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KVM: s390: fix get_all_floating_irqs

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This fixes a bug introduced with commit c05c4186bb ("KVM: s390:
add floating irq controller").

get_all_floating_irqs() does copy_to_user() while holding
a spin lock. Let's fix this by filling a temporary buffer
first and copy it to userspace after giving up the lock.

Cc: <stable@vger.kernel.org> # 3.18+: 69a8d45626 KVM: s390: no need to hold...

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This commit is contained in:
Jens Freimann 2015-03-16 12:17:13 +01:00 committed by Christian Borntraeger
parent a3ed8dae6e
commit 94aa033efc
2 changed files with 35 additions and 26 deletions
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3
Documentation/virtual/kvm/devices/s390_flic.txt
View file

@ -27,6 +27,9 @@ Groups:
Copies all floating interrupts into a buffer provided by userspace.
When the buffer is too small it returns -ENOMEM, which is the indication
for userspace to try again with a bigger buffer.
-ENOBUFS is returned when the allocation of a kernelspace buffer has
failed.
-EFAULT is returned when copying data to userspace failed.
All interrupts remain pending, i.e. are not deleted from the list of
currently pending interrupts.
attr->addr contains the userspace address of the buffer into which all

58
arch/s390/kvm/interrupt.c
View file

@ -17,6 +17,7 @@
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/bitmap.h>
#include <linux/vmalloc.h>
#include <asm/asm-offsets.h>
#include <asm/dis.h>
#include <asm/uaccess.h>
@ -1477,61 +1478,66 @@ void kvm_s390_clear_float_irqs(struct kvm *kvm)
spin_unlock(&fi->lock);
}
static inline int copy_irq_to_user(struct kvm_s390_interrupt_info *inti,
u8 *addr)
static void inti_to_irq(struct kvm_s390_interrupt_info *inti,
struct kvm_s390_irq *irq)
{
struct kvm_s390_irq __user *uptr = (struct kvm_s390_irq __user *) addr;
struct kvm_s390_irq irq = {0};
irq.type = inti->type;
irq->type = inti->type;
switch (inti->type) {
case KVM_S390_INT_PFAULT_INIT:
case KVM_S390_INT_PFAULT_DONE:
case KVM_S390_INT_VIRTIO:
case KVM_S390_INT_SERVICE:
irq.u.ext = inti->ext;
irq->u.ext = inti->ext;
break;
case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX:
irq.u.io = inti->io;
irq->u.io = inti->io;
break;
case KVM_S390_MCHK:
irq.u.mchk = inti->mchk;
irq->u.mchk = inti->mchk;
break;
default:
return -EINVAL;
}
if (copy_to_user(uptr, &irq, sizeof(irq)))
return -EFAULT;
return 0;
}
static int get_all_floating_irqs(struct kvm *kvm, __u8 *buf, __u64 len)
static int get_all_floating_irqs(struct kvm *kvm, u8 __user *usrbuf, u64 len)
{
struct kvm_s390_interrupt_info *inti;
struct kvm_s390_float_interrupt *fi;
struct kvm_s390_irq *buf;
int max_irqs;
int ret = 0;
int n = 0;
if (len > KVM_S390_FLIC_MAX_BUFFER || len == 0)
return -EINVAL;
/*
* We are already using -ENOMEM to signal
* userspace it may retry with a bigger buffer,
* so we need to use something else for this case
*/
buf = vzalloc(len);
if (!buf)
return -ENOBUFS;
max_irqs = len / sizeof(struct kvm_s390_irq);
fi = &kvm->arch.float_int;
spin_lock(&fi->lock);
list_for_each_entry(inti, &fi->list, list) {
if (len < sizeof(struct kvm_s390_irq)) {
if (n == max_irqs) {
/* signal userspace to try again */
ret = -ENOMEM;
break;
}
ret = copy_irq_to_user(inti, buf);
if (ret)
break;
buf += sizeof(struct kvm_s390_irq);
len -= sizeof(struct kvm_s390_irq);
inti_to_irq(inti, &buf[n]);
n++;
}
spin_unlock(&fi->lock);
if (!ret && n > 0) {
if (copy_to_user(usrbuf, buf, sizeof(struct kvm_s390_irq) * n))
ret = -EFAULT;
}
vfree(buf);
return ret < 0 ? ret : n;
}
@ -1542,7 +1548,7 @@ static int flic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
switch (attr->group) {
case KVM_DEV_FLIC_GET_ALL_IRQS:
r = get_all_floating_irqs(dev->kvm, (u8 *) attr->addr,
r = get_all_floating_irqs(dev->kvm, (u8 __user *) attr->addr,
attr->attr);
break;
default: