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AJvYcCWfmC0oUFus7AGAOv8tTa7MhhEfFRmuM0LQeP0d/bm1PpUirB7J3N3j5h/PHZj6wxZSZr9/fengtXMY7KaF7LzlP63Xf5xhr0A2NkIOWZMFNa4lcqKRKH+kfCzzrHSpkCw7dz5/xU1c5qpkRzdkrsMOwyVVvBEtmJMR2/x486xvW2QbbjenKzjfof4uf0PkLA4m5zjGevgRnYC34KIFFiFg5XPXO09vg4lPasglN2ivFh1vRX05HaDAmI0I4WZMMTMMdufkpMZzFF1c/hyhmVPaxaEwFvuB+J4yLsmN2A7x/n8YGhWYYRFrT/+6un0UY5fQJwGzMQ== X-Gm-Message-State: AOJu0YwFWnJteLc7LVrcW325GHdf9sVR/h4JRPWW5iAymluJRgm7xrs5 rR7Md3aRLMzYVV1xkK7heHWtocGABbMGyBka9AGguV6SVNIYlmS9Qd+hhdpiwa5VZHgOz/MGDMM on42UBFOi2egJhVHF7m4d5hv8QkE= X-Google-Smtp-Source: AGHT+IF6fsYhsqIGmUj8T8nAX8ZPHa9aPPiBT0MCECGu/PEHdrCH4USnvIhXgIzMD1DqBj/lqnH5UAtX5RLYSKjl0r4= X-Received: by 2002:ad4:5894:0:b0:6bf:7ae1:9a8f with SMTP id 6a1803df08f44-6bf7ae19b89mr122178546d6.19.1723948061122; Sat, 17 Aug 2024 19:27:41 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240817025624.13157-1-laoar.shao@gmail.com> <20240817025624.13157-5-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Sun, 18 Aug 2024 10:27:01 +0800 Message-ID: Subject: Re: [PATCH v7 4/8] bpftool: Ensure task comm is always NUL-terminated To: Alejandro Colomar Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, justinstitt@google.com, ebiederm@xmission.com, alexei.starovoitov@gmail.com, rostedt@goodmis.org, catalin.marinas@arm.com, penguin-kernel@i-love.sakura.ne.jp, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, audit@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Quentin Monnet Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sat, Aug 17, 2024 at 4:39=E2=80=AFPM Alejandro Colomar = wrote: > > Hi Yafang, > > On Sat, Aug 17, 2024 at 10:56:20AM 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 > > Reviewed-by: Quentin Monnet > > --- > > 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_i= ter_entry *e) > > ref =3D &refs->refs[refs->ref_cnt]; > > ref->pid =3D e->pid; > > memcpy(ref->comm, e->comm, sizeof(ref->comm)); > > + ref->comm[sizeof(ref->comm) - 1] =3D '\0'; > > Why doesn't this use strscpy()? bpftool is a userspace tool, so strscpy() is only applicable in kernel code, correct? > Isn't the source terminated? It is currently terminated, but I believe we should avoid relying on the source. Making it independent of the source would reduce potential errors. > > Both the source and the destination measure 16 characters. If it is > true that the source is not terminated, then this copy might truncate > the (non-)string by overwriting the last byte with a NUL. Is that > truncation a good thing? It's not ideal, but we should still convert it to a string, even if it ends up being truncated. -- Regards Yafang