[PATCH v4 3/5] ata: libahci: Free the IRQs when activating a multi-IRQ host fails

[Niklas Cassel <cassel@kernel.org>]

ahci_host_activate_multi_irqs() requests one IRQ per port, but it does
not free them when requesting one of them, or when registering the host,
fails. The IRQs are only freed by the driver core, when it releases the
devres of the device after probe() has returned, while the caller of
ahci_host_activate() releases the resources of the host in its probe()
error path, e.g. ahci_probe() disables the clocks, regulators, resets and
PHYs of the host. An IRQ handler running in that window would access the
MMIO of a host which is no longer clocked.

ahci_host_activate_multi_irqs() did free the IRQs until commit
0a142b26921c ("ahci: cleanup ahci_host_activate_multi_irqs"), which
removed the explicit free because devm makes it unnecessary. That is true
for freeing the IRQs as such, but not for the window described above:
devres is only released after probe() has returned, i.e. after the error
path of the caller has released the resources of the host.

Note that this window cannot be hit with the current users: the only user
of AHCI_HFLAG_MULTI_MSI is the AHCI PCI driver, which does not release
any resource in its probe() error path, and the ports of the host are
still frozen, i.e. their interrupts are masked, when ata_host_register()
fails.

Free the IRQs explicitly again, like ata_host_activate() does, so that
the IRQ handlers cannot run once ahci_host_activate() has failed.

Fixes: 0a142b26921c ("ahci: cleanup ahci_host_activate_multi_irqs")
Cc: stable@vger.kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/ata/libahci.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 6d72eb017b49..9f479daa89b0 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -2723,11 +2723,33 @@ static int ahci_host_activate_multi_irqs(struct ata_host *host,
 				0, pp->irq_desc, host->ports[i]);
 
 		if (rc)
-			return rc;
+			goto free_irqs;
 		ata_port_desc_misc(host->ports[i], irq);
 	}
 
-	return ata_host_register(host, sht);
+	rc = ata_host_register(host, sht);
+	if (rc)
+		goto free_irqs;
+
+	return 0;
+
+free_irqs:
+	/*
+	 * Free the IRQs which have been requested, so that the handlers can no
+	 * longer access the MMIO of the host once we return, e.g. after the
+	 * caller has disabled the clocks of the host.
+	 */
+	while (--i >= 0) {
+		struct ahci_port_priv *pp = host->ports[i]->private_data;
+
+		if (!pp)
+			continue;
+
+		devm_free_irq(host->dev, hpriv->get_irq_vector(host, i),
+			      host->ports[i]);
+	}
+
+	return rc;
 }
 
 /**
-- 
2.55.0