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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=ScHBEadlhvXJ5Ux51PKGxkHvsss0u6ctZT9nDJJQkzo=; b=EGk7/2sDzyZKhqzNWBhdryG3JL+XkAEQPiAfBIuDE9R6RLt2nfRAWAw3jH0JhDP+9g 8qWrFdFKDQFEkHfLR7ESlJPvhqaeOJWUyE+yZZ9WLzLhKaIh0Dr1fFdvUyR8FcxUQXPI wt1wCmUyJCNEfsh8+Lw9J7bNk6tvzL5kfFRZ9ZWE2dqio66PYnYJVP6Vyf6Qrptw0q9G L3jzCGvV2A4SEqRX0/MXV2wRM3jToF3Ck/aAvUUG11B1ll2SrlTdIBa6XB6sRkvp9g9h 69uOd/l98sXS4A10jUYB73Iqg3+deXZIqB9z6u+5DbvOxyHJcjar51OUXXG2nGpeaFzU 9kUQ== X-Gm-Message-State: AOAM531HX2SfYLvobYkizTAwsursfnMhkdPR+Qiulf9f2Whw/D/VXZeV lXgTWK9XF5ydMJcjm9wn4+YRwx0nDemIDY5+zEg= X-Google-Smtp-Source: ABdhPJweqQlORvX/kcER+dfOkqBBAlDqGVNYLVFUw0Z1O7FC8HmC4bC+PzzQe5iYslImeJRoEVpzyLvNvGA91aU5hCs= X-Received: by 2002:a05:6602:2e05:: with SMTP id o5mr12805350iow.204.1635213004755; Mon, 25 Oct 2021 18:50:04 -0700 (PDT) MIME-Version: 1.0 References: <20211025083315.4752-1-laoar.shao@gmail.com> <20211025083315.4752-3-laoar.shao@gmail.com> <202110251408.2E661E70BC@keescook> In-Reply-To: <202110251408.2E661E70BC@keescook> From: Yafang Shao Date: Tue, 26 Oct 2021 09:49:28 +0800 Message-ID: Subject: Re: [PATCH v6 02/12] fs/exec: make __get_task_comm always get a nul terminated string 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 Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 56A669000253 X-Stat-Signature: 14mzubtf378jwfsoiy1aiydrxtjww1tz Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=Fx3ncUFZ; spf=pass (imf29.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.166.53 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-HE-Tag: 1635213005-454506 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 5:08 AM Kees Cook wrote: > > On Mon, Oct 25, 2021 at 08:33:05AM +0000, Yafang Shao wrote: > > If the dest buffer size is smaller than sizeof(tsk->comm), the buffer > > will be without null ternimator, that may cause problem. We can make sure > > the buffer size not smaller than comm at the callsite to avoid that > > problem, but there may be callsite that we can't easily change. > > > > Using strscpy_pad() instead of strncpy() in __get_task_comm() can make > > the string always nul ternimated. > > > > Suggested-by: Kees Cook > > Suggested-by: Steven Rostedt > > Signed-off-by: Yafang Shao > > Cc: Mathieu Desnoyers > > Cc: Arnaldo Carvalho de Melo > > Cc: Andrii Nakryiko > > Cc: Peter Zijlstra > > Cc: Steven Rostedt > > Cc: Al Viro > > Cc: Kees Cook > > Cc: Petr Mladek > > --- > > fs/exec.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/fs/exec.c b/fs/exec.c > > index 404156b5b314..bf2a7a91eeea 100644 > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1209,7 +1209,8 @@ static int unshare_sighand(struct task_struct *me) > > char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) > > { > > task_lock(tsk); > > - strncpy(buf, tsk->comm, buf_size); > > + /* The copied value is always null terminated */ > > This may could say "always NUL terminated and zero-padded" > Sure. I will change it. > > + strscpy_pad(buf, tsk->comm, buf_size); > > task_unlock(tsk); > > return buf; > > } > > -- > > 2.17.1 > > > > But for the replacement with strscpy_pad(), yes please: > > Reviewed-by: Kees Cook > > > -- > Kees Cook -- Thanks Yafang