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x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=microsoft.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935920AbeCSVrR (ORCPT ); Mon, 19 Mar 2018 17:47:17 -0400 Received: from mail-co1nam03on0137.outbound.protection.outlook.com ([104.47.40.137]:6596 "EHLO NAM03-CO1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934753AbeCSP6S (ORCPT ); Mon, 19 Mar 2018 11:58:18 -0400 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Kirill Tkhai , Andrei Vagin , Andreas Gruenbacher , Kees Cook , Michael Kerrisk , Al Viro , Oleg Nesterov , Paul Moore , Eric Biederman , Andy Lutomirski , Ingo Molnar , Serge Hallyn , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 022/281] pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid() Thread-Topic: [PATCH AUTOSEL for 4.9 022/281] pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid() Thread-Index: AQHTv5sYD4JpEQ98XUeYudaOqrB6Qw== Date: Mon, 19 Mar 2018 15:58:16 +0000 Message-ID: <20180319155742.13731-22-alexander.levin@microsoft.com> References: <20180319155742.13731-1-alexander.levin@microsoft.com> In-Reply-To: <20180319155742.13731-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;DM5PR2101MB0933;7:ohK8rp2MgAnMjrsEiSQg+UjQpQru2jR1DFIc24hVZYTL6hUIONJLQtqbQ/wNu4gWWSbA2rd+FErYWnJvA7AYMbZ045GmXVpr5/i+Ts15Iz5Rp2QQ8Tg6GeCIWTfcXTngy5ZTpmMqno7q6tCzsZzUV3XQywK5d1po8eDWr0Z6UWu7DMyq0FNA1kaGg3IyCP33dp2bhT6+3hp9hZxoVEb+mWspeqewXOapdmYQiVisgd7OBxil24eDeIRbPrBM628v;20:QeUfAO9G0quzgfhJ1Gcvt3HXUnIgmR5lpO1IHqxsn9ivmM9qP0+WJirz2rhvjX/YW3P5/pKPuBLvLLLmk83B9NjqrBoggM0v5VBXWlgNx9lcquwC4/Q4G+WAWYBPaIdUB07EgxiN/luDoG9nBFkjocH1XEiM1bdr9TVgc+6NFnQ= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 96f3e8b6-8894-4b95-2ec8-08d58db23aaa x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB0933; 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authentication-results: spf=none (sender IP is ) smtp.mailfrom=Alexander.Levin@microsoft.com; x-microsoft-antispam-message-info: O+1K180klbXWzDBtDZ9ApYIMcjGvbWHRc10fQCcFCD2KrxN5pZ4hbtSq31ah2p4S2VwEgXWft3ylMaPpx7RfnmMgAGbgQW01dCwW52RmnYAerLdb5xUN7VDaZNhgqBhvMclkaDOJNVAKeItLHd0SRUYkBnLzRQmi0+i5+sWb4I74rWLPiyJvu2nuNGrGkgXL5io83S1usrVXsfmr+Zym2fXxcCjg30FbKjc0me1L/mj0ZjLzK+3v8EfgTVZCXag2carXfdpLi2AlT7waYbJFdXZhs9+cGJwrwLdDyWiUgvToMFDiO7PBMvIOMOboZ5bYPKlgVOdXKxACG9CeI2ly/A== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 96f3e8b6-8894-4b95-2ec8-08d58db23aaa X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 15:58:16.9599 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB0933 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Kirill Tkhai [ Upstream commit 8896c23d2ef803f1883fea73117a435925c2b4c4 ] alloc_pidmap() advances pid_namespace::last_pid. When first pid allocation fails, then next created process will have pid 2 and pid_ns_prepare_proc() won't be called. So, pid_namespace::proc_mnt will never be initialized (not to mention that there won't be a child reaper). I saw crash stack of such case on kernel 3.10: BUG: unable to handle kernel NULL pointer dereference at (null) IP: proc_flush_task+0x8f/0x1b0 Call Trace: release_task+0x3f/0x490 wait_consider_task.part.10+0x7ff/0xb00 do_wait+0x11f/0x280 SyS_wait4+0x7d/0x110 We may fix this by restore of last_pid in 0 or by prohibiting of futher allocations. Since there was a similar issue in Oleg Nesterov's commit 314a8ad0f18a ("pidns: fix free_pid() to handle the first fork failure"). and it was fixed via prohibiting allocation, let's follow this way, and do the same. Link: http://lkml.kernel.org/r/149201021004.4863.6762095011554287922.stgit@= localhost.localdomain Signed-off-by: Kirill Tkhai Acked-by: Cyrill Gorcunov Cc: Andrei Vagin Cc: Andreas Gruenbacher Cc: Kees Cook Cc: Michael Kerrisk Cc: Al Viro Cc: Oleg Nesterov Cc: Paul Moore Cc: Eric Biederman Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Serge Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- kernel/pid.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/pid.c b/kernel/pid.c index 693a64385d59..fa704f88ff8e 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -322,8 +322,10 @@ struct pid *alloc_pid(struct pid_namespace *ns) } =20 if (unlikely(is_child_reaper(pid))) { - if (pid_ns_prepare_proc(ns)) + if (pid_ns_prepare_proc(ns)) { + disable_pid_allocation(ns); goto out_free; + } } =20 get_pid_ns(ns); --=20 2.14.1