This is a note to let you know that I've just added the patch titled

KVM: Let KVM_SET_SIGNAL_MASK work as advertised

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kvm-let-kvm_set_signal_mask-work-as-advertised.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Feb 1 13:45:42 CET 2018

From: "Jan H. Schönherr" jschoenh@amazon.de Date: Fri, 24 Nov 2017 22:39:01 +0100 Subject: KVM: Let KVM_SET_SIGNAL_MASK work as advertised

From: "Jan H. Schönherr" jschoenh@amazon.de

[ Upstream commit 20b7035c66bacc909ae3ffe92c1a1ea7db99fe4f ]

KVM API says for the signal mask you set via KVM_SET_SIGNAL_MASK, that "any unblocked signal received [...] will cause KVM_RUN to return with -EINTR" and that "the signal will only be delivered if not blocked by the original signal mask".

This, however, is only true, when the calling task has a signal handler registered for a signal. If not, signal evaluation is short-circuited for SIG_IGN and SIG_DFL, and the signal is either ignored without KVM_RUN returning or the whole process is terminated.

Make KVM_SET_SIGNAL_MASK behave as advertised by utilizing logic similar to that in do_sigtimedwait() to avoid short-circuiting of signals.

Signed-off-by: Jan H. Schönherr jschoenh@amazon.de Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/mips/kvm/mips.c | 7 ++----- arch/powerpc/kvm/powerpc.c | 7 ++----- arch/s390/kvm/kvm-s390.c | 7 ++----- arch/x86/kvm/x86.c | 7 ++----- include/linux/kvm_host.h | 3 +++ virt/kvm/arm/arm.c | 8 +++----- virt/kvm/kvm_main.c | 23 +++++++++++++++++++++++ 7 files changed, 37 insertions(+), 25 deletions(-)

--- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -445,10 +445,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug( int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) { int r = -EINTR; - sigset_t sigsaved;

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); + kvm_sigset_activate(vcpu);

if (vcpu->mmio_needed) { if (!vcpu->mmio_is_write) @@ -480,8 +478,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v local_irq_enable();

out: - if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &sigsaved, NULL); + kvm_sigset_deactivate(vcpu);

return r; } --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -1407,7 +1407,6 @@ int kvm_vcpu_ioctl_set_one_reg(struct kv int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) { int r; - sigset_t sigsaved;

if (vcpu->mmio_needed) { vcpu->mmio_needed = 0; @@ -1448,16 +1447,14 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v #endif }

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); + kvm_sigset_activate(vcpu);

if (run->immediate_exit) r = -EINTR; else r = kvmppc_vcpu_run(run, vcpu);

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &sigsaved, NULL); + kvm_sigset_deactivate(vcpu);

return r; } --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -3378,7 +3378,6 @@ static void store_regs(struct kvm_vcpu * int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) { int rc; - sigset_t sigsaved;

if (kvm_run->immediate_exit) return -EINTR; @@ -3388,8 +3387,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v return 0; }

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); + kvm_sigset_activate(vcpu);

if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm)) { kvm_s390_vcpu_start(vcpu); @@ -3423,8 +3421,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v disable_cpu_timer_accounting(vcpu); store_regs(vcpu, kvm_run);

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &sigsaved, NULL); + kvm_sigset_deactivate(vcpu);

vcpu->stat.exit_userspace++; return rc; --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7245,12 +7245,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v { struct fpu *fpu = &current->thread.fpu; int r; - sigset_t sigsaved;

fpu__initialize(fpu);

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); + kvm_sigset_activate(vcpu);

if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) { if (kvm_run->immediate_exit) { @@ -7293,8 +7291,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v

out: post_kvm_run_save(vcpu); - if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &sigsaved, NULL); + kvm_sigset_deactivate(vcpu);

return r; } --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -714,6 +714,9 @@ int kvm_vcpu_write_guest(struct kvm_vcpu unsigned long len); void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);

+void kvm_sigset_activate(struct kvm_vcpu *vcpu); +void kvm_sigset_deactivate(struct kvm_vcpu *vcpu); + void kvm_vcpu_block(struct kvm_vcpu *vcpu); void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu); void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu); --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -612,7 +612,6 @@ static void check_vcpu_requests(struct k int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) { int ret; - sigset_t sigsaved;

if (unlikely(!kvm_vcpu_initialized(vcpu))) return -ENOEXEC; @@ -630,8 +629,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v if (run->immediate_exit) return -EINTR;

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); + kvm_sigset_activate(vcpu);

ret = 1; run->exit_reason = KVM_EXIT_UNKNOWN; @@ -753,8 +751,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_v kvm_pmu_update_run(vcpu); }

- if (vcpu->sigset_active) - sigprocmask(SIG_SETMASK, &sigsaved, NULL); + kvm_sigset_deactivate(vcpu); + return ret; }

--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2073,6 +2073,29 @@ void kvm_vcpu_mark_page_dirty(struct kvm } EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);

+void kvm_sigset_activate(struct kvm_vcpu *vcpu) +{ + if (!vcpu->sigset_active) + return; + + /* + * This does a lockless modification of ->real_blocked, which is fine + * because, only current can change ->real_blocked and all readers of + * ->real_blocked don't care as long ->real_blocked is always a subset + * of ->blocked. + */ + sigprocmask(SIG_SETMASK, &vcpu->sigset, &current->real_blocked); +} + +void kvm_sigset_deactivate(struct kvm_vcpu *vcpu) +{ + if (!vcpu->sigset_active) + return; + + sigprocmask(SIG_SETMASK, &current->real_blocked, NULL); + sigemptyset(&current->real_blocked); +} + static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) { unsigned int old, val, grow;

Patches currently in stable-queue which might be from jschoenh@amazon.de are

queue-4.14/kvm-let-kvm_set_signal_mask-work-as-advertised.patch