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Biederman" To: Tycho Andersen Cc: Aleksa Sarai , Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Jeff Layton , Chuck Lever , Alexander Aring , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tycho Andersen , Zbigniew =?utf-8?Q?J=C4=99drzejewski-Szmek?= References: <20240924141001.116584-1-tycho@tycho.pizza> <87msjx9ciw.fsf@email.froward.int.ebiederm.org> <20240925.152228-private.conflict.frozen.trios-TdUGhuI5Sb4v@cyphar.com> <878qvf17zl.fsf@email.froward.int.ebiederm.org> Date: Fri, 27 Sep 2024 09:43:22 -0500 In-Reply-To: (Tycho Andersen's message of "Fri, 27 Sep 2024 08:07:20 -0600") Message-ID: <87h6a1xilx.fsf@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1suCBt-009qW1-G2;;;mid=<87h6a1xilx.fsf@email.froward.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.165.127;;;frm=ebiederm@xmission.com;;;spf=pass X-XM-AID: U2FsdGVkX19odIX+pzGkJDzocY816Air47iY1grMlMY= Subject: Re: [RFC] exec: add a flag for "reasonable" execveat() comm X-SA-Exim-Connect-IP: 166.70.13.51 X-SA-Exim-Rcpt-To: zbyszek@in.waw.pl, tandersen@netflix.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, alex.aring@gmail.com, chuck.lever@oracle.com, jlayton@kernel.org, kees@kernel.org, jack@suse.cz, brauner@kernel.org, viro@zeniv.linux.org.uk, cyphar@cyphar.com, tycho@tycho.pizza X-SA-Exim-Mail-From: ebiederm@xmission.com X-SA-Exim-Scanned: No (on out03.mta.xmission.com); SAEximRunCond expanded to false X-Rspam-User: X-Rspamd-Queue-Id: 70FC340006 X-Rspamd-Server: rspam01 X-Stat-Signature: jx3spcn3fiabtf6hw5nt96pgdwoz85zg X-HE-Tag: 1727448213-867447 X-HE-Meta: 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 OzLGh8hJ qOWdPvUljnQVwzsr09RqSVFI60A2Mt58hXIcR1VQLL2cBdwEwmgjgE4C7NlIVstfL5t4pkrR//t0W2dqP8Tz+nqA4CQ== 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: List-Subscribe: List-Unsubscribe: Tycho Andersen writes: > On Wed, Sep 25, 2024 at 09:09:18PM -0500, Eric W. Biederman wrote: >> Tycho Andersen writes: >> >> > Yep, I did this for the test above, and it worked fine: >> > >> > if (bprm->fdpath) { >> > /* >> > * If fdpath was set, execveat() made up a path that will >> > * probably not be useful to admins running ps or similar. >> > * Let's fix it up to be something reasonable. >> > */ >> > struct path root; >> > char *path, buf[1024]; >> > >> > get_fs_root(current->fs, &root); >> > path = __d_path(&bprm->file->f_path, &root, buf, sizeof(buf)); >> > >> > __set_task_comm(me, kbasename(path), true); >> > } else { >> > __set_task_comm(me, kbasename(bprm->filename), true); >> > } >> > >> > obviously we don't want a stack allocated buffer, but triggering on >> > ->fdpath != NULL seems like the right thing, so we won't need a flag >> > either. >> > >> > The question is: argv[0] or __d_path()? >> >> You know. I think we can just do: >> >> BUILD_BUG_ON(DNAME_INLINE_LEN >= TASK_COMM_LEN); >> __set_task_comm(me, bprm->file->f_path.dentry->d_name.name, true); >> >> Barring cache misses that should be faster and more reliable than what >> we currently have and produce the same output in all of the cases we >> like, and produce better output in all of the cases that are a problem >> today. >> >> Does anyone see any problem with that? > > Nice, this works great. We need to drop the BUILD_BUG_ON() since it is > violated in today's tree, but I think this is safe to do anyway since > __set_task_comm() does strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)). Doh. I simply put the conditional in the wrong order. That should have been: BUILD_BUG_ON(TASK_COMM_LEN > DNAME_INLINE_LEN); Sorry I was thinking of the invariant that needs to be preserved rather than the bug that happens. Eric