[PATCH] kvm-kmod: fix kvm_request_irq race

Chris Wright
2009-05-21T06:21:48Z

Commit "32658734: Fix request_irq() for < 2.6.19" is racy between multiple
guests since ioctl is only serialized per guest. Add mutex and serialize
kvm_request_irq/kvm_free_irq to avoid race.

Signed-off-by: Chris Wright <chrisw@redhat.com>
---
external-module-compat-comm.h | 14 +++++++++++---
1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/external-module-compat-comm.h b/external-module-compat-comm.h
index 8cb5440..eaad986 100644
--- a/external-module-compat-comm.h
+++ b/external-module-compat-comm.h
@@ -645,6 +645,7 @@ static inline int pci_reset_function(struct pci_dev *dev)

typedef irqreturn_t (*kvm_irq_handler_t)(int, void *);
static kvm_irq_handler_t kvm_irq_handlers[NR_IRQS];
+static DEFINE_MUTEX(kvm_irq_handlers_mutex);

static irqreturn_t kvm_irq_thunk(int irq, void *dev_id, struct pt_regs *regs)
{
@@ -655,21 +656,28 @@ static irqreturn_t kvm_irq_thunk(int irq, void *dev_id, struct pt_regs *regs)
static inline int kvm_request_irq(unsigned int a, kvm_irq_handler_t handler,
unsigned long c, const char *d, void *e)
{
- int rc;
- kvm_irq_handler_t old = kvm_irq_handlers[a];
+ int rc = -EBUSY;
+ kvm_irq_handler_t old;
+
+ mutex_lock(&kvm_irq_handlers_mutex);
+ old = kvm_irq_handlers[a];
if (old)
- return -EBUSY;
+ goto out;
kvm_irq_handlers[a] = handler;
rc = request_irq(a, kvm_irq_thunk, c, d, e);
if (rc)
kvm_irq_handlers[a] = NULL;
+out:
+ mutex_unlock(&kvm_irq_handlers_mutex);
return rc;
}

static inline void kvm_free_irq(unsigned int irq, void *dev_id)
{
+ mutex_lock(&kvm_irq_handlers_mutex);
free_irq(irq, dev_id);
kvm_irq_handlers[irq] = NULL;
+ mutex_unlock(&kvm_irq_handlers_mutex);
}

#else