From: Kees Cook <keescook@chromium.org>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: akpm@linux-foundation.org, rostedt@goodmis.org,
mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com,
pmladek@suse.com, peterz@infradead.org, viro@zeniv.linux.org.uk,
valentin.schneider@arm.com, qiang.zhang@windriver.com,
robdclark@chromium.org, christian@brauner.io,
dietmar.eggemann@arm.com, mingo@redhat.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
davem@davemloft.net, kuba@kernel.org, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com,
songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com,
kpsingh@kernel.org, dennis.dalessandro@cornelisnetworks.com,
mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com,
jgg@ziepe.ca, linux-rdma@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, linux-perf-users@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, oliver.sang@intel.com,
lkp@intel.com, Andrii Nakryiko <andrii.nakryiko@gmail.com>
Subject: Re: [PATCH v6 11/12] sched.h: extend task comm from 16 to 24
Date: Mon, 25 Oct 2021 14:30:36 -0700 [thread overview]
Message-ID: <202110251429.DD44ED7B76@keescook> (raw)
In-Reply-To: <20211025083315.4752-12-laoar.shao@gmail.com>
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 <laoar.shao@gmail.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Petr Mladek <pmladek@suse.com>
> ---
> 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.)
>
> extern void scheduler_tick(void);
> --
> 2.17.1
>
--
Kees Cook
next prev parent reply other threads:[~2021-10-25 21:30 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-25 8:33 [PATCH v6 00/12] extend task comm from 16 to 24 Yafang Shao
2021-10-25 8:33 ` [PATCH v6 01/12] fs/exec: make __set_task_comm always set a nul ternimated string Yafang Shao
2021-10-25 21:07 ` Kees Cook
2021-10-26 1:48 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 02/12] fs/exec: make __get_task_comm always get a nul terminated string Yafang Shao
2021-10-25 21:08 ` Kees Cook
2021-10-26 1:49 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 03/12] drivers/connector: make connector comm always nul ternimated Yafang Shao
2021-10-25 21:14 ` Kees Cook
2021-10-26 1:50 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 04/12] drivers/infiniband: make setup_ctxt always get a nul terminated task comm Yafang Shao
2021-10-25 18:20 ` Dennis Dalessandro
2021-10-25 21:16 ` Kees Cook
2021-10-26 1:52 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 05/12] elfcore: make prpsinfo " Yafang Shao
2021-10-25 21:18 ` Kees Cook
2021-10-26 1:56 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 06/12] samples/bpf/test_overhead_kprobe_kern: make it adopt to task comm size change Yafang Shao
2021-10-25 21:20 ` Kees Cook
2021-10-25 8:33 ` [PATCH v6 07/12] samples/bpf/offwaketime_kern: make sched_switch tracepoint args adopt to " Yafang Shao
2021-10-25 21:21 ` Kees Cook
2021-10-26 1:56 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 08/12] tools/bpf/bpftool/skeleton: make it adopt to task " Yafang Shao
2021-10-25 21:24 ` Kees Cook
2021-10-26 2:18 ` Yafang Shao
2021-10-26 13:12 ` Steven Rostedt
2021-10-26 13:55 ` Yafang Shao
2021-10-26 14:02 ` Yafang Shao
2021-10-26 16:09 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 09/12] tools/perf/test: make perf test " Yafang Shao
2021-10-25 21:26 ` Kees Cook
2021-10-25 8:33 ` [PATCH v6 10/12] tools/testing/selftests/bpf: make it " Yafang Shao
2021-10-25 21:29 ` Kees Cook
2021-10-26 2:21 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 11/12] sched.h: extend task comm from 16 to 24 Yafang Shao
2021-10-25 21:30 ` Kees Cook [this message]
2021-10-26 2:22 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 12/12] kernel/kthread: show a warning if kthread's comm is truncated Yafang Shao
2021-10-25 21:35 ` Kees Cook
2021-10-26 2:23 ` Yafang Shao
2021-10-27 20:10 ` Petr Mladek
2021-10-28 1:42 ` Yafang Shao
2021-10-29 7:44 ` Yafang Shao
2021-10-25 18:10 ` [PATCH v6 00/12] extend task comm from 16 to 24 Alexei Starovoitov
2021-10-25 21:05 ` Steven Rostedt
2021-10-25 21:06 ` Kees Cook
2021-10-26 10:35 ` Petr Mladek
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