Re: [PATCH] drm/amdgpu: disallow multiple BO_HANDLES chunks in one submit

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Am 03.07.24 um 14:48 schrieb Pierre-Eric Pelloux-Prayer:
Le 02/07/2024 à 15:35, Christian König a écrit :
Am 02.07.24 um 15:23 schrieb Pierre-Eric Pelloux-Prayer:
Before this commit, only submits with both a BO_HANDLES chunk and a
'bo_list_handle' would be rejected (by amdgpu_cs_parser_bos).

But if UMD sent a multiple BO_HANDLES, what would happen is:
* only the last one would be really used
* all the others would leak memory as amdgpu_cs_p1_bo_handles would
   overwrite the previous p->bo_list value

This commit rejects submissions with multiple BO_HANDLES chunks to
match the implementation of the parser.

Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@xxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index c08dfffae262..69d168d6f35a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -154,6 +154,10 @@ static int amdgpu_cs_p1_bo_handles(struct amdgpu_cs_parser *p,
      struct drm_amdgpu_bo_list_entry *info;
      int r;
+    /* Disallow multiple BO_HANDLES chunks. */

Describe why you do something, instead of what you do since that should be obvious from the code.

E.g. something like /* Only allow a single BO list to avoid memory leak. */

It's not really to avoid a memleak because the code below could be fixed
to not leak the list.
This change is really about only disallowing multiple BO_HANDLES since this is the de-facto API, except it was not validated until now.

I can rephrase the comment as /* Only a single BO list is allowed. */

Would that work?

Mhm, we still need to give a reason why only a single BO list is allowed.

Maybe "Only a single BO list is allowed to simplify handling".

I don't really see a use case for having more than one BO list, but who knows.

Regards,
Christian.


Thanks,
Pierre-Eric


With that fixed Reviewed-by: Christian König <christian.koenig@xxxxxxx>

Regards,
Christian.


+    if (p->bo_list)
+        return -EINVAL;
+
      r = amdgpu_bo_create_list_entry_array(data, &info);
      if (r)
          return r;




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