netdev - Re: [PATCH 2/3] bpf: simplify if-if to if in bpf_kprobe_multi_link

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Date:   Thu, 12 May 2022 16:44:30 +0000
From:   Song Liu <songliubraving@...com>
To:     Wan Jiabing <wanjiabing@...o.com>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] bpf: simplify if-if to if in
 bpf_kprobe_multi_link_attach



> On May 12, 2022, at 7:17 AM, Wan Jiabing <wanjiabing@...o.com> wrote:
> 
> Simplify double 'if' statements to one 'if' statement.
> 
> Signed-off-by: Wan Jiabing <wanjiabing@...o.com>
> ---
> kernel/trace/bpf_trace.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 3a8b69ef9a0d..1b0db8f78dc8 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -2464,11 +2464,9 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
> 	if (!addrs)
> 		return -ENOMEM;
> 
> -	if (uaddrs) {
> -		if (copy_from_user(addrs, uaddrs, size)) {
> -			err = -EFAULT;
> -			goto error_addrs;
> -		}
> +	if (uaddrs && copy_from_user(addrs, uaddrs, size)) {
> +		err = -EFAULT;
> +		goto error_addrs;
> 	} else {
> 		struct user_syms us;

This changed the behavior, no?

For uaddrs != NULL and copy_from_user() == 0 case, we now going into
else clause. Did I misread anything?

Song