Messages in this thread | | | Date | Thu, 7 Oct 2021 07:56:57 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v2 3/4] sched.h: extend task comm from 16 to 24 for CONFIG_BASE_FULL |
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On Thu, Oct 07, 2021 at 12:07:51PM +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- > nvidia-modeset/ > > 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- > ... > > Besides the in-tree kthreads listed above, the out-of-tree kthreads may > also be truncated: > > rtase_work_queu > nvidia-modeset/ > UVM global queu > UVM deferred re > ... > > We should improve this problem fundamentally. > > This patch extends the size of task comm to 24 bytes, which is the > same length with workqueue's, for the CONFIG_BASE_FULL case. And for the > CONFIG_BASE_SMALL case, the size of task comm is still kept as 16 bytes. > > Suggested-by: Petr Mladek <pmladek@suse.com> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
This, as expected, adds 8 bytes to task_struct, which is reasonable. I don't see any easy places to consolidate other members to make this a "free" change, but I did just remove 64 bytes from task_struct[1], so this is okay. :)
Reviewed-by: Kees Cook <keescook@chromium.org>
[1] https://lore.kernel.org/lkml/20210924025450.4138503-1-keescook@chromium.org/
-- Kees Cook
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