[PATCH] net: mana: fix use-after-free in add_adev() error path

[Guangshuo Li <lgs201920130244@gmail.com>]

If auxiliary_device_add() fails, add_adev() calls
auxiliary_device_uninit(adev), whose release callback adev_release()
frees the containing struct mana_adev.

The current error path then falls through to init_fail and accesses
adev->id. Since adev is embedded in struct mana_adev, this may lead
to a use-after-free.

Fix it by storing the allocated auxiliary device id in a local
variable and using that saved id in the cleanup path after
auxiliary_device_uninit().

Fixes: a69839d4327d ("net: mana: Add support for auxiliary device")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 1ad154f9db1a..70d71594c599 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -3362,6 +3362,7 @@ static int add_adev(struct gdma_dev *gd, const char *name)
 {
 	struct auxiliary_device *adev;
 	struct mana_adev *madev;
+	int id;
 	int ret;
 
 	madev = kzalloc(sizeof(*madev), GFP_KERNEL);
@@ -3372,7 +3373,8 @@ static int add_adev(struct gdma_dev *gd, const char *name)
 	ret = mana_adev_idx_alloc();
 	if (ret < 0)
 		goto idx_fail;
-	adev->id = ret;
+	id = ret;
+	adev->id = id;
 
 	adev->name = name;
 	adev->dev.parent = gd->gdma_context->dev;
@@ -3398,7 +3400,7 @@ static int add_adev(struct gdma_dev *gd, const char *name)
 	auxiliary_device_uninit(adev);
 
 init_fail:
-	mana_adev_idx_free(adev->id);
+	mana_adev_idx_free(id);
 
 idx_fail:
 	kfree(madev);
-- 
2.43.0