netdev - Re: [PATCH v8 4/8] bpftool: Ensure task comm is always NUL-terminated

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Message-ID: <ozoyqz5a7zssggowambojv4x6fbhdl6iqjopgnycca223jm6sz@pdzdmshhdgwn>
Date: Thu, 12 Sep 2024 14:14:47 -0700
From: Justin Stitt <justinstitt@...gle.com>
To: Yafang Shao <laoar.shao@...il.com>
Cc: akpm@...ux-foundation.org, torvalds@...ux-foundation.org, 
	alx@...nel.org, ebiederm@...ssion.com, alexei.starovoitov@...il.com, 
	rostedt@...dmis.org, catalin.marinas@....com, penguin-kernel@...ove.sakura.ne.jp, 
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, audit@...r.kernel.org, linux-security-module@...r.kernel.org, 
	selinux@...r.kernel.org, bpf@...r.kernel.org, netdev@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, Quentin Monnet <qmo@...nel.org>
Subject: Re: [PATCH v8 4/8] bpftool: Ensure task comm is always NUL-terminated

Hi,

On Wed, Aug 28, 2024 at 11:03:17AM GMT, Yafang Shao wrote:
> Let's explicitly ensure the destination string is NUL-terminated. This way,
> it won't be affected by changes to the source string.
> 
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> Reviewed-by: Quentin Monnet <qmo@...nel.org>
> ---
>  tools/bpf/bpftool/pids.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c
> index 9b898571b49e..23f488cf1740 100644
> --- a/tools/bpf/bpftool/pids.c
> +++ b/tools/bpf/bpftool/pids.c
> @@ -54,6 +54,7 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
>  		ref = &refs->refs[refs->ref_cnt];
>  		ref->pid = e->pid;
>  		memcpy(ref->comm, e->comm, sizeof(ref->comm));
> +		ref->comm[sizeof(ref->comm) - 1] = '\0';

...

>  		refs->ref_cnt++;
>  
>  		return;
> @@ -77,6 +78,7 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
>  	ref = &refs->refs[0];
>  	ref->pid = e->pid;
>  	memcpy(ref->comm, e->comm, sizeof(ref->comm));
> +	ref->comm[sizeof(ref->comm) - 1] = '\0';

Excuse my ignorance, do we not have a strscpy() equivalent usable in bpf
code?

>  	refs->ref_cnt = 1;
>  	refs->has_bpf_cookie = e->has_bpf_cookie;
>  	refs->bpf_cookie = e->bpf_cookie;
> -- 
> 2.43.5
> 

Thanks
Justin