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AJvYcCVBvw4MnCNF2J5BPfhrk08xdwYJ2DkE5y8cjoP0IFNa99SqhN/DqCGa/gA7as1KkR60zhKeC7RLRSbtYlPOYZ5RzIg= X-Gm-Message-State: AOJu0Yxd+3msJ/xz7hZt9KkGOIn7Rvx0KIBotdWaMCnKawsvjmV/kX86 fjOMKgp42M2JddE9t0XwpZgZbnfP33DukE1lS9nUGGbB1zJVDBAhnPr9q50wS9IwmE0S8nnyLNA KyWsYHe7mr8UoT5sh6fLW3hkYby0= 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) 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 X-Stat-Signature: z9478njkxg11wn1ecbkzsi1d1yw4c936 X-Rspam-User: X-Rspamd-Queue-Id: 146E0C0010 X-Rspamd-Server: rspam02 X-HE-Tag: 1723948061-674425 X-HE-Meta: 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 z++tY7Uk hP3BhU7L2o1o+r7e157UJXDhFo3C2uAj8snXul8LrMqIdc5m2R+mYB4rN3PaEcqDiALSkuRktuSG39pLjLeEHzH9DotulAvb/0KNbV396J2HgaMda/e6g4ZWl/vAv1PoFvN18uKpA35Ak2e78QIKSbyyeXd9UgWzk/FcyLvJmvjHcW9LWFeK4rZ2f5cXrc8el/aNDwfI+oe6MUnhiE3eNJa7DMpkEtw8ZDlc43XRr1jT+6aGO8CFktuOljoQ3KLXfVjOoaXp3lMgz9yCAsAuhLHcdmMaP7Kkzh8QmfzMTr18XT0aWAKarOlR2G1aLB9ujpgmjs/r64PthLEbjjcQtsbGR8iwMrVIfCaihALf/pr4imAcO1Gqlp5w0SgN3aBGGaI/k2Nc4oVb8Ce/IVkVYVK3TX2ND0wcnWbYw+XNy0UPmAtrPdk9qEBUqNtuiWFr/aZdkGzOxp3JEHOI7cB7pt6zVQuXKyZydUsr1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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