[PATCH v3 3/6] drm/amdgpu/aca: Fix inverted validation logic and list cleanup

[Sreeraj S Kurup <sreekuttan2156239@gmail.com>]

aca_handle_is_valid() returned false if !list_empty(&handle->node)
evaluated to true. Because active registered handles have non-empty
nodes in the handle list, valid handles evaluated as invalid.
Consequently, amdgpu_aca_get_error_data() returned -EOPNOTSUPP
whenever aca_handle_is_valid() evaluated to true.

Fix the logic in aca_handle_is_valid() to verify that the handle is
non-NULL, contains a valid mask, and is currently registered in the
list. Update amdgpu_aca_get_error_data() to check for invalid
handles and return 0 instead of -EOPNOTSUPP so non-ACA blocks in
global RAS queries pass through safely without breaking error
telemetry.

Additionally, update remove_aca_handle() to use list_del_init()
instead of list_del(). Standard list_del() leaves node pointers
poisoned, which causes !list_empty() in aca_handle_is_valid() to
evaluate to true for removed handles, leading to a potential
use-after-free during device teardown.

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_aca.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_aca.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_aca.c
index c76664af9902..06cb3ad1ce62 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_aca.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_aca.c
@@ -586,10 +586,7 @@ static int __aca_get_error_data(struct amdgpu_device *adev, struct aca_handle *h
 
 static bool aca_handle_is_valid(struct aca_handle *handle)
 {
-	if (!handle->mask || !list_empty(&handle->node))
-		return false;
-
-	return true;
+	return handle && handle->mask && !list_empty(&handle->node);
 }
 
 int amdgpu_aca_get_error_data(struct amdgpu_device *adev, struct aca_handle *handle,
@@ -599,8 +596,8 @@ int amdgpu_aca_get_error_data(struct amdgpu_device *adev, struct aca_handle *han
 	if (!handle || !err_data)
 		return -EINVAL;
 
-	if (aca_handle_is_valid(handle))
-		return -EOPNOTSUPP;
+	if (!aca_handle_is_valid(handle))
+		return 0;
 
 	if ((type < 0) || (!(BIT(type) & handle->mask)))
 		return  0;
@@ -717,7 +714,7 @@ static void remove_aca_handle(struct aca_handle *handle)
 	struct aca_handle_manager *mgr = handle->mgr;
 
 	aca_fini_error_cache(handle);
-	list_del(&handle->node);
+	list_del_init(&handle->node);
 	mgr->nr_handles--;
 }
 
-- 
2.54.0