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Patch "KVM: Let KVM_SET_SIGNAL_MASK work as advertised" has been added to the 4.14-stable tree

PATCH [email protected] 1 participant 1 message Feb 1, 2018

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Stable branch x86 KVM PowerPC +6 more subsystems
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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;a=summary

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 <[email protected]> know about it.

Quoted 1 line

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

From: "Jan H. Sch�nherr" <[email protected]>
Date: Fri, 24 Nov 2017 22:39:01 +0100
Subject: KVM: Let KVM_SET_SIGNAL_MASK work as advertised

From: "Jan H. Sch�nherr" <[email protected]>

[ 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 <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 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(-)
arch/mips/kvm/mips.c +2 -5
@@ -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;
 }
arch/powerpc/kvm/powerpc.c +2 -5
@@ -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;
 }
arch/s390/kvm/kvm-s390.c +2 -5
@@ -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;
arch/x86/kvm/x86.c +2 -5
@@ -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;
 }
include/linux/kvm_host.h +3 -0
@@ -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);
virt/kvm/arm/arm.c +3 -5
@@ -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;
 }
virt/kvm/kvm_main.c +23 -0
@@ -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 [email protected] are

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