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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 S966055AbeCSQHC (ORCPT ); Mon, 19 Mar 2018 12:07:02 -0400 Received: from mail-cys01nam02on0100.outbound.protection.outlook.com ([104.47.37.100]:20505 "EHLO NAM02-CY1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966065AbeCSQGu (ORCPT ); Mon, 19 Mar 2018 12:06:50 -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 4.4 016/167] pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid() Thread-Topic: [PATCH AUTOSEL for 4.4 016/167] pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid() Thread-Index: AQHTv5whIYVhVopSOkGIfL7hAX/InA== Date: Mon, 19 Mar 2018 16:05:41 +0000 Message-ID: <20180319160513.16384-16-alexander.levin@microsoft.com> References: <20180319160513.16384-1-alexander.levin@microsoft.com> In-Reply-To: <20180319160513.16384-1-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;DM5PR2101MB1093;7:3ncTj/KZBe9rl9XOsCV69/4jdXxvFvKAmMxF4DbJUdb/XxE3fEHVfNhA4kz/Op577yyc9j0EBx/jx9+7ZlPo/cSKgMzXSDk2huBsxzUcXyPDnXXxRwduoRCmdm7JmrlMhlkQ5vphj0Tdn2xHjXLZSSsMCoZB6V5UxW0R7ekurGZwUnmZbh4FcNp11VS7Ni7Yu4WUT8EcIi1o64WUCIsOyj50xz1FhXN8sKXpHOeziJp/Zj7sE0OFaau1LaO85AcD;20:GwY2/QMbxibNYdLwrbG7IrCQNHtAOo2EZ8efZKYUcJv3xq0lEwBDxbITtofE0q7tDHKCTHrsMI4PuvD8OYmA+9EBk+PxHmTXZT9LO5pTVvIulx9nSV/A2Ur0al4YScTRSltvEflYQ8s5ixQBSZx1tb7PeX9S7xJOGhSl6zXEjEs= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 256c58ad-4d8d-41fb-365e-08d58db36b05 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1093; 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x-microsoft-antispam-message-info: cHIpSHExcMYCXg271ID6xJZqH0WjCCw+Rrw2xJ4XnSlbbMtSzsGXYK70qTUz1wYs1kgqRq3U5VGOmT20ne9z7FigOrd46bl4B7RtuoOTcgWqij3mK0nrthUUDFcRMgm0N/iJYZPCHlU77WMKimK0LOevwPiqSNZrD63ds3Gqe2b1cSRJnXc1vlrI5QCnNTGg8WlbUqZT3P9OHbvaactI+ef4nNqRzPPrq7eRmt9Mp1lxVRgkNtd43x5o35rAI8cCRAucd6pwYtjnlNmgTjZWwNHrpiQXw3uH0ABi+D9m1yBAEpOcnQgsABcSMSKzr0Ghw9jANinB3xrocelwUzvqWA== 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: 256c58ad-4d8d-41fb-365e-08d58db36b05 X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:05:41.9743 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1093 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 b17263be9082..5fe7cdb6d05f 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