linux-kernel - [PATCHv2] media: videobuf2-dma-contig: fix bad kfree in vb2_dma_contig_clear_max_seg

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Message-ID: <20200527082334.20774-1-tomi.valkeinen@ti.com>
Date:   Wed, 27 May 2020 11:23:34 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Linux Media Mailing List <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        <stable@...r.kernel.org>
Subject: [PATCHv2] media: videobuf2-dma-contig: fix bad kfree in vb2_dma_contig_clear_max_seg_size

Commit 9495b7e92f716ab2bd6814fab5e97ab4a39adfdd ("driver core: platform:
Initialize dma_parms for platform devices") in v5.7-rc5 causes
vb2_dma_contig_clear_max_seg_size() to kfree memory that was not
allocated by vb2_dma_contig_set_max_seg_size().

The assumption in vb2_dma_contig_set_max_seg_size() seems to be that
dev->dma_parms is always NULL when the driver is probed, and the case
where dev->dma_parms has bee initialized by someone else than the driver
(by calling vb2_dma_contig_set_max_seg_size) will cause a failure.

All the current users of these functions are platform devices, which now
always have dma_parms set by the driver core. To fix the issue for v5.7,
make vb2_dma_contig_set_max_seg_size() return an error if dma_parms is
NULL to be on the safe side, and remove the kfree code from
vb2_dma_contig_clear_max_seg_size().

For v5.8 we should remove the two functions and move the
dma_set_max_seg_size() calls into the drivers.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
Fixes: 9495b7e92f71 ("driver core: platform: Initialize dma_parms for platform devices")
Cc: stable@...r.kernel.org
---

Changes in v2:
* vb2_dma_contig_clear_max_seg_size to empty static inline
* Added cc: stable and fixes tag

 .../common/videobuf2/videobuf2-dma-contig.c   | 20 ++-----------------
 include/media/videobuf2-dma-contig.h          |  2 +-
 2 files changed, 3 insertions(+), 19 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index d3a3ee5b597b..f4b4a7c135eb 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -726,9 +726,8 @@ EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
 int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
 {
 	if (!dev->dma_parms) {
-		dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
-		if (!dev->dma_parms)
-			return -ENOMEM;
+		dev_err(dev, "Failed to set max_seg_size: dma_parms is NULL\n");
+		return -ENODEV;
 	}
 	if (dma_get_max_seg_size(dev) < size)
 		return dma_set_max_seg_size(dev, size);
@@ -737,21 +736,6 @@ int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
 }
 EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
 
-/*
- * vb2_dma_contig_clear_max_seg_size() - release resources for DMA parameters
- * @dev:	device for configuring DMA parameters
- *
- * This function releases resources allocated to configure DMA parameters
- * (see vb2_dma_contig_set_max_seg_size() function). It should be called from
- * device drivers on driver remove.
- */
-void vb2_dma_contig_clear_max_seg_size(struct device *dev)
-{
-	kfree(dev->dma_parms);
-	dev->dma_parms = NULL;
-}
-EXPORT_SYMBOL_GPL(vb2_dma_contig_clear_max_seg_size);
-
 MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
 MODULE_AUTHOR("Pawel Osciak <pawel@...iak.com>");
 MODULE_LICENSE("GPL");
diff --git a/include/media/videobuf2-dma-contig.h b/include/media/videobuf2-dma-contig.h
index 5604818d137e..5be313cbf7d7 100644
--- a/include/media/videobuf2-dma-contig.h
+++ b/include/media/videobuf2-dma-contig.h
@@ -25,7 +25,7 @@ vb2_dma_contig_plane_dma_addr(struct vb2_buffer *vb, unsigned int plane_no)
 }
 
 int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size);
-void vb2_dma_contig_clear_max_seg_size(struct device *dev);
+static inline void vb2_dma_contig_clear_max_seg_size(struct device *dev) { }
 
 extern const struct vb2_mem_ops vb2_dma_contig_memops;
 
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