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* [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()
@ 2018-09-01 12:20 Jia-Ju Bai
  2018-09-01 12:32 ` Chris Wilson
  0 siblings, 1 reply; 4+ messages in thread
From: Jia-Ju Bai @ 2018-09-01 12:20 UTC (permalink / raw)
  To: gustavo, maarten.lankhorst, seanpaul, airlied
  Cc: dri-devel, linux-kernel, Jia-Ju Bai

The driver may sleep with holding a spinlock.

The function call paths (from bottom to top) in Linux-4.16 are:

[FUNC] kmalloc(GFP_KERNEL)
drivers/gpu/drm/drm_mm.c, 130: 
	kmalloc in show_leaks
drivers/gpu/drm/drm_mm.c, 913: 
	show_leaks in drm_mm_takedown
drivers/gpu/drm/drm_vma_manager.c, 107: 
	drm_mm_takedown in drm_vma_offset_manager_destroy
drivers/gpu/drm/drm_vma_manager.c, 106: 
	_raw_write_lock in drm_vma_offset_manager_destroy

[FUNC] kmalloc(GFP_KERNEL)
drivers/gpu/drm/drm_mm.c, 130: 
	kmalloc in show_leaks
drivers/gpu/drm/drm_mm.c, 913: 
	show_leaks in drm_mm_takedown
drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 71: 
	drm_mm_takedown in amdgpu_vram_mgr_fini
drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 70: 
	spin_lock in amdgpu_vram_mgr_fini

[FUNC] kmalloc(GFP_KERNEL)
drivers/gpu/drm/drm_mm.c, 130: 
	kmalloc in show_leaks
drivers/gpu/drm/drm_mm.c, 913: 
	show_leaks in drm_mm_takedown
drivers/gpu/drm/ttm/ttm_bo_manager.c, 128: 
	drm_mm_takedown in ttm_bo_man_takedown
drivers/gpu/drm/ttm/ttm_bo_manager.c, 126: 
	spin_lock in ttm_bo_man_takedown

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/gpu/drm/drm_mm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 3166026a1874..2486121a78d4 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -127,7 +127,7 @@ static void show_leaks(struct drm_mm *mm)
 	unsigned long entries[STACKDEPTH];
 	char *buf;
 
-	buf = kmalloc(BUFSZ, GFP_KERNEL);
+	buf = kmalloc(BUFSZ, GFP_ATOMIC);
 	if (!buf)
 		return;
 
-- 
2.17.0


^ permalink raw reply related	[flat|nested] 4+ messages in thread

* Re: [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()
  2018-09-01 12:20 [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks() Jia-Ju Bai
@ 2018-09-01 12:32 ` Chris Wilson
  2018-09-03  7:52   ` Daniel Vetter
  0 siblings, 1 reply; 4+ messages in thread
From: Chris Wilson @ 2018-09-01 12:32 UTC (permalink / raw)
  To: Jia-Ju Bai, airlied, gustavo, maarten.lankhorst, seanpaul
  Cc: dri-devel, linux-kernel, Jia-Ju Bai

Quoting Jia-Ju Bai (2018-09-01 13:20:41)
> The driver may sleep with holding a spinlock.
> 
> The function call paths (from bottom to top) in Linux-4.16 are:
> 
> [FUNC] kmalloc(GFP_KERNEL)
> drivers/gpu/drm/drm_mm.c, 130: 
>         kmalloc in show_leaks
> drivers/gpu/drm/drm_mm.c, 913: 
>         show_leaks in drm_mm_takedown
> drivers/gpu/drm/drm_vma_manager.c, 107: 
>         drm_mm_takedown in drm_vma_offset_manager_destroy
> drivers/gpu/drm/drm_vma_manager.c, 106: 
>         _raw_write_lock in drm_vma_offset_manager_destroy
> 
> [FUNC] kmalloc(GFP_KERNEL)
> drivers/gpu/drm/drm_mm.c, 130: 
>         kmalloc in show_leaks
> drivers/gpu/drm/drm_mm.c, 913: 
>         show_leaks in drm_mm_takedown
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 71: 
>         drm_mm_takedown in amdgpu_vram_mgr_fini
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 70: 
>         spin_lock in amdgpu_vram_mgr_fini
> 
> [FUNC] kmalloc(GFP_KERNEL)
> drivers/gpu/drm/drm_mm.c, 130: 
>         kmalloc in show_leaks
> drivers/gpu/drm/drm_mm.c, 913: 
>         show_leaks in drm_mm_takedown
> drivers/gpu/drm/ttm/ttm_bo_manager.c, 128: 
>         drm_mm_takedown in ttm_bo_man_takedown
> drivers/gpu/drm/ttm/ttm_bo_manager.c, 126: 
>         spin_lock in ttm_bo_man_takedown
> 
> To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

The bug are above, since those spinlocks do not protect the data and
imply use-after-free.
-Chris

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()
  2018-09-01 12:32 ` Chris Wilson
@ 2018-09-03  7:52   ` Daniel Vetter
  2018-09-03 12:05     ` Christian König
  0 siblings, 1 reply; 4+ messages in thread
From: Daniel Vetter @ 2018-09-03  7:52 UTC (permalink / raw)
  To: Chris Wilson
  Cc: Jia-Ju Bai, airlied, gustavo, maarten.lankhorst, seanpaul,
	linux-kernel, dri-devel, Alex Deucher, amd-gfx, David Zhou,
	Christian König

