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From: Kees Cook <keescook@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Yafang Shao <laoar.shao@gmail.com>,
	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, netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, oliver.sang@intel.com,
	lkp@intel.com
Subject: Re: [PATCH v5 00/15] extend task comm from 16 to 24 for CONFIG_BASE_FULL
Date: Thu, 21 Oct 2021 21:00:51 -0700	[thread overview]
Message-ID: <202110212053.6F3BB603@keescook> (raw)
In-Reply-To: <20211021205222.714a76c854cc0e7a7d6db890@linux-foundation.org>

On Thu, Oct 21, 2021 at 08:52:22PM -0700, Andrew Morton wrote:
> On Thu, 21 Oct 2021 03:45:07 +0000 Yafang Shao <laoar.shao@gmail.com> wrote:
> 
> > This patchset changes files among many subsystems. I don't know which
> > tree it should be applied to, so I just base it on Linus's tree.
> 
> I can do that ;)
> 
> > There're many truncated kthreads in the kernel, which may make trouble
> > for the user, for example, the user can't get detailed device
> > information from the task comm.
> 
> That sucked of us.
> 
> > This patchset tries to improve this problem fundamentally by extending
> > the task comm size from 16 to 24. In order to do that, we have to do
> > some cleanups first.
> 
> It's at v5 and there's no evidence of review activity?  C'mon, folks!

It's on my list! :) It's a pretty subtle area that rarely changes, so I
want to make sure I'm a full coffee to do the review. :)

> > 1. Make the copy of task comm always safe no matter what the task
> > comm size is. For example,
> > 
> >   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)
> > 
> > 2. Replace the old hard-coded 16 with a new macro TASK_COMM_LEN_16 to
> > make it more grepable.
> > 
> > 3. Extend the task comm size to 24 for CONFIG_BASE_FULL case and keep it
> > as 16 for CONFIG_BASE_SMALL.
> 
> Is this justified?  How much simpler/more reliable/more maintainable/
> would the code be if we were to make CONFIG_BASE_SMALL suffer with the
> extra 8 bytes?

Does anyone "own" CONFIG_BASE_SMALL? Gonna go with "no":

$ git ann init/Kconfig| grep 'config BASE_SMALL'
1da177e4c3f41   (Linus Torvalds 2005-04-16 15:20:36 -0700 2054)config BASE_SMALL

And it looks mostly unused:

$ git grep CONFIG_BASE_SMALL | cut -d: -f1 | sort -u | xargs -n1 git ann -f | grep 'CONFIG_BASE_SMALL'
b2af018ff26f1   (Ingo Molnar    2009-01-28 17:36:56 +0100       18)#if CONFIG_BASE_SMALL == 0
fcdba07ee390d   ( Jiri Olsa     2011-02-07 19:31:25 +0100       54)#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
Blaming lines: 100% (46/46), done.
1da177e4c3f41   (Linus Torvalds 2005-04-16 15:20:36 -0700       28)#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000)
1da177e4c3f41   (Linus Torvalds 2005-04-16 15:20:36 -0700       34)#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
Blaming lines: 100% (162/162), done.
f86dcc5aa8c79   (Eric Dumazet   2009-10-07 00:37:59 +0000       31)#define UDP_HTABLE_SIZE_MIN     (CONFIG_BASE_SMALL ? 128 : 256)
02c02bf12c5d8   (Matthew Wilcox 2017-11-03 23:09:45 -0400       1110)#define XA_CHUNK_SHIFT        (CONFIG_BASE_SMALL ? 4 : 6)
a52b89ebb6d44   (Davidlohr Bueso        2014-01-12 15:31:23 -0800       4249)#if CONFIG_BASE_SMALL
7b44ab978b77a   (Eric W. Biederman      2011-11-16 23:20:58 -0800       78)#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)


-- 
Kees Cook

  reply	other threads:[~2021-10-22  4:01 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-21  3:45 [PATCH v5 00/15] extend task comm from 16 to 24 for CONFIG_BASE_FULL Yafang Shao
2021-10-21  3:45 ` [PATCH v5 01/15] fs/exec: make __set_task_comm always set a nul ternimated string Yafang Shao
2021-10-21  3:45 ` [PATCH v5 02/15] fs/exec: make __get_task_comm always get a nul terminated string Yafang Shao
2021-10-21  3:45 ` [PATCH v5 03/15] sched.h: introduce TASK_COMM_LEN_16 Yafang Shao
2021-10-21 21:55   ` Andrii Nakryiko
2021-10-22  6:23     ` Yafang Shao
2021-10-21  3:45 ` [PATCH v5 04/15] cn_proc: make connector comm always nul ternimated Yafang Shao
2021-10-21  3:45 ` [PATCH v5 05/15] drivers/infiniband: make setup_ctxt always get a nul terminated task comm Yafang Shao
2021-10-21  3:45 ` [PATCH v5 06/15] elfcore: make prpsinfo " Yafang Shao
2021-10-21  3:45 ` [PATCH v5 07/15] samples/bpf/kern: use TASK_COMM_LEN instead of hard-coded 16 Yafang Shao
2021-10-21  3:45 ` [PATCH v5 08/15] samples/bpf/user: use TASK_COMM_LEN_16 " Yafang Shao
2021-10-21  3:45 ` [PATCH v5 09/15] tools/include: introduce TASK_COMM_LEN_16 Yafang Shao
2021-10-22  3:52 ` [PATCH v5 00/15] extend task comm from 16 to 24 for CONFIG_BASE_FULL Andrew Morton
2021-10-22  4:00   ` Kees Cook [this message]
2021-10-22  6:20     ` Yafang Shao

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