Patch "vfio/pci: Disable auto-enable of exclusive INTx IRQ" has been added to the 6.7-stable tree

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This is a note to let you know that I've just added the patch titled

    vfio/pci: Disable auto-enable of exclusive INTx IRQ

to the 6.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vfio-pci-disable-auto-enable-of-exclusive-intx-irq.patch
and it can be found in the queue-6.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c55d06b9673ed688ed33606104a620c5022f1d26
Author: Alex Williamson <alex.williamson@xxxxxxxxxx>
Date:   Fri Mar 8 16:05:22 2024 -0700

    vfio/pci: Disable auto-enable of exclusive INTx IRQ
    
    [ Upstream commit fe9a7082684eb059b925c535682e68c34d487d43 ]
    
    Currently for devices requiring masking at the irqchip for INTx, ie.
    devices without DisINTx support, the IRQ is enabled in request_irq()
    and subsequently disabled as necessary to align with the masked status
    flag.  This presents a window where the interrupt could fire between
    these events, resulting in the IRQ incrementing the disable depth twice.
    This would be unrecoverable for a user since the masked flag prevents
    nested enables through vfio.
    
    Instead, invert the logic using IRQF_NO_AUTOEN such that exclusive INTx
    is never auto-enabled, then unmask as required.
    
    Cc:  <stable@xxxxxxxxxxxxxxx>
    Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240308230557.805580-2-alex.williamson@xxxxxxxxxx
    Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index cbb4bcbfbf83d..3dbeeb5bfadce 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -296,8 +296,15 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
 
 	ctx->trigger = trigger;
 
+	/*
+	 * Devices without DisINTx support require an exclusive interrupt,
+	 * IRQ masking is performed at the IRQ chip.  The masked status is
+	 * protected by vdev->irqlock. Setup the IRQ without auto-enable and
+	 * unmask as necessary below under lock.  DisINTx is unmodified by
+	 * the IRQ configuration and may therefore use auto-enable.
+	 */
 	if (!vdev->pci_2_3)
-		irqflags = 0;
+		irqflags = IRQF_NO_AUTOEN;
 
 	ret = request_irq(pdev->irq, vfio_intx_handler,
 			  irqflags, ctx->name, vdev);
@@ -308,13 +315,9 @@ static int vfio_intx_set_signal(struct vfio_pci_core_device *vdev, int fd)
 		return ret;
 	}
 
-	/*
-	 * INTx disable will stick across the new irq setup,
-	 * disable_irq won't.
-	 */
 	spin_lock_irqsave(&vdev->irqlock, flags);
-	if (!vdev->pci_2_3 && ctx->masked)
-		disable_irq_nosync(pdev->irq);
+	if (!vdev->pci_2_3 && !ctx->masked)
+		enable_irq(pdev->irq);
 	spin_unlock_irqrestore(&vdev->irqlock, flags);
 
 	return 0;




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