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AJvYcCUCJU09e6x/kRknjJnrRxsQZsUxgIoOUNAKkO7/Lz4Of7YnVfHe1R7jizn8Ug+qkGbMDDA0YakOvA==@kvack.org X-Gm-Message-State: AOJu0Yxkt0k1CIJUBNJ6zMbrZ7gnoXAWNfDTIrM8vEdZrySh1FunvoWc 0FD19RyeG+68RDBmBJP6UnMJS4j+uCu3T4zX5XI49F6QCEogNK4y4fhyDc64ZpXV5CROiLBSob0 ObLc0q5RgbMhSDeqFxMTUhrXhQ8Lj21o= X-Gm-Gg: ASbGncui0OaapyO28j2aHEVT6+lIpTbjSuMZuPN19qACgUSra1t6hVvwRu3dY9H/hhi mZp9CTMZeTIdkJm6+PWHlu5+xl139VAxO6l48YoedF9hcnvExUuQ6SC7vxekEYSDOGzuSjuzPlK NUHYCGOxwYo1YbmPbPpnsUGFD/fkwJxChEhagzew8GG1O6 X-Google-Smtp-Source: AGHT+IEbl6ReOpb49RwwL8AZJ/9Sol4SvQN4M0UGm1K51odVAmk0xoRFec0CSuR4PFQ6HC9MD2pnvl3mwXOmXHsstbQ= X-Received: by 2002:a05:622a:1e8b:b0:48d:66ee:662a with SMTP id d75a77b69052e-494ae58b769mr436574031cf.26.1747895289152; Wed, 21 May 2025 23:28:09 -0700 (PDT) MIME-Version: 1.0 References: <20250521062337.53262-1-bhupesh@igalia.com> <20250521062337.53262-3-bhupesh@igalia.com> In-Reply-To: From: Yafang Shao Date: Thu, 22 May 2025 14:27:33 +0800 X-Gm-Features: AX0GCFsGdF0c_dPvPXc154mXKd8pL9O5JIppXmD9XtCHG7b0h4OOt3XBeUQIsTU Message-ID: Subject: Re: [PATCH v4 2/3] treewide: Switch memcpy() users of 'task->comm' to a more safer implementation To: Bhupesh Cc: akpm@linux-foundation.org, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, keescook@chromium.org, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-trace-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1AF0CC000B X-Stat-Signature: sq9uyfm6epod5yhanzpk64ir8khq9f5z X-Rspam-User: X-HE-Tag: 1747895289-932467 X-HE-Meta: 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 cmUupypu 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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, May 22, 2025 at 2:15=E2=80=AFPM Yafang Shao = wrote: > > On Wed, May 21, 2025 at 2:24=E2=80=AFPM Bhupesh wrot= e: > > > > As Linus mentioned in [1], currently we have several memcpy() use-cases > > which use 'current->comm' to copy the task name over to local copies. > > For an example: > > > > ... > > char comm[TASK_COMM_LEN]; > > memcpy(comm, current->comm, TASK_COMM_LEN); > > ... > > > > These should be modified so that we can later implement approaches > > to handle the task->comm's 16-byte length limitation (TASK_COMM_LEN) > > is a more modular way (follow-up patches do the same): > > > > ... > > char comm[TASK_COMM_LEN]; > > memcpy(comm, current->comm, TASK_COMM_LEN); > > comm[TASK_COMM_LEN - 1] =3D '\0'; > > ... > > > > The relevant 'memcpy()' users were identified using the following searc= h > > pattern: > > $ git grep 'memcpy.*->comm\>' > > Hello Bhupesh, > > Several BPF programs currently read task->comm directly, as seen in: > > // tools/testing/selftests/bpf/progs/test_skb_helpers.c [0] > bpf_probe_read_kernel_str(&comm, sizeof(comm), &task->comm); > > This approach may cause issues after the follow-up patch. > I believe we should replace it with the safer bpf_get_current_comm() > or explicitly null-terminate it with "comm[sizeof(comm) - 1] =3D '\0'". > Out-of-tree BPF programs like BCC[1] or bpftrace[2] relying on direct > task->comm access may also break and require updates. > > [0]. https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tre= e/tools/testing/selftests/bpf/progs/test_skb_helpers.c#n26 > [1]. https://github.com/iovisor/bcc > [2]. https://github.com/bpftrace/bpftrace Hmm, upon checking, I confirmed that bpf_probe_read_kernel_str() already ensures the destination string is null-terminated. Therefore, this change is unnecessary. Please disregard my previous comment. --=20 Regards Yafang