From patchwork Sun Mar 8 21:36:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 11425847 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2FD7614B7 for ; Sun, 8 Mar 2020 21:38:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ECD642084E for ; Sun, 8 Mar 2020 21:38:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ECD642084E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 308F56B0003; Sun, 8 Mar 2020 17:38:39 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 2B8E66B0007; Sun, 8 Mar 2020 17:38:39 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1CF736B0008; Sun, 8 Mar 2020 17:38:39 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0002.hostedemail.com [216.40.44.2]) by kanga.kvack.org (Postfix) with ESMTP id 055196B0003 for ; Sun, 8 Mar 2020 17:38:39 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id F3BEA180AD807 for ; Sun, 8 Mar 2020 21:38:38 +0000 (UTC) X-FDA: 76573509516.04.tent26_4b6ce6e40e840 X-Spam-Summary: 2,0,0,f664f632ce56db74,d41d8cd98f00b204,ebiederm@xmission.com,,RULES_HIT:41:69:355:379:800:960:973:988:989:1260:1277:1313:1314:1345:1359:1437:1516:1518:1535:1542:1711:1730:1747:1777:1792:2393:2553:2559:2562:2895:3138:3139:3140:3141:3142:3353:3865:3867:3868:3870:3871:3872:3874:4119:4321:5007:6261:6625:6691:6742:6743:9592:10004:10400:11026:11232:11658:11914:12043:12291:12296:12297:12438:12517:12519:12555:12683:12895:13255:14096:14097:14110:14181:14394:14721:21080:21212:21324:21451:21627:21990:30012:30054:30055:30070:30090,0,RBL:166.70.13.232:@xmission.com:.lbl8.mailshell.net-62.18.0.100 66.100.201.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:23,LUA_SUMMARY:none X-HE-Tag: tent26_4b6ce6e40e840 X-Filterd-Recvd-Size: 8047 Received: from out02.mta.xmission.com (out02.mta.xmission.com [166.70.13.232]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Sun, 8 Mar 2020 21:38:38 +0000 (UTC) Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jB3d4-0007cP-VM; Sun, 08 Mar 2020 15:38:35 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jB3d3-0001ox-Uq; Sun, 08 Mar 2020 15:38:34 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Bernd Edlinger Cc: Christian Brauner , Kees Cook , Jann Horn , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , Thomas Gleixner , Oleg Nesterov , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra \(Intel\)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc\@vger.kernel.org" , "linux-kernel\@vger.kernel.org" , "linux-fsdevel\@vger.kernel.org" , "linux-mm\@kvack.org" , "stable\@vger.kernel.org" , "linux-api\@vger.kernel.org" References: <87k142lpfz.fsf@x220.int.ebiederm.org> <875zfmloir.fsf@x220.int.ebiederm.org> <87v9nmjulm.fsf@x220.int.ebiederm.org> <202003021531.C77EF10@keescook> <20200303085802.eqn6jbhwxtmz4j2x@wittgenstein> <87v9nlii0b.fsf@x220.int.ebiederm.org> <87a74xi4kz.fsf@x220.int.ebiederm.org> <87r1y8dqqz.fsf@x220.int.ebiederm.org> <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> Date: Sun, 08 Mar 2020 16:36:17 -0500 In-Reply-To: <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Sun, 08 Mar 2020 16:34:37 -0500") Message-ID: <87k13u5y26.fsf_-_@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1jB3d3-0001ox-Uq;;;mid=<87k13u5y26.fsf_-_@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX181hWQFhcXeH2DZ7lmXnC5JxL6rk00Uo9s= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa06.xmission.com X-Spam-Level: X-Spam-Status: No, score=0.5 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,T_TooManySym_01,XMSubLong autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4999] * 0.7 XMSubLong Long Subject * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Bernd Edlinger X-Spam-Relay-Country: X-Spam-Timing: total 592 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 3.0 (0.5%), b_tie_ro: 2.1 (0.3%), parse: 1.46 (0.2%), extract_message_metadata: 13 (2.2%), get_uri_detail_list: 1.98 (0.3%), tests_pri_-1000: 17 (2.8%), tests_pri_-950: 1.24 (0.2%), tests_pri_-900: 1.07 (0.2%), tests_pri_-90: 31 (5.2%), check_bayes: 30 (5.0%), b_tokenize: 12 (2.0%), b_tok_get_all: 9 (1.6%), b_comp_prob: 2.2 (0.4%), b_tok_touch_all: 4.0 (0.7%), b_finish: 0.61 (0.1%), tests_pri_0: 514 (86.8%), check_dkim_signature: 0.57 (0.1%), check_dkim_adsp: 2.6 (0.4%), poll_dns_idle: 1.00 (0.2%), tests_pri_10: 2.1 (0.4%), tests_pri_500: 6 (1.0%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH v2 2/5] exec: Factor unshare_sighand out of de_thread and call it separately X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) 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: This makes the code clearer and makes it easier to implement a mutex that is not taken over any locations that may block indefinitely waiting for userspace. Signed-off-by: "Eric W. Biederman" Reviewed-by: Bernd Edlinger Reviewed-by: Kees Cook Acked-by: Christian Brauner --- fs/exec.c | 39 ++++++++++++++++++++++++++------------- 1 file changed, 26 insertions(+), 13 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index c3f34791f2f0..ff74b9a74d34 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1194,6 +1194,23 @@ static int de_thread(struct task_struct *tsk) flush_itimer_signals(); #endif + BUG_ON(!thread_group_leader(tsk)); + return 0; + +killed: + /* protects against exit_notify() and __exit_signal() */ + read_lock(&tasklist_lock); + sig->group_exit_task = NULL; + sig->notify_count = 0; + read_unlock(&tasklist_lock); + return -EAGAIN; +} + + +static int unshare_sighand(struct task_struct *me) +{ + struct sighand_struct *oldsighand = me->sighand; + if (refcount_read(&oldsighand->count) != 1) { struct sighand_struct *newsighand; /* @@ -1210,23 +1227,13 @@ static int de_thread(struct task_struct *tsk) write_lock_irq(&tasklist_lock); spin_lock(&oldsighand->siglock); - rcu_assign_pointer(tsk->sighand, newsighand); + rcu_assign_pointer(me->sighand, newsighand); spin_unlock(&oldsighand->siglock); write_unlock_irq(&tasklist_lock); __cleanup_sighand(oldsighand); } - - BUG_ON(!thread_group_leader(tsk)); return 0; - -killed: - /* protects against exit_notify() and __exit_signal() */ - read_lock(&tasklist_lock); - sig->group_exit_task = NULL; - sig->notify_count = 0; - read_unlock(&tasklist_lock); - return -EAGAIN; } char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) @@ -1264,13 +1271,19 @@ int flush_old_exec(struct linux_binprm * bprm) int retval; /* - * Make sure we have a private signal table and that - * we are unassociated from the previous thread group. + * Make this the only thread in the thread group. */ retval = de_thread(me); if (retval) goto out; + /* + * Make the signal table private. + */ + retval = unshare_sighand(me); + if (retval) + goto out; + /* * Must be called _before_ exec_mmap() as bprm->mm is * not visibile until then. This also enables the update