Re: [PATCH] drm/amdgpu: Fix the page fault issue in amdgpu_irq_fini

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Am 19.03.21 um 02:38 schrieb Deng, Emily:
[AMD Official Use Only - Internal Distribution Only]

-----Original Message-----
From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
Sent: Thursday, March 18, 2021 7:52 PM
To: Deng, Emily <Emily.Deng@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH] drm/amdgpu: Fix the page fault issue in amdgpu_irq_fini

Am 18.03.21 um 12:48 schrieb Emily Deng:
For some source, it will be shared by some client ID and source ID.
To fix the page fault issue, set all those to null.

Signed-off-by: Emily Deng <Emily.Deng@xxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c | 16 +++++++++++++---
   1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
index af026109421a..623b1ac6231d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c
@@ -359,7 +359,7 @@ int amdgpu_irq_init(struct amdgpu_device *adev)
    */
   void amdgpu_irq_fini(struct amdgpu_device *adev)
   {
-unsigned i, j;
+unsigned i, j, m, n;

   if (adev->irq.installed) {
   drm_irq_uninstall(adev_to_drm(adev));
@@ -380,12 +380,22 @@ void amdgpu_irq_fini(struct amdgpu_device
*adev)
   if (!src)
   continue;

-kfree(src->enabled_types);
+if (src->enabled_types)
+kfree(src->enabled_types);
A NULL check before kfree() is unecessary and will be complained about by the
static checkers.
Sorry, will remove this.
+
   src->enabled_types = NULL;
+
Unrelated white space change.
Sorry, will remove this also.
   if (src->data) {
   kfree(src->data);
   kfree(src);
-adev->irq.client[i].sources[j] = NULL;
+}
+
+for (m = 0; m < AMDGPU_IRQ_CLIENTID_MAX; ++m) {
+if (!adev->irq.client[m].sources)
+continue;
+for (n = 0; n < AMDGPU_MAX_IRQ_SRC_ID;
++n)
+if (adev->irq.client[m].sources[n] ==
src)
+adev->irq.client[m].sources[n]
= NULL;

Hui what? The memory you set to NULL here is freed on the line below.

Accessing it after that would be illegal, so why do you want to set it to NULL?
[Emily] It is in the loop "for (j = 0; j < AMDGPU_MAX_IRQ_SRC_ID; ++j) {", shouldn't have been freed in this loop. Only set " adev->irq.client[i].sources[j] = NULL;" is not enough,
as it maybe have other client ID and src ID will share the same src. Also need to set those to NULL.

No, that can't happen.

It is illegal to use a dynamic allocated source with multiple client ID and src ID. Where do you see that?

We could also probably completely remove this feature since it is unused as far as I know.

Thanks,
Christian.

Christian.

   }
   }
   kfree(adev->irq.client[i].sources);

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