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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id a7sm7618987pfo.32.2021.10.21.21.00.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Oct 2021 21:00:52 -0700 (PDT) Date: Thu, 21 Oct 2021 21:00:51 -0700 From: Kees Cook To: Andrew Morton Cc: Yafang Shao , 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 Message-ID: <202110212053.6F3BB603@keescook> References: <20211021034516.4400-1-laoar.shao@gmail.com> <20211021205222.714a76c854cc0e7a7d6db890@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211021205222.714a76c854cc0e7a7d6db890@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.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 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