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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SJJNCBGzUmtsuEprx1i5HjE5RgD2pCrRE+ugyLzOEzM=; b=dyWVSr5etJgXOVjQ3XmJTM5OCCkvqolqIkMmSYlTk4ShcDAkH3iilnF7lIqu9XcRly yMvWWzbZuXQehODcZ601at/mSqkTqJRldut9u/uzGDkVKTgml2emOsk9hn4g557orxag +xiqS+ImFt6IquZr8S6i6EtlKqY8i42E8ss+3etCHdNRkTErgA8v5V/faBwPdPvsMv+W LS1VH7XHGPdG3TvXJopzOxYvqHA43v3PmzqVuSQJ/1wnYlVcX9WKe51DMNQYyEN33x+m vmzfxm9LUTPqnCJuyVuz6uKIhPdJmFCVAObrjkiWzP1F9ZrGxwDBBrJLYFG/I9ind1iY gedg== X-Gm-Message-State: AOAM531zkzZvTcdLz60CIyVgcB0YZto3Gst7i0ZnUGJZwytBJ73pFhLF /FEZ9BQbq+ZpkCh+3xOI5ththLi4Tcd4UwrNSY8= X-Google-Smtp-Source: ABdhPJxLmBzK5FZBxQZCZz83VD8ExfjyjVQb3LuiMJweAWynal5QYJEn08HmmwVm7kPgVnRJmrxLHo7yOYshF0+BFzQ= X-Received: by 2002:a05:6602:2e05:: with SMTP id o5mr12896890iow.204.1635215010620; Mon, 25 Oct 2021 19:23:30 -0700 (PDT) MIME-Version: 1.0 References: <20211025083315.4752-1-laoar.shao@gmail.com> <20211025083315.4752-12-laoar.shao@gmail.com> <202110251429.DD44ED7B76@keescook> In-Reply-To: <202110251429.DD44ED7B76@keescook> From: Yafang Shao Date: Tue, 26 Oct 2021 10:22:54 +0800 Message-ID: Subject: Re: [PATCH v6 11/12] sched.h: extend task comm from 16 to 24 To: Kees Cook Cc: Andrew Morton , Steven Rostedt , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Petr Mladek , Peter Zijlstra , Al Viro , Valentin Schneider , Qiang Zhang , robdclark , christian , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Vincent Guittot , David Miller , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin Lau , Song Liu , Yonghong Song , john fastabend , KP Singh , dennis.dalessandro@cornelisnetworks.com, mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com, jgg@ziepe.ca, linux-rdma@vger.kernel.org, netdev , bpf , "linux-perf-use." , linux-fsdevel@vger.kernel.org, Linux MM , LKML , kernel test robot , kbuild test robot , Andrii Nakryiko Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 2868D1908 Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=WTtEtNem; spf=pass (imf22.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.166.43 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: saj7ikddi6chithyktwbgc4yi839gc76 X-Rspamd-Server: rspam06 X-HE-Tag: 1635215011-609819 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: On Tue, Oct 26, 2021 at 5:30 AM Kees Cook wrote: > > On Mon, Oct 25, 2021 at 08:33:14AM +0000, Yafang Shao wrote: > > When I was implementing a new per-cpu kthread cfs_migration, I found the > > comm of it "cfs_migration/%u" is truncated due to the limitation of > > TASK_COMM_LEN. For example, the comm of the percpu thread on CPU10~19 are > > all with the same name "cfs_migration/1", which will confuse the user. This > > issue is not critical, because we can get the corresponding CPU from the > > task's Cpus_allowed. But for kthreads correspoinding to other hardware > > devices, it is not easy to get the detailed device info from task comm, > > for example, > > > > jbd2/nvme0n1p2- > > xfs-reclaim/sdf > > > > We can also shorten the name to work around this problem, but I find > > there are so many truncated kthreads: > > > > rcu_tasks_kthre > > rcu_tasks_rude_ > > rcu_tasks_trace > > poll_mpt3sas0_s > > ext4-rsv-conver > > xfs-reclaim/sd{a, b, c, ...} > > xfs-blockgc/sd{a, b, c, ...} > > xfs-inodegc/sd{a, b, c, ...} > > audit_send_repl > > ecryptfs-kthrea > > vfio-irqfd-clea > > jbd2/nvme0n1p2- > > ... > > > > We should improve this problem fundamentally by extending comm size to > > 24 bytes. task_struct is growing rather regularly by 8 bytes. > > > > After this change, the truncated kthreads listed above will be > > displayed as: > > > > rcu_tasks_kthread > > rcu_tasks_rude_kthread > > rcu_tasks_trace_kthread > > poll_mpt3sas0_statu > > ext4-rsv-conversion > > xfs-reclaim/sdf1 > > xfs-blockgc/sdf1 > > xfs-inodegc/sdf1 > > audit_send_reply > > ecryptfs-kthread > > vfio-irqfd-cleanup > > jbd2/nvme0n1p2-8 > > > > As we have converted all the unsafe copy of task comm to the safe one, > > this change won't make any trouble to the kernel or the in-tree tools. > > The safe one and unsafe one of comm copy as follows, > > > > Unsafe Safe > > strlcpy strscpy_pad > > strncpy strscpy_pad > > bpf_probe_read_kernel bpf_probe_read_kernel_str > > bpf_core_read_str > > bpf_get_current_comm > > perf_event__prepare_comm > > prctl(2) > > > > Regarding the possible risk it may take to the out-of-tree user tools, if > > the user tools get the task comm through kernel API like prctl(2), > > bpf_get_current_comm() and etc, the tools still work well after this > > change. While If the user tools get the task comm through direct string > > copy, it must make sure the copied string should be with a nul terminator. > > > > Signed-off-by: Yafang Shao > > Cc: Mathieu Desnoyers > > Cc: Arnaldo Carvalho de Melo > > Cc: Andrii Nakryiko > > Cc: Peter Zijlstra > > Cc: Steven Rostedt > > Cc: Al Viro > > Cc: Kees Cook > > Cc: Petr Mladek > > --- > > include/linux/sched.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index 124538db792c..490d12eabe44 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -279,7 +279,7 @@ struct task_group; > > * BPF programs. > > */ > > enum { > > - TASK_COMM_LEN = 16, > > + TASK_COMM_LEN = 24, > > }; > > I suspect this should be kept in sync with the tools/ copy of sched.h > (i.e. we may need to keep the TASK_COMM_LEN_16 around in the kernel tree > too.) > Sure. I will change it. > > > > extern void scheduler_tick(void); > > -- > > 2.17.1 > > > > -- > Kees Cook -- Thanks Yafang