linux-kernel - [PATCH] gma500: Fix possible sleep-in-atomic bugs in gma_power

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Date:   Mon,  9 Oct 2017 18:06:17 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     patrik.r.jakobsson@...il.com, airlied@...ux.ie,
        gregkh@...uxfoundation.org
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@....com>
Subject: [PATCH] gma500: Fix possible sleep-in-atomic bugs in gma_power_begin

The driver may sleep under a spinlock, and the function call paths are:
gma_power_begin (acquire the spinlock) (drivers/gpu/drm/gma500/power.c)
   gma_resume_pci
     pci_set_power_state
       __pci_start_power_transition (drivers/pci/pci.c)
         msleep --> may sleep

gma_power_begin (acquire the spinlock) (drivers/gpu/drm/gma500/power.c)
   gma_resume_pci
     pci_enable_device
       pci_enable_device_flags (drivers/pci/pci.c)
         do_pci_enable_device
           pci_set_power_state
             __pci_start_power_transition
               msleep --> may sleep 

To fix them, the spinlock is released before gma_resume_pci, and it is acquired again after gma_resume_pci.

This bug is found by my static analysis tool and my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
---
 drivers/gpu/drm/gma500/power.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/gma500/power.c b/drivers/gpu/drm/gma500/power.c
index bea8578..c355d7e 100644
--- a/drivers/gpu/drm/gma500/power.c
+++ b/drivers/gpu/drm/gma500/power.c
@@ -264,7 +264,9 @@ bool gma_power_begin(struct drm_device *dev, bool force_on)
 		goto out_false;
 
 	/* Ok power up needed */
+	spin_unlock_irqrestore(&power_ctrl_lock, flags);
 	ret = gma_resume_pci(dev->pdev);
+	spin_lock_irqsave(&power_ctrl_lock, flags);
 	if (ret == 0) {
 		psb_irq_preinstall(dev);
 		psb_irq_postinstall(dev);
-- 
1.7.9.5