From owner-freebsd-bugs@freebsd.org Fri Jan 20 22:18:05 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 7DB93CB93E1 for ; Fri, 20 Jan 2017 22:18:05 +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 6DAE21167 for ; Fri, 20 Jan 2017 22:18:05 +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 v0KMI4D1075084 for ; Fri, 20 Jan 2017 22:18:05 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 216304] Adding xn0 to bridge0 causes kernel panic Date: Fri, 20 Jan 2017 22:18:05 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 11.0-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: kp@freebsd.org 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: cc Message-ID: In-Reply-To: References: 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: Fri, 20 Jan 2017 22:18:05 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D216304 Kristof Provost changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |royger@freebsd.org --- Comment #2 from Kristof Provost --- I think what happens here is that the bridge code (through bridge_ioctl_add= () calls the xen driver's ioctl() handler for SIOCSIFCAP, which through xn_ioc= tl() calls xs_rm(xenbus_get_node(dev), "feature-gso-tcp4"), which tries to compo= se a string with the sbuf functions, which use a M_WAITOK allocation. That means that we can end up sleeping (because malloc(M_WAITOK)) with the bridge lock (a standard mutex) held. That violates locking rules, by sleeping with a mutex held, so WITNESS warn= s us about this. If we're unlucky enough to actually try to acquire the bridge lock from ano= ther thread (say because we want to transmit a packet) we can end up panic()ing. It's not obvious to me how this can be fixed however. I'm cc-ing royger bec= ause he touched the xen-netfront code at some point. Perhaps we can allocate the strings the xs_rm() needs at device initialisat= ion time, but that would require the result of xenbus_get_node(dev) to be const= ant, and I don't know if that's a valid assumption. --=20 You are receiving this mail because: You are the assignee for the bug.=