KVM: Let KVM_SET_SIGNAL_MASK work as advertised

[ 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>

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index d535edc01434117a8809fc21fb152226e0b46521..75fdeaa8c62f21a5420c963968c0188bbb459f49 100644 (file)
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -445,10 +445,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 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_vcpu *vcpu, struct kvm_run *run)
        local_irq_enable();
 
 out:
-       if (vcpu->sigset_active)
-               sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+       kvm_sigset_deactivate(vcpu);
 
        return r;
 }

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index ee279c7f48021e0b43c658d7529b9160061b5415..2b02d51d14d89bc896b23f0b886c05cb0b0a4c40 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -1407,7 +1407,6 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 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_vcpu *vcpu, struct kvm_run *run)
 #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;
 }

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6c88cb18ace2e302b7a59335ec0a9d00ac473355..6e3d80b2048e5da2abd33e2d5498f3c2599e1ea6 100644 (file)
--- 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 *vcpu, struct kvm_run *kvm_run)
 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_vcpu *vcpu, struct kvm_run *kvm_run)
                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_vcpu *vcpu, struct kvm_run *kvm_run)
        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;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2dd19f2342457f90aceab1dd3381ff69228b4a7d..8c28023a43b13227e622d17f0164f85c1c0e8489 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7245,12 +7245,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
        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_vcpu *vcpu, struct kvm_run *kvm_run)
 
 out:
        post_kvm_run_save(vcpu);
-       if (vcpu->sigset_active)
-               sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+       kvm_sigset_deactivate(vcpu);
 
        return r;
 }

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6882538eda329fb4a59c4bb1b2957003f6fdb9e9..5a8019befafdcbe1a2ff23b3b99c270e10cdb884 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -714,6 +714,9 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
                         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);

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 95cba079982897bb5b1a1ab6a5717aa080d021b4..9a07ee94a2306b1e73231e1877071ca3d600d720 100644 (file)
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -612,7 +612,6 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 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_vcpu *vcpu, struct kvm_run *run)
        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_vcpu *vcpu, struct kvm_run *run)
                kvm_pmu_update_run(vcpu);
        }
 
-       if (vcpu->sigset_active)
-               sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+       kvm_sigset_deactivate(vcpu);
+
        return ret;
 }
 

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2447d7c017e7079645dff262e2d0466327e59d63..8401774f5aeb8cea73d3ead1c7870484a25858a9 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2073,6 +2073,29 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn)
 }
 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;