From owner-freebsd-bugs@freebsd.org Sat Nov 18 14:09:02 2017 Return-Path: Delivered-To: freebsd-bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id C02C2DBBC06 for ; Sat, 18 Nov 2017 14:09:02 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 9C61670BE4 for ; Sat, 18 Nov 2017 14:09:02 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id vAIE92hg085771 for ; Sat, 18 Nov 2017 14:09:02 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 223732] mmap(2) causes unkillable denial of service with specific flags Date: Sat, 18 Nov 2017 14:09:02 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 11.1-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: aksyom@gmail.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter attachments.created Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Nov 2017 14:09:02 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D223732 Bug ID: 223732 Summary: mmap(2) causes unkillable denial of service with specific flags Product: Base System Version: 11.1-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Many People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: aksyom@gmail.com Created attachment 188093 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D188093&action= =3Dedit mmap(2) local denial of service with MAP_STACK|MAP_ALIGNED(N) flags I have found a set of flags that will cause a process to saturate an entire execution unit at 100% median while the process becomes unkillable even with kill -9. Sometimes the process might go under 100% CPU usage, but it gets b= ack too 100% after a while. The process state stays "running". This is effectiv= ely a perfect local denial of service, which cannot be undone by administrators= or counter-intrusion software. The only way to get out of this DoS is to reboot the entire system. Furthermore, if you the process a number of times greater than the number of physical CPU cores available to the system (at least on amd64), the system becomes totally unresponsive, and then only a forced power down from a power button is effective. To reproduce this denial of service, compile the following source code with clang and execute it: #include int main(int argc, char** argv) { void *stack =3D mmap(0, 1<<12, PROT_READ|PROT_WRITE, MAP_STACK|MAP_ALIGNED(12), -1, 0); /* Never reached. * Process will saturate one entire execution unit! * ALSO THIS PROCESS CANNOT BE KILLED!=20 *=20 * DoS manifests when the value of 2nd argument (len)=20 * is less than or equal to 1<