linux-kernel - [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show

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Message-Id: <20180901122041.2357-1-baijiaju1990@gmail.com>
Date:   Sat,  1 Sep 2018 20:20:41 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     gustavo@...ovan.org, maarten.lankhorst@...ux.intel.com,
        seanpaul@...omium.org, airlied@...ux.ie
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()

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@...il.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