linux-kernel - RE: [PATCH V2] net: bpf: switch over to memdup

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Date:   Mon, 18 Oct 2021 09:26:49 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Qing Wang <wangqing@...o.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Qing Wang <wangqing@...o.com>
Subject: RE: [PATCH V2] net: bpf: switch over to memdup_user()

Qing Wang wrote:
> This patch fixes the following Coccinelle warning:
> 
> net/bpf/test_run.c:361:8-15: WARNING opportunity for memdup_user
> net/bpf/test_run.c:1055:8-15: WARNING opportunity for memdup_user
> 
> Use memdup_user rather than duplicating its implementation
> This is a little bit restricted to reduce false positives
> 
> Signed-off-by: Qing Wang <wangqing@...o.com>
> ---
>  net/bpf/test_run.c | 21 ++++++---------------
>  1 file changed, 6 insertions(+), 15 deletions(-)

LGTM, but subject line should be '[PATCH bpf-next v2]' there is no reason
to push to fixes trees here.

Also might be worth noting that the original kzalloc could have just been
a kalloc because copy_from_user will zero any extra bytes.

Acked-by: John Fastabend <john.fastabend@...il.com>

> 
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index 5296087..fbda8f5
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -358,13 +358,9 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
>  		return -EINVAL;
>  
>  	if (ctx_size_in) {
> -		info.ctx = kzalloc(ctx_size_in, GFP_USER);
> -		if (!info.ctx)
> -			return -ENOMEM;
> -		if (copy_from_user(info.ctx, ctx_in, ctx_size_in)) {
> -			err = -EFAULT;
> -			goto out;
> -		}
> +		info.ctx = memdup_user(ctx_in, ctx_size_in);
> +		if (IS_ERR(info.ctx))
> +			return PTR_ERR(info.ctx);
>  	} else {
>  		info.ctx = NULL;
>  	}
> @@ -392,7 +388,6 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
>  	    copy_to_user(&uattr->test.retval, &info.retval, sizeof(u32)))
>  		err = -EFAULT;
>  
> -out:
>  	kfree(info.ctx);
>  	return err;
>  }
> @@ -1052,13 +1047,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
>  		return -EINVAL;
>  
>  	if (ctx_size_in) {
> -		ctx = kzalloc(ctx_size_in, GFP_USER);
> -		if (!ctx)
> -			return -ENOMEM;
> -		if (copy_from_user(ctx, ctx_in, ctx_size_in)) {
> -			err = -EFAULT;
> -			goto out;
> -		}
> +		ctx = memdup_user(ctx_in, ctx_size_in);
> +		if (IS_ERR(ctx))
> +			return PTR_ERR(ctx);
>  	}
>  
>  	rcu_read_lock_trace();
> -- 
> 2.7.4
>