linux-kernel - Re: [PATCH] loop: fix backing file reference leak on validation error

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Message-ID: <68aebe91-4dcd-925f-4232-1c432fe6899d@huaweicloud.com>
Date: Mon, 29 Sep 2025 09:11:04 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Li Chen <me@...ux.beauty>, Jens Axboe <axboe@...nel.dk>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] loop: fix backing file reference leak on validation error

Hi,

在 2025/09/26 20:12, Li Chen 写道:
> loop_change_fd() and loop_configure() call loop_check_backing_file()
> to validate the new backing file. If validation fails, the reference
> acquired by fget() was not dropped, leaking a file reference.
> 
> Fix this by calling fput(file) before returning the error.
> 
> Signed-off-by: Li Chen <chenl311@...natelecom.cn>
> ---
>   drivers/block/loop.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 053a086d547e..94ec7f747f36 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -551,8 +551,10 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
>   		return -EBADF;
>   
>   	error = loop_check_backing_file(file);
> -	if (error)
> +	if (error) {
> +		fput(file);
>   		return error;
> +	}
>   
>   	/* suppress uevents while reconfiguring the device */
>   	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
> @@ -993,8 +995,10 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
>   		return -EBADF;
>   
>   	error = loop_check_backing_file(file);
> -	if (error)
> +	if (error) {
> +		fput(file);
>   		return error;
> +	}
>   
>   	is_loop = is_loop_device(file);
>   
> 

The changes look correct, however, I'll prefer to change the error path
to the reverse order and add a new error tag.

Thanks,
Kuai