This is a note to let you know that I've just added the patch titled s390/signal: switch to using vdso for sigreturn and syscall restart to the 5.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: s390-signal-switch-to-using-vdso-for-sigreturn-and-syscall-restart.patch and it can be found in the queue-5.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From df29a7440c4b5c65765c8f60396b3b13063e24e9 Mon Sep 17 00:00:00 2001 From: Sven Schnelle <svens@xxxxxxxxxxxxx> Date: Fri, 25 Jun 2021 15:02:08 +0200 Subject: s390/signal: switch to using vdso for sigreturn and syscall restart From: Sven Schnelle <svens@xxxxxxxxxxxxx> commit df29a7440c4b5c65765c8f60396b3b13063e24e9 upstream. 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@xxxxxxxxxx> # v5.12+ d57778feb987: s390/vdso: always enable vdso Cc: <stable@xxxxxxxxxx> # v5.12+ 686341f2548b: s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall Cc: <stable@xxxxxxxxxx> # v5.12+ 43e1f76b0b69: s390/vdso: rename VDSO64_LBASE to VDSO_LBASE Cc: <stable@xxxxxxxxxx> # v5.12+ 779df2248739: s390/vdso: add minimal compat vdso Cc: <stable@xxxxxxxxxx> # v5.12+ Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxx> Reviewed-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/s390/kernel/compat_signal.c | 13 +++---------- arch/s390/kernel/process.c | 6 ++++++ arch/s390/kernel/signal.c | 39 ++++++++++++++++++--------------------- arch/s390/kernel/syscall.c | 4 ++++ 4 files changed, 31 insertions(+), 31 deletions(-) --- 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_r 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 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 ksign 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 */ --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -166,6 +166,12 @@ int copy_thread(unsigned long clone_flag 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; } --- 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_reg 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 /* 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 /* 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 } /* 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 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; --- 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); /* Patches currently in stable-queue which might be from svens@xxxxxxxxxxxxx are queue-5.12/s390-vdso-rename-vdso64_lbase-to-vdso_lbase.patch queue-5.12/s390-vdso64-add-sigreturn-rt_sigreturn-and-restart_syscall.patch queue-5.12/s390-signal-switch-to-using-vdso-for-sigreturn-and-syscall-restart.patch queue-5.12/s390-vdso-add-minimal-compat-vdso.patch queue-5.12/s390-vdso-always-enable-vdso.patch