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AJvYcCVhZffTE18zeFAKgN2vW9SGCTvoU70G2ELgG4Zbb/VN+CfpsFLnLQS8bTuH+hQ8ssWr8q4Ch4dzWdVEKw9yTkuEyu0= X-Gm-Message-State: AOJu0YyjQt4sqw5uqFIEMsf089r3glE0DMvF4PfKZpZ7tJxunVwnsJVI UYZR0AaA7jjNzLZDs11nT/KUbtJcBgm/Z9mN7stlIOtjPfKdUMRVVyWNNUQuFsaNk1HutcpbTpY mtJaoo9gqqf+WDD0BmT9Y/KtfAX8= X-Google-Smtp-Source: AGHT+IECeNpAbuMBJduU/4vfo0TDc0y586W3/bKZ6gp1RqZAixArBbb8xY+5b1a7GzKTFusgDcdldUI00nJxS7Gmy8k= X-Received: by 2002:a05:690c:6683:b0:61a:c316:9953 with SMTP id 00721157ae682-62fb857416emr57999367b3.11.1718280653503; Thu, 13 Jun 2024 05:10:53 -0700 (PDT) MIME-Version: 1.0 References: <20240613023044.45873-1-laoar.shao@gmail.com> <20240613023044.45873-7-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Thu, 13 Jun 2024 20:10:17 +0800 Message-ID: Subject: Re: [PATCH v2 06/10] mm/kmemleak: Replace strncpy() with __get_task_comm() To: Catalin Marinas Cc: torvalds@linux-foundation.org, ebiederm@xmission.com, alexei.starovoitov@gmail.com, rostedt@goodmis.org, 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, Andrew Morton Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 7059E4000A X-Stat-Signature: 6ersdjjgjcc9caw9mrwzybdjzu1ht7or X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1718280654-587515 X-HE-Meta: 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 NlY73cJP 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 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 Thu, Jun 13, 2024 at 4:37=E2=80=AFPM Catalin Marinas wrote: > > On Thu, Jun 13, 2024 at 10:30:40AM +0800, Yafang Shao wrote: > > Using __get_task_comm() to read the task comm ensures that the name is > > always NUL-terminated, regardless of the source string. This approach a= lso > > facilitates future extensions to the task comm. > > > > Signed-off-by: Yafang Shao > > Cc: Catalin Marinas > > Cc: Andrew Morton > > --- > > mm/kmemleak.c | 8 +------- > > 1 file changed, 1 insertion(+), 7 deletions(-) > > > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > > index d5b6fba44fc9..ef29aaab88a0 100644 > > --- a/mm/kmemleak.c > > +++ b/mm/kmemleak.c > > @@ -663,13 +663,7 @@ static struct kmemleak_object *__alloc_object(gfp_= t gfp) > > strncpy(object->comm, "softirq", sizeof(object->comm)); > > } else { > > object->pid =3D current->pid; > > - /* > > - * There is a small chance of a race with set_task_comm()= , > > - * however using get_task_comm() here may cause locking > > - * dependency issues with current->alloc_lock. In the wor= st > > - * case, the command line is not correct. > > - */ > > - strncpy(object->comm, current->comm, sizeof(object->comm)= ); > > + __get_task_comm(object->comm, sizeof(object->comm), curre= nt); > > } > > You deleted the comment stating why it does not use get_task_comm() > without explaining why it would be safe now. I don't recall the details > but most likely lockdep warned of some potential deadlocks with this > function being called with the task_lock held. > > So, you either show why this is safe or just use strscpy() directly here > (not sure we'd need strscpy_pad(); I think strscpy() would do, we just > need the NUL-termination). The task_lock was dropped in patch #1 [0]. My apologies for not including you in the CC for that change. After this modification, it is now safe to use __get_task_comm(). [0] https://lore.kernel.org/all/20240613023044.45873-2-laoar.shao@gmail.com= / --=20 Regards Yafang