linux-kernel - [PATCH] drm: Fix a possible sleep-in-atomic bug in show

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Message-Id: <1513174943-18891-1-git-send-email-baijiaju1990@gmail.com>
Date:   Wed, 13 Dec 2017 22:22:23 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     daniel.vetter@...el.com, jani.nikula@...ux.intel.com,
        seanpaul@...omium.org, airlied@...ux.ie, dh.herrmann@...il.com
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] drm: Fix a possible sleep-in-atomic bug in show_leaks

The driver may sleep under a spinlock.
The function call path is:
drm_vma_offset_manager_destroy (acquire the spinlock)
  drm_mm_takedown
    show_leaks
      kmalloc(GFP_KERNEL) --> may sleep

To fix it, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool(DSAC) and checked by my code review.

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 61a1c8e..5b9965d 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;
 
-- 
1.7.9.5