[PATCH v2] staging: media: ipu7: fix double-free and use-after-free in error paths

[Alexandru Hossu <hossu.alexandru@gmail.com>]

In both ipu7_isys_init() and ipu7_psys_init(), pdata is allocated and
then passed to ipu7_bus_initialize_device(), which stores it in
adev->pdata. The ipu7_bus_release() function frees adev->pdata when the
device's reference count drops to zero.

Two error paths incorrectly call kfree(pdata) after the device teardown
has already freed it:

1. When ipu7_mmu_init() fails: put_device() is called, which drops the
   reference count to zero and triggers ipu7_bus_release() ->
   kfree(pdata). The subsequent kfree(pdata) is a double-free.

2. When ipu7_bus_add_device() fails: it calls auxiliary_device_uninit()
   internally, which calls put_device() -> ipu7_bus_release() ->
   kfree(pdata). The subsequent kfree(pdata) is again a double-free.

Note that the kfree(pdata) when ipu7_bus_initialize_device() itself
fails is correct, because in that case auxiliary_device_init() failed
and the release function was never set up, so pdata must be freed
manually.

Additionally, the error code was not saved before calling put_device(),
causing ERR_CAST() to dereference the already-freed adev pointer when
constructing the return value. Fix this by saving the error from
dev_err_probe() before put_device() and returning ERR_PTR() instead.

Remove the redundant kfree(pdata) calls and fix the use-after-free in
the return values of the two affected error paths.

Fixes: b7fe4c0019b1 ("media: staging/ipu7: add Intel IPU7 PCI device driver")
Signed-off-by: Alexandru Hossu <hossu.alexandru@gmail.com>
---
v2:
 - Add Fixes tag (Dan Carpenter)
 - Save error before put_device() to avoid use-after-free in ERR_CAST()
   return value; use ERR_PTR(ret) instead (Dan Carpenter)
 - Apply same fix to ipu7_psys_init() (Dan Carpenter)

 drivers/staging/media/ipu7/ipu7.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/media/ipu7/ipu7.c b/drivers/staging/media/ipu7/ipu7.c
index c771e763f8c5..310e3f24e571 100644
--- a/drivers/staging/media/ipu7/ipu7.c
+++ b/drivers/staging/media/ipu7/ipu7.c
@@ -2169,21 +2169,18 @@ ipu7_isys_init(struct pci_dev *pdev, struct device *parent,
 	isys_adev->mmu = ipu7_mmu_init(dev, base, ISYS_MMID,
 				       &ipdata->hw_variant);
 	if (IS_ERR(isys_adev->mmu)) {
-		dev_err_probe(dev, PTR_ERR(isys_adev->mmu),
-			      "ipu7_mmu_init(isys_adev->mmu) failed\n");
+		ret = dev_err_probe(dev, PTR_ERR(isys_adev->mmu),
+				    "ipu7_mmu_init(isys_adev->mmu) failed\n");
 		put_device(&isys_adev->auxdev.dev);
-		kfree(pdata);
-		return ERR_CAST(isys_adev->mmu);
+		return ERR_PTR(ret);
 	}
 
 	isys_adev->mmu->dev = &isys_adev->auxdev.dev;
 	isys_adev->subsys = IPU_IS;
 
 	ret = ipu7_bus_add_device(isys_adev);
-	if (ret) {
-		kfree(pdata);
+	if (ret)
 		return ERR_PTR(ret);
-	}
 
 	return isys_adev;
 }
@@ -2216,21 +2213,18 @@ ipu7_psys_init(struct pci_dev *pdev, struct device *parent,
 	psys_adev->mmu = ipu7_mmu_init(&pdev->dev, base, PSYS_MMID,
 				       &ipdata->hw_variant);
 	if (IS_ERR(psys_adev->mmu)) {
-		dev_err_probe(&pdev->dev, PTR_ERR(psys_adev->mmu),
-			      "ipu7_mmu_init(psys_adev->mmu) failed\n");
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(psys_adev->mmu),
+				    "ipu7_mmu_init(psys_adev->mmu) failed\n");
 		put_device(&psys_adev->auxdev.dev);
-		kfree(pdata);
-		return ERR_CAST(psys_adev->mmu);
+		return ERR_PTR(ret);
 	}
 
 	psys_adev->mmu->dev = &psys_adev->auxdev.dev;
 	psys_adev->subsys = IPU_PS;
 
 	ret = ipu7_bus_add_device(psys_adev);
-	if (ret) {
-		kfree(pdata);
+	if (ret)
 		return ERR_PTR(ret);
-	}
 
 	return psys_adev;
 }
-- 
2.53.0