Date: Mon, 4 Jun 2012 12:36:59 +0000 (UTC) From: "Alexander V. Chernikov" <melifaro@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r236559 - head/sys/net Message-ID: <201206041236.q54CaxO1041508@svn.freebsd.org>
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Author: melifaro Date: Mon Jun 4 12:36:58 2012 New Revision: 236559 URL: http://svn.freebsd.org/changeset/base/236559 Log: Fix panic introduced by r235745. Panic occurs after first packet traverse renamed interface. Add several comments on locking Found by: avg Approved by: ae(mentor) Tested by: avg MFC after: 1 week Modified: head/sys/net/bpf.c Modified: head/sys/net/bpf.c ============================================================================== --- head/sys/net/bpf.c Mon Jun 4 12:28:56 2012 (r236558) +++ head/sys/net/bpf.c Mon Jun 4 12:36:58 2012 (r236559) @@ -1704,6 +1704,14 @@ bpfioctl(struct cdev *dev, u_long cmd, c /* * Set d's packet filter program to fp. If this file already has a filter, * free it and replace it. Returns EINVAL for bogus requests. + * + * Note we need global lock here to serialize bpf_setf() and bpf_setif() calls + * since reading d->bd_bif can't be protected by d or interface lock due to + * lock order. + * + * Additionally, we have to acquire interface write lock due to bpf_mtap() uses + * interface read lock to read all filers. + * */ static int bpf_setf(struct bpf_d *d, struct bpf_program *fp, u_long cmd) @@ -2535,20 +2543,32 @@ bpfdetach(struct ifnet *ifp) } /* - * Interface departure handler + * Interface departure handler. + * Note departure event does not guagantee interface is going down. */ static void bpf_ifdetach(void *arg __unused, struct ifnet *ifp) { struct bpf_if *bp; - if ((bp = ifp->if_bpf) == NULL) + BPF_LOCK(); + if ((bp = ifp->if_bpf) == NULL) { + BPF_UNLOCK(); + return; + } + + /* Check if bpfdetach() was called previously */ + if ((bp->flags & BPFIF_FLAG_DYING) == 0) { + BPF_UNLOCK(); return; + } CTR3(KTR_NET, "%s: freing BPF instance %p for interface %p", __func__, bp, ifp); ifp->if_bpf = NULL; + BPF_UNLOCK(); + rw_destroy(&bp->bif_lock); free(bp, M_BPF); }
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