Restart with sys_restart_syscall */ - regs->int_code = __NR_restart_syscall; - fallthrough; + regs->gprs[2] = regs->orig_gpr2; + current->restart_block.arch_data = regs->psw.addr; + if (is_compat_task()) + regs->psw.addr = VDSO32_SYMBOL(current, restart_syscall); + else + regs->psw.addr = VDSO64_SYMBOL(current, restart_syscall); + if (test_thread_flag(TIF_SINGLE_STEP)) + clear_thread_flag(TIF_PER_TRAP); + break; case -ERESTARTNOHAND: case -ERESTARTSYS: case -ERESTARTNOINTR: - /* Restart system call with magic TIF bit. */ regs->gprs[2] = regs->orig_gpr2; - set_pt_regs_flag(regs, PIF_SYSCALL_RESTART); + regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); if (test_thread_flag(TIF_SINGLE_STEP)) clear_thread_flag(TIF_PER_TRAP); break; diff --git a/arch/s390/kernel/syscall.c b/arch/s390/kernel/syscall.c index 76f7916cc30f..c6b99da0738b 100644 --- a/arch/s390/kernel/syscall.c +++ b/arch/s390/kernel/syscall.c @@ -121,6 +121,10 @@ void do_syscall(struct pt_regs *regs)
regs->gprs[2] = nr;
+ if (nr == __NR_restart_syscall && !(current->restart_block.arch_data & 1)) { + regs->psw.addr = current->restart_block.arch_data; + current->restart_block.arch_data = 1; + } nr = syscall_enter_from_user_mode_work(regs, nr);
/*