Re: [PATCH] drm/amdkfd: potential crash in kfd_create_indirect_link_prop()

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On 2022-08-12 02:20, Dan Carpenter wrote:
This code has two bugs.  If kfd_topology_device_by_proximity_domain()
failed on the first iteration through the loop then "cpu_link" is
uninitialized and should not be dereferenced.

The second bug is that we cannot dereference a list iterator when it
points to the list head.  In other words, if we exit the
list_for_each_entry() loop exits without hitting a break then "cpu_link"
is not a valid pointer and should not be dereferenced.

Fix both of these problems by setting "cpu_link" to NULL when it is invalid
and non-NULL when it is valid.  That makes it easier to test for
valid vs invalid.

Fixes: 0f28cca87e9a ("drm/amdkfd: Extend KFD device topology to surface peer-to-peer links")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
I reported these in June but never heard back.

I thought Ramesh implemented a fix for this: https://lore.kernel.org/all/20220706183302.1719795-1-Ramesh.Errabolu@xxxxxxx/

You commented on a version of his patch: https://lore.kernel.org/all/20220629161241.GM11460@kadam/

Did this get lost somehow? Anyway, your patch looks good to me and I'm going to apply it to amd-staging-drm-next now.

Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>

Thanks,
  Felix



  drivers/gpu/drm/amd/amdkfd/kfd_topology.c | 11 +++++++----
  1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
index 25990bec600d..3f0a4a415907 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
@@ -1392,8 +1392,8 @@ static int kfd_build_p2p_node_entry(struct kfd_topology_device *dev,
static int kfd_create_indirect_link_prop(struct kfd_topology_device *kdev, int gpu_node)
  {
+	struct kfd_iolink_properties *gpu_link, *tmp_link, *cpu_link;
  	struct kfd_iolink_properties *props = NULL, *props2 = NULL;
-	struct kfd_iolink_properties *gpu_link, *cpu_link;
  	struct kfd_topology_device *cpu_dev;
  	int ret = 0;
  	int i, num_cpu;
@@ -1416,16 +1416,19 @@ static int kfd_create_indirect_link_prop(struct kfd_topology_device *kdev, int g
  			continue;
/* find CPU <--> CPU links */
+		cpu_link = NULL;
  		cpu_dev = kfd_topology_device_by_proximity_domain(i);
  		if (cpu_dev) {
-			list_for_each_entry(cpu_link,
+			list_for_each_entry(tmp_link,
  					&cpu_dev->io_link_props, list) {
-				if (cpu_link->node_to == gpu_link->node_to)
+				if (tmp_link->node_to == gpu_link->node_to) {
+					cpu_link = tmp_link;
  					break;
+				}
  			}
  		}
- if (cpu_link->node_to != gpu_link->node_to)
+		if (!cpu_link)
  			return -ENOMEM;
/* CPU <--> CPU <--> GPU, GPU node*/



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