[PATCH v4 0/5] ata: Do not release the host resources twice on probe() failure

[PATCH v4 0/5] ata: Do not release the host resources twice on probe() failure

[Niklas Cassel]

ata_host_start() registers ata_host_stop() as a devres action as soon as
it has succeeded:

	if (have_stop) {
		start_dr = devres_alloc(ata_host_stop, 0, GFP_KERNEL);
	...
	if (start_dr)
		devres_add(host->dev, start_dr);
	host->flags |= ATA_HOST_STARTED;

From that point on, releasing the host resources is owned by devres: when
probe() fails, the driver core calls devres_release_all(), which calls
ata_host_stop(), which calls ->port_stop() and ->host_stop().

ata_host_activate() and ahci_host_activate_multi_irqs() can however fail
after ata_host_start() has succeeded - devm_kasprintf(),
devm_request_irq() (a shared IRQ conflict) and ata_host_register()
(scsi_add_host(), ata_tport_add()) can all fail - and they return the
error with the devres action still registered. Since the caller cannot
tell whether ata_host_start() succeeded, and since it has to release the
resources for the failures happening before that, all the ahci-platform
drivers release the host resources in their probe() error path, e.g.
ahci_probe() calls ahci_platform_disable_resources() while
ahci_host_stop() does the same through devres.

The clocks, regulators, resets and PHYs of the host are therefore
released twice, which gives refcount underflow warnings from the clk,
regulator and phy cores and, for shared resources, can disable resources
which are still in use by other devices.

Patch 4 adds ata_host_undo_start(), which stops the ports and drops the
devres action without calling ->host_stop(), and calls it from both
activation helpers when they fail, so that "on failure, the caller
releases what it acquired" holds for all of them. sata_qstor and sata_fsl
are the only drivers which implement ->host_stop() while having no error
handling at all for the activate host call, so they get some.

Patches 1 to 3 have to come first, as they fix error paths which patch 4
would otherwise turn into resource leaks, and which are worth fixing on
their own:

- ahci_st is the only ahci-platform driver whose ->host_stop() does more
  than its probe() error path, as it also asserts the "pwr-dwn" reset
  (patch 1).
- sata_fsl releases hcr_base and host_priv in its probe() error path
  although sata_fsl_host_stop() does that as well, which is a
  use-after-free that the two device_create_file() calls after
  ata_host_activate() can trigger today (patch 2).
- ahci_host_activate_multi_irqs() never frees the IRQs which it
  requested when it fails, so the IRQ handlers stay registered while the
  caller releases the resources of the host (patch 3).

Patch 5 is an unrelated kdoc fix that I noticed while documenting the
above.

Changes since v3:
- New patch 2, which fixes the use-after-free of host_priv in the
  probe() error path of sata_fsl. Patch 4 would otherwise make sata_fsl
  leak hcr_base and host_priv when activating the host fails.
- New patch 3, which frees the IRQs requested by
  ahci_host_activate_multi_irqs() when it fails, like
  ata_host_activate() already does.
- Reword the "if failed, just free the IRQ and leave ports alone"
  comment in ata_host_activate(), as the ports are no longer left alone.

Niklas Cassel (5):
  ata: ahci_st: Assert the power down reset in the probe() error path
  ata: sata_fsl: Fix use-after-free of host_priv on probe() failure
  ata: libahci: Free the IRQs when activating a multi-IRQ host fails
  ata: libata: Do not leave ata_host_stop() registered when activation
    fails
  ata: libata-core: Fix the ata_host_register() kdoc

 drivers/ata/ahci_st.c          | 51 ++++++++++++---------
 drivers/ata/libahci.c          | 28 +++++++++++-
 drivers/ata/libahci_platform.c |  4 ++
 drivers/ata/libata-core.c      | 81 ++++++++++++++++++++++++++++++----
 drivers/ata/libata-sff.c       |  5 +++
 drivers/ata/sata_fsl.c         | 24 +++++++---
 drivers/ata/sata_qstor.c       |  8 +++-
 include/linux/libata.h         |  1 +
 8 files changed, 161 insertions(+), 41 deletions(-)

-- 
2.55.0

[PATCH v4 1/5] ata: ahci_st: Assert the power down reset in the probe() error path

[Niklas Cassel]

st_ahci_probe_resets() deasserts the "pwr-dwn" reset, but the probe()
error path of st_ahci_probe() only releases the host resources, so the
SATA IP is left powered up when probe() fails after
st_ahci_probe_resets() has succeeded, e.g. when
ahci_platform_enable_resources() fails.

