linux-kernel - [PATCH] drm/msm: fix unbalanced DRM framebuffer init/destroy

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Date:	Tue,  5 May 2015 09:47:57 -0400
From:	Stephane Viau <sviau@...eaurora.org>
To:	dri-devel@...ts.freedesktop.org
Cc:	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	robdclark@...il.com, Stephane Viau <sviau@...eaurora.org>
Subject: [PATCH] drm/msm: fix unbalanced DRM framebuffer init/destroy

When msm_framebuffer_init() fails before calling drm_framebuffer_init(),
drm_framebuffer_cleanup() [called in msm_framebuffer_destroy()]
is still being called even though drm_framebuffer_init() was not
called for that buffer. Thus a NULL pointer derefencing:

[  247.529691] Unable to handle kernel NULL pointer dereference at virtual address 0000027c
...
[  247.563996] PC is at __mutex_lock_slowpath+0x94/0x3a8
...
[  247.823025] [<c07c3c78>] (__mutex_lock_slowpath) from [<c07c3fac>] (mutex_lock+0x20/0x3c)
[  247.831186] [<c07c3fac>] (mutex_lock) from [<c0347cf0>] (drm_framebuffer_cleanup+0x18/0x38)
[  247.839520] [<c0347cf0>] (drm_framebuffer_cleanup) from [<c036d138>] (msm_framebuffer_destroy+0x48/0x100)
[  247.849066] [<c036d138>] (msm_framebuffer_destroy) from [<c036d580>] (msm_framebuffer_init+0x1e8/0x228)
[  247.858439] [<c036d580>] (msm_framebuffer_init) from [<c036d630>] (msm_framebuffer_create+0x70/0x134)
[  247.867642] [<c036d630>] (msm_framebuffer_create) from [<c03493ec>] (internal_framebuffer_create+0x67c/0x7b4)
[  247.877537] [<c03493ec>] (internal_framebuffer_create) from [<c034ce34>] (drm_mode_addfb2+0x20/0x98)
[  247.886650] [<c034ce34>] (drm_mode_addfb2) from [<c034071c>] (drm_ioctl+0x240/0x420)
[  247.894378] [<c034071c>] (drm_ioctl) from [<c011df7c>] (do_vfs_ioctl+0x4e4/0x5a4)
...

Signed-off-by: Stephane Viau <sviau@...eaurora.org>
---
 drivers/gpu/drm/msm/msm_fb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_fb.c b/drivers/gpu/drm/msm/msm_fb.c
index 6b573e6..c0f09d3 100644
--- a/drivers/gpu/drm/msm/msm_fb.c
+++ b/drivers/gpu/drm/msm/msm_fb.c
@@ -239,8 +239,7 @@ struct drm_framebuffer *msm_framebuffer_init(struct drm_device *dev,
 	return fb;
 
 fail:
-	if (fb)
-		msm_framebuffer_destroy(fb);
+	kfree(msm_fb);
 
 	return ERR_PTR(ret);
 }
-- 
Qualcomm Innovation Center, Inc.

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project

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