linux-kernel - Re: [bpf-next] bpf: use kvmemdup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 9 Sep 2022 10:27:26 -0700
From:   sdf@...gle.com
To:     Wang Yufen <wangyufen@...wei.com>
Cc:     ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, kpsingh@...nel.org, haoluo@...gle.com,
        jolsa@...nel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [bpf-next] bpf: use kvmemdup_bpfptr helper

On 09/09, Wang Yufen wrote:
> Use kvmemdup_bpfptr helper instead of open-coding to
> simplify the code.

> Signed-off-by: Wang Yufen <wangyufen@...wei.com>
> ---
>   kernel/bpf/syscall.c | 14 ++++----------
>   1 file changed, 4 insertions(+), 10 deletions(-)

> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 4e9d4622aef7..13ce28081982 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1413,20 +1413,14 @@ static int map_update_elem(union bpf_attr *attr,  
> bpfptr_t uattr)
>   	}

>   	value_size = bpf_map_value_size(map);
> -
> -	err = -ENOMEM;
> -	value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN);
> -	if (!value)
> +	value = kvmemdup_bpfptr(uvalue, value_size);
> +	if (IS_ERR(value)) {
> +		err = PTR_ERR(value);
>   		goto free_key;
> -
> -	err = -EFAULT;
> -	if (copy_from_bpfptr(value, uvalue, value_size) != 0)
> -		goto free_value;
> +	}

>   	err = bpf_map_update_value(map, f, key, value, attr->flags);


[..]

> -free_value:
> -	kvfree(value);

And here you leak the value. We need to free it after update regardless
of error/success. That's why it is coded like that.

>   free_key:
>   	kvfree(key);
>   err_put:
> --
> 2.25.1