The reset is asserted by st_ahci_host_stop(), however ->host_stop() is
only called through the ata_host_stop() devres action registered by
ata_host_start(), so it does not cover any failure happening before the
host has been started.

Factor the assert out into st_ahci_assert_pwrdwn() and call it from both
probe() error paths. The "pwr-dwn" reset control is an exclusive one, so
asserting it once more from st_ahci_host_stop() is harmless.

No functional change intended for ->host_stop() and st_ahci_suspend().

Fixes: 76884cb2f7da ("ahci: st: Add support for ST's SATA IP")
Cc: stable@vger.kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/ata/ahci_st.c | 51 +++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 21 deletions(-)

diff --git a/drivers/ata/ahci_st.c b/drivers/ata/ahci_st.c
index 4336c8a6e208..39ebedf93344 100644
--- a/drivers/ata/ahci_st.c
+++ b/drivers/ata/ahci_st.c
@@ -83,18 +83,27 @@ static int st_ahci_deassert_resets(struct ahci_host_priv *hpriv,
 	return 0;
 }
 
-static void st_ahci_host_stop(struct ata_host *host)
+static int st_ahci_assert_pwrdwn(struct ahci_host_priv *hpriv,
+				 struct device *dev)
 {
-	struct ahci_host_priv *hpriv = host->private_data;
 	struct st_ahci_drv_data *drv_data = hpriv->plat_data;
-	struct device *dev = host->dev;
 	int err;
 
-	if (drv_data->pwr) {
-		err = reset_control_assert(drv_data->pwr);
-		if (err)
-			dev_err(dev, "unable to pwrdwn\n");
-	}
+	if (!drv_data->pwr)
+		return 0;
+
+	err = reset_control_assert(drv_data->pwr);
+	if (err)
+		dev_err(dev, "unable to pwrdwn\n");
+
+	return err;
+}
+
+static void st_ahci_host_stop(struct ata_host *host)
+{
+	struct ahci_host_priv *hpriv = host->private_data;
+
+	st_ahci_assert_pwrdwn(hpriv, host->dev);
 
 	ahci_platform_disable_resources(hpriv);
 }
@@ -162,38 +171,38 @@ static int st_ahci_probe(struct platform_device *pdev)
 
 	err = ahci_platform_enable_resources(hpriv);
 	if (err)
-		return err;
+		goto assert_pwrdwn;
 
 	st_ahci_configure_oob(hpriv->mmio);
 
 	err = ahci_platform_init_host(pdev, hpriv, &st_ahci_port_info,
 				      &ahci_platform_sht);
-	if (err) {
-		ahci_platform_disable_resources(hpriv);
-		return err;
-	}
+	if (err)
+		goto disable_resources;
 
 	return 0;
+
+disable_resources:
+	ahci_platform_disable_resources(hpriv);
+assert_pwrdwn:
+	st_ahci_assert_pwrdwn(hpriv, &pdev->dev);
+
+	return err;
 }
 
 static int st_ahci_suspend(struct device *dev)
 {
 	struct ata_host *host = dev_get_drvdata(dev);
 	struct ahci_host_priv *hpriv = host->private_data;
-	struct st_ahci_drv_data *drv_data = hpriv->plat_data;
 	int err;
 
 	err = ahci_platform_suspend_host(dev);
 	if (err)
 		return err;
 
-	if (drv_data->pwr) {
-		err = reset_control_assert(drv_data->pwr);
-		if (err) {
-			dev_err(dev, "unable to pwrdwn");
-			return err;
-		}
-	}
+	err = st_ahci_assert_pwrdwn(hpriv, dev);
+	if (err)
+		return err;
 
 	ahci_platform_disable_resources(hpriv);
 
-- 
2.55.0