When an MSI descriptor was not available, the error path would try to
unbind an irq that was never acquired - potentially unbinding an
unrelated irq.

Fixes: 4892c9b4ada9f9 ("xen: add support for MSI message groups")
Reported-by: Hooman Mirhadi <[email protected]>
CC: <[email protected]>
CC: Roger Pau Monné <[email protected]>
CC: Boris Ostrovsky <[email protected]>
CC: Eduardo Valentin <[email protected]>
CC: Juergen Gross <[email protected]>
CC: Thomas Gleixner <[email protected]>
CC: "K. Y. Srinivasan" <[email protected]>
CC: Liu Shuo <[email protected]>
CC: Anoob Soman <[email protected]>
Signed-off-by: Amit Shah <[email protected]>
---
 drivers/xen/events/events_base.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 1ab4bd1..c86d10e 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -755,8 +755,10 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct 
msi_desc *msidesc,
        mutex_unlock(&irq_mapping_update_lock);
        return irq;
 error_irq:
-       for (; i >= 0; i--)
+       while (i > 0) {
+               i--;
                __unbind_from_irq(irq + i);
+       }
        mutex_unlock(&irq_mapping_update_lock);
        return ret;
 }
-- 
2.7.3.AMZN

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