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bpf: Fix incorrect cleanup

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Cleaning up a bpf_if is a two stage process. We first move it to the
bpf_freelist (in bpfdetach()) and only later do we actually free it (in
bpf_ifdetach()).

We cannot set the ifp->if_bpf to NULL from bpf_ifdetach() because it's
possible that the ifnet has already gone away, or that it has been assigned
a new bpf_if.
This can lead to a struct ifnet which is up, but has if_bpf set to NULL,
which will panic when we try to send the next packet.

Keep track of the pointer to the bpf_if (because it's not always
ifp->if_bpf), and NULL it immediately in bpfdetach().

PR:		213896
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D11782
This commit is contained in:
Kristof Provost 2017-08-16 19:40:07 +00:00
parent f8de17a11f
commit 9ce40d321d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=322590
1 changed files with 3 additions and 7 deletions
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10
sys/net/bpf.c
View file

@ -106,6 +106,7 @@ struct bpf_if {
struct rwlock bif_lock; /* interface lock */
LIST_HEAD(, bpf_d) bif_wlist; /* writer-only list */
int bif_flags; /* Interface flags */
struct bpf_if **bif_bpf; /* Pointer to pointer to us */
};
CTASSERT(offsetof(struct bpf_if, bif_ext) == 0);
@ -2563,6 +2564,7 @@ bpfattach2(struct ifnet *ifp, u_int dlt, u_int hdrlen, struct bpf_if **driverp)
bp->bif_dlt = dlt;
rw_init(&bp->bif_lock, "bpf interface lock");
KASSERT(*driverp == NULL, ("bpfattach2: driverp already initialized"));
bp->bif_bpf = driverp;
*driverp = bp;
BPF_LOCK();
@ -2633,6 +2635,7 @@ bpfdetach(struct ifnet *ifp)
*/
BPFIF_WLOCK(bp);
bp->bif_flags |= BPFIF_FLAG_DYING;
*bp->bif_bpf = NULL;
BPFIF_WUNLOCK(bp);
CTR4(KTR_NET, "%s: sheduling free for encap %d (%p) for if %p",
@ -2702,13 +2705,6 @@ bpf_ifdetach(void *arg __unused, struct ifnet *ifp)
nmatched++;
}
BPF_UNLOCK();
/*
* Note that we cannot zero other pointers to
* custom DLTs possibly used by given interface.
*/
if (nmatched != 0)
ifp->if_bpf = NULL;
}
/*