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Subject[PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()
Date
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
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