lkml.org 
[lkml]   [2019]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2] media: rga: fix NULL pointer dereferences and a memory leak
From
Date
On 12/03/2019 06:58, Kangjie Lu wrote:
> In case __get_free_pages fails, the fix releases resources and
> return -ENOMEM to avoid NULL pointer dereferences.
>
> Also, the fix frees pages when video_register_device fails to
> avoid a memory leak.
>
> Signed-off-by: Kangjie Lu <kjlu@umn.edu>
> ---
> drivers/media/platform/rockchip/rga/rga.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
> index 5c653287185f..307b7ab0ab64 100644
> --- a/drivers/media/platform/rockchip/rga/rga.c
> +++ b/drivers/media/platform/rockchip/rga/rga.c
> @@ -892,8 +892,17 @@ static int rga_probe(struct platform_device *pdev)
>
> rga->src_mmu_pages =
> (unsigned int *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 3);
> + if (!rga->src_mmu_pages) {
> + ret = -ENOMEM;
> + goto rel_vdev;
> + }
> +
> rga->dst_mmu_pages =
> (unsigned int *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 3);
> + if (!rga->dst_mmu_pages) {
> + ret = -ENOMEM;
> + goto free_dst_pages;
> + }
>
> def_frame.stride = (def_frame.width * def_frame.fmt->depth) >> 3;
> def_frame.size = def_frame.stride * def_frame.height;
> @@ -901,7 +910,7 @@ static int rga_probe(struct platform_device *pdev)
> ret = video_register_device(vfd, VFL_TYPE_GRABBER, -1);
> if (ret) {
> v4l2_err(&rga->v4l2_dev, "Failed to register video device\n");
> - goto rel_vdev;
> + goto free_pages;
> }
>
> v4l2_info(&rga->v4l2_dev, "Registered %s as /dev/%s\n",
> @@ -909,6 +918,10 @@ static int rga_probe(struct platform_device *pdev)
>
> return 0;
>
> +free_pages:
> + free_pages((unsigned long)rga->src_mmu_pages, 3);
> +free_dst_pages:
> + free_pages((unsigned long)rga->dst_mmu_pages, 3);
> rel_vdev:
> video_device_release(vfd);
> unreg_video_dev:

That looks good. However looking into the error path more closely it
appears that this was already rather broken. Here's the original:

> rel_vdev:
> video_device_release(vfd);
> unreg_video_dev:
> video_unregister_device(rga->vfd);
> unreg_v4l2_dev:
> v4l2_device_unregister(&rga->v4l2_dev);
> err_put_clk:
> pm_runtime_disable(rga->dev);

video_device_release() is simply a call to kfree(), but
video_unregister_device will then be called with the same pointer
(rga->vfd is set to vfd further up). Which will then cause a
use-after-free on the pointer.

It might be a good idea to test this error path, for example make the
video_register_device() call always fail and run with memory debuggers
enabled (e.g. CONFIG_KASAN or CONFIG_DEBUG_KMEM_LEAK).

Steve

\
 
 \ /
  Last update: 2019-03-13 14:36    [W:0.081 / U:3.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site