[PATCH master] block: fix calling cdev_get_block_device with partitions

[PATCH master] block: fix calling cdev_get_block_device with partitions

[Ahmad Fatoum]

For partitions, cdev->priv references the parent block device.
Doing the pointer arithmetic in container_of will result in an
out-of-bounds access. Do what the rest of the code does
and access cdev->priv instead.

Fixes: 84173bf3d0cc ("block: set S_IFBLK for block devices instead of S_IFCHR")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 common/block.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/block.c b/common/block.c
index 19bb81df2c3d..a4cfd6e22771 100644
--- a/common/block.c
+++ b/common/block.c
@@ -366,7 +366,7 @@ struct block_device *cdev_get_block_device(struct cdev *cdev)
 	if (!cdev || cdev->ops != &block_ops)
 		return NULL;
 
-	return container_of(cdev, struct block_device, cdev);
+	return cdev->priv;
 }
 
 int blockdevice_register(struct block_device *blk)
-- 
2.30.2

Re: [PATCH master] block: fix calling cdev_get_block_device with partitions

[Sascha Hauer]

On Mon, Oct 10, 2022 at 08:38:34AM +0200, Ahmad Fatoum wrote:
> For partitions, cdev->priv references the parent block device.
> Doing the pointer arithmetic in container_of will result in an
> out-of-bounds access. Do what the rest of the code does
> and access cdev->priv instead.
> 
> Fixes: 84173bf3d0cc ("block: set S_IFBLK for block devices instead of S_IFCHR")
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  common/block.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks

Sascha

> 
> diff --git a/common/block.c b/common/block.c
> index 19bb81df2c3d..a4cfd6e22771 100644
> --- a/common/block.c
> +++ b/common/block.c
> @@ -366,7 +366,7 @@ struct block_device *cdev_get_block_device(struct cdev *cdev)
>  	if (!cdev || cdev->ops != &block_ops)
>  		return NULL;
>  
> -	return container_of(cdev, struct block_device, cdev);
> +	return cdev->priv;
>  }
>  
>  int blockdevice_register(struct block_device *blk)
> -- 
> 2.30.2
> 
> 
> 

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