On Sat, Sep 01, 2018 at 01:32:54PM +0100, Chris Wilson wrote:
> Quoting Jia-Ju Bai (2018-09-01 13:20:41)
> > The driver may sleep with holding a spinlock.
> > 
> > The function call paths (from bottom to top) in Linux-4.16 are:
> > 
> > [FUNC] kmalloc(GFP_KERNEL)
> > drivers/gpu/drm/drm_mm.c, 130: 
> >         kmalloc in show_leaks
> > drivers/gpu/drm/drm_mm.c, 913: 
> >         show_leaks in drm_mm_takedown
> > drivers/gpu/drm/drm_vma_manager.c, 107: 
> >         drm_mm_takedown in drm_vma_offset_manager_destroy
> > drivers/gpu/drm/drm_vma_manager.c, 106: 
> >         _raw_write_lock in drm_vma_offset_manager_destroy
> > 
> > [FUNC] kmalloc(GFP_KERNEL)
> > drivers/gpu/drm/drm_mm.c, 130: 
> >         kmalloc in show_leaks
> > drivers/gpu/drm/drm_mm.c, 913: 
> >         show_leaks in drm_mm_takedown
> > drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 71: 
> >         drm_mm_takedown in amdgpu_vram_mgr_fini
> > drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 70: 
> >         spin_lock in amdgpu_vram_mgr_fini
> > 
> > [FUNC] kmalloc(GFP_KERNEL)
> > drivers/gpu/drm/drm_mm.c, 130: 
> >         kmalloc in show_leaks
> > drivers/gpu/drm/drm_mm.c, 913: 
> >         show_leaks in drm_mm_takedown
> > drivers/gpu/drm/ttm/ttm_bo_manager.c, 128: 
> >         drm_mm_takedown in ttm_bo_man_takedown
> > drivers/gpu/drm/ttm/ttm_bo_manager.c, 126: 
> >         spin_lock in ttm_bo_man_takedown
> > 
> > To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
> 
> The bug are above, since those spinlocks do not protect the data and
> imply use-after-free.

Adding amdgpu, since that's where the bug seems to be.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()
  2018-09-03  7:52   ` Daniel Vetter
@ 2018-09-03 12:05     ` Christian König
  0 siblings, 0 replies; 4+ messages in thread
From: Christian König @ 2018-09-03 12:05 UTC (permalink / raw)
  To: Chris Wilson, Jia-Ju Bai, airlied, gustavo, maarten.lankhorst,
	seanpaul, linux-kernel, dri-devel, Alex Deucher, amd-gfx,
	David Zhou, Christian König

Am 03.09.2018 um 09:52 schrieb Daniel Vetter:
> On Sat, Sep 01, 2018 at 01:32:54PM +0100, Chris Wilson wrote:
>> Quoting Jia-Ju Bai (2018-09-01 13:20:41)
>>> The driver may sleep with holding a spinlock.
>>>
>>> The function call paths (from bottom to top) in Linux-4.16 are:
>>>
>>> [FUNC] kmalloc(GFP_KERNEL)
>>> drivers/gpu/drm/drm_mm.c, 130:
>>>          kmalloc in show_leaks
>>> drivers/gpu/drm/drm_mm.c, 913:
>>>          show_leaks in drm_mm_takedown
>>> drivers/gpu/drm/drm_vma_manager.c, 107:
>>>          drm_mm_takedown in drm_vma_offset_manager_destroy
>>> drivers/gpu/drm/drm_vma_manager.c, 106:
>>>          _raw_write_lock in drm_vma_offset_manager_destroy
>>>
>>> [FUNC] kmalloc(GFP_KERNEL)
>>> drivers/gpu/drm/drm_mm.c, 130:
>>>          kmalloc in show_leaks
>>> drivers/gpu/drm/drm_mm.c, 913:
>>>          show_leaks in drm_mm_takedown
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 71:
>>>          drm_mm_takedown in amdgpu_vram_mgr_fini
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 70:
>>>          spin_lock in amdgpu_vram_mgr_fini
>>>
>>> [FUNC] kmalloc(GFP_KERNEL)
>>> drivers/gpu/drm/drm_mm.c, 130:
>>>          kmalloc in show_leaks
>>> drivers/gpu/drm/drm_mm.c, 913:
>>>          show_leaks in drm_mm_takedown
>>> drivers/gpu/drm/ttm/ttm_bo_manager.c, 128:
>>>          drm_mm_takedown in ttm_bo_man_takedown
>>> drivers/gpu/drm/ttm/ttm_bo_manager.c, 126:
>>>          spin_lock in ttm_bo_man_takedown
>>>
>>> To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
>> The bug are above, since those spinlocks do not protect the data and
>> imply use-after-free.
> Adding amdgpu, since that's where the bug seems to be.

When we have use after free we might have concurrent uses as well.

I think taking the lock here is probably a good idea if you don't want 
to accidentally access freed memory in show_leaks.

So Chris change sounds valid to me.

Christian.

> -Daniel


^ permalink raw reply	[flat|nested] 4+ messages in thread

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2018-09-01 12:20 [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks() Jia-Ju Bai
2018-09-01 12:32 ` Chris Wilson
2018-09-03  7:52   ` Daniel Vetter
2018-09-03 12:05     ` Christian König

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