[PATCH v4] uio: uio_pci_generic_sva: fix double free of devm_kzalloc() memory

[Guangshuo Li]

uio_pci_sva allocates struct uio_pci_sva_dev with devm_kzalloc() in
probe(), but then calls kfree(udev) both on the probe() error path
(label out_free) and again in remove().

Because devm_kzalloc() allocations are devres-managed and are freed
automatically when the device is detached (including after a failing
probe() and during driver unbind), the explicit kfree() can lead to a
double free.

If probe() fails after devm_kzalloc(), the error path frees udev and
devres cleanup will free it again when the core unwinds the partially
bound device. On normal driver removal, remove() frees udev and devres
will free it again when the device is detached.

This issue was identified by a static analysis tool I developed and
confirmed by manual review. Fix by removing the manual kfree() calls
and dropping the now-unused label.

Fixes: 3397c3cd859a2 ("uio: Add SVA support for PCI devices via uio_pci_generic_sva.c")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
---
v4:
  - Add description of how the issue was found and tested.

v3:
  - Add changelog below the --- line describing changes since v2.

v2:
  - Reflow commit message to keep lines within 75 characters.

 drivers/uio/uio_pci_generic_sva.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/uio/uio_pci_generic_sva.c b/drivers/uio/uio_pci_generic_sva.c
index 4a46acd994a8..152201047334 100644
--- a/drivers/uio/uio_pci_generic_sva.c
+++ b/drivers/uio/uio_pci_generic_sva.c
@@ -129,15 +129,13 @@ static int probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	ret = devm_uio_register_device(&pdev->dev, &udev->info);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register uio device\n");
-		goto out_free;
+		goto out_disable;
 	}
 
 	pci_set_drvdata(pdev, udev);
 
 	return 0;
 
-out_free:
-	kfree(udev);
 out_disable:
 	pci_disable_device(pdev);
 
@@ -150,7 +148,6 @@ static void remove(struct pci_dev *pdev)
 
 	pci_release_regions(pdev);
 	pci_disable_device(pdev);
-	kfree(udev);
 }
 
 static ssize_t pasid_show(struct device *dev,
-- 
2.43.0