From owner-freebsd-bugs@freebsd.org Mon Feb 27 16:51:27 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 21ACDCF0E3E for ; Mon, 27 Feb 2017 16:51:27 +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 EAB562A5 for ; Mon, 27 Feb 2017 16:51:26 +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 v1RGpQep016200 for ; Mon, 27 Feb 2017 16:51:26 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 217401] Deadlock in if_clone.c Date: Mon, 27 Feb 2017 16:51:27 +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: 10.3-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: FreeBSD-prs@Vitsch.nl 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 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: 2.1.23 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Feb 2017 16:51:27 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D217401 Bug ID: 217401 Summary: Deadlock in if_clone.c Product: Base System Version: 10.3-STABLE Hardware: Any OS: Any Status: New Severity: Affects Many People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: FreeBSD-prs@Vitsch.nl The code in if_clone.c uses the unit number allocator subsystem to keep tra= ck of free unit numbers when allocating interfaces. This can get out of sync w= ith reality since interfaces can be renamed after creation. When this happens, = the retry loop in if_alloc_unit() can deadlock a system. The following set of commands will deadlock FreeBSD: ifconfig bridge create ifconfig bridge create ifconfig bridge1 name bridge3 ifconfig bridge create ifconfig bridge create ifconfig bridge create # (deadlock at this point) The deadlock happens when alloc_unr_specific() returns an unused unit numbe= r, but the later call to ifunit(name) sees that the unit is already in use. In this case, the code will increase '*unit' and loop back to 'retry:'. If = this increased '*unit' number is already allocated, the return value of the next call to alloc_unr_specific() will override '*unit' and leave it at -1. The code will then increase '*unit' again and loop back to 'retry:' again w= ith '*unit' now set to 0. If unit number 0 also already exists, we'll be caught= in an infinite loop. The attached patch fixes the deadlock by simply not destroying the value of '*unit' before incrementing it in the 'retry' path. (This is a slight variant of kern/162789. The same use case that triggered = that bug now also triggers this deadlock.) --=20 You are receiving this mail because: You are the assignee for the bug.=