[PATCH] genirq/msi: Take the per-device MSI lock before validating the control structure

[Marc Zyngier]

Calling msi_ctrl_valid() ultimately results in calling
msi_get_device_domain(), which requires holding the device MSI lock.

However, we take that lock right after having called msi_ctrl_valid(),
which is just a tad too late. Taking the lock earlier solves the issue.

Fixes: 40742716f294 ("genirq/msi: Make msi_add_simple_msi_descs() device domain aware")
Reported-by: "Russell King (Oracle)" <linux@xxxxxxxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/Y/Opu6ETe3ZzZ/8E@xxxxxxxxxxxxxxxxxxxxx
---
 kernel/irq/msi.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 783a3e6a0b10..13d96495e6d0 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -1084,10 +1084,13 @@ int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
 	struct xarray *xa;
 	int ret, virq;
 
-	if (!msi_ctrl_valid(dev, &ctrl))
-		return -EINVAL;
-
 	msi_lock_descs(dev);
+
+	if (!msi_ctrl_valid(dev, &ctrl)) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
 	ret = msi_domain_add_simple_msi_descs(dev, &ctrl);
 	if (ret)
 		goto unlock;
-- 
2.34.1