linux-kernel - [PATCH 3.16.y-ckt 054/180] KVM: s390: reinjection of irqs can fail in the tpi handler

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Date:	Thu,  7 May 2015 10:44:23 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 054/180] KVM: s390: reinjection of irqs can fail in the tpi handler

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Hildenbrand <dahi@...ux.vnet.ibm.com>

commit 15462e37ca848abac7477dece65f8af25febd744 upstream.

The reinjection of an I/O interrupt can fail if the list is at the limit
and between the dequeue and the reinjection, another I/O interrupt is
injected (e.g. if user space floods kvm with I/O interrupts).

This patch avoids this memory leak and returns -EFAULT in this special
case. This error is not recoverable, so let's fail hard. This can later
be avoided by not dequeuing the interrupt but working directly on the
locked list.

Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/s390/kvm/interrupt.c | 4 ++--
 arch/s390/kvm/kvm-s390.h  | 4 ++--
 arch/s390/kvm/priv.c      | 5 ++++-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index f19702fc89ec..be5fb350d255 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1007,10 +1007,10 @@ int kvm_s390_inject_vm(struct kvm *kvm,
 	return rc;
 }
 
-void kvm_s390_reinject_io_int(struct kvm *kvm,
+int kvm_s390_reinject_io_int(struct kvm *kvm,
 			      struct kvm_s390_interrupt_info *inti)
 {
-	__inject_vm(kvm, inti);
+	return __inject_vm(kvm, inti);
 }
 
 int kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu,
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index a8655ed31616..3d08a076729f 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -143,8 +143,8 @@ int __must_check kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu,
 int __must_check kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code);
 struct kvm_s390_interrupt_info *kvm_s390_get_io_int(struct kvm *kvm,
 						    u64 cr6, u64 schid);
-void kvm_s390_reinject_io_int(struct kvm *kvm,
-			      struct kvm_s390_interrupt_info *inti);
+int kvm_s390_reinject_io_int(struct kvm *kvm,
+			     struct kvm_s390_interrupt_info *inti);
 int kvm_s390_mask_adapter(struct kvm *kvm, unsigned int id, bool masked);
 
 /* implemented in priv.c */
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index a07965490779..8a5156d85c70 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -278,7 +278,10 @@ reinject_interrupt:
 	 * instruction is suppressed from the guest's view: reinject the
 	 * interrupt.
 	 */
-	kvm_s390_reinject_io_int(vcpu->kvm, inti);
+	if (kvm_s390_reinject_io_int(vcpu->kvm, inti)) {
+		kfree(inti);
+		rc = -EFAULT;
+	}
 	/* don't set the cc, a pgm irq was injected or we drop to user space */
 	return rc ? -EFAULT : 0;
 }
--
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