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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=M+TEaQB1KaSOudASCPt2E3PS4ymJyoJAqUYafZ8gI7E=; b=LDtc9K4dORYWkk5EUYUcgL6so0U3faPdldTQJn6cz3IV5WWYXpjdgyrXiZ4O5xmFnT vwf+X+zenhd09wId8K/3zlAsnN3Bk0RisxyqyCG82PcPHT/MXibvsdAgL9M2LLdEsL8W k2Jty4nswumRAJUKZbrxps7p32YSdCb39ML7eSDHtQrrHBKkBj/b3wDb5/bSdDgsz0nt M4atjd1YZWEjOsOmmg5F+g4nD4h82onCkCcr8p1OeyoQ3rKSh2SbW2gS477dw8v06Fag L8RL7yxW7U6OoJVD0doNNnWPx92+rL8MEgTWeK3RNIDSJDn0s6GBEcthycYs/d4z7SPb iGDg== X-Gm-Message-State: AOAM530Dx/Vlz+CwRMgdVvU274DcfMl1o0I+tx/FTrlMMGceSX+CHT9S +doA6Y4J1zzWXAa80rJkF0u04+D/K9n/8j5NKnI= X-Google-Smtp-Source: ABdhPJzo8Pl2UbPecXV9ZclgT3FzrihDFm7Isxsh4OePzHurnJ+maCBZCvaVaerHAt6wvuSmpFvZzPlkXSA+3EMqRwA= X-Received: by 2002:a5d:9493:: with SMTP id v19mr13031702ioj.34.1635213079114; Mon, 25 Oct 2021 18:51:19 -0700 (PDT) MIME-Version: 1.0 References: <20211025083315.4752-1-laoar.shao@gmail.com> <20211025083315.4752-4-laoar.shao@gmail.com> <202110251411.93B477676B@keescook> In-Reply-To: <202110251411.93B477676B@keescook> From: Yafang Shao Date: Tue, 26 Oct 2021 09:50:43 +0800 Message-ID: Subject: Re: [PATCH v6 03/12] drivers/connector: make connector comm always nul ternimated 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 , Vladimir Zapolskiy , David Howells Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B15631900 X-Stat-Signature: yygmniq5uzzoh5pcjsrso16qw1hwybom Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=oL8HHOww; spf=pass (imf22.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.166.49 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-HE-Tag: 1635213079-832113 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 5:14 AM Kees Cook wrote: > > On Mon, Oct 25, 2021 at 08:33:06AM +0000, Yafang Shao wrote: > > connector comm was introduced in commit > > f786ecba4158 ("connector: add comm change event report to proc connector"). > > struct comm_proc_event was defined in include/linux/cn_proc.h first and > > then been moved into file include/uapi/linux/cn_proc.h in commit > > 607ca46e97a1 ("UAPI: (Scripted) Disintegrate include/linux"). > > > > As this is the UAPI code, we can't change it without potentially breaking > > things (i.e. userspace binaries have this size built in, so we can't just > > change the size). To prepare for the followup change - extending task > > comm, we have to use __get_task_comm() to avoid the BUILD_BUG_ON() in > > proc_comm_connector(). > > I wonder, looking at this again, if it might make more sense to avoid > this cn_proc.c change, and instead, adjust get_task_comm() like so: > > #define get_task_comm(buf, tsk) > __get_task_comm(buf, __must_be_array(buf) + sizeof(buf), tsk) > > This would still enforce the original goal of making sure > get_task_comm() is being used on a char array, and now that > __get_task_comm() will truncate & pad, it's safe to use on both > too-small and too-big arrays. > It Makes sense to me. I will do it as you suggested. -- Thanks Yafang