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Add dead_bpf_if structure, that should be used as fake bpf_if

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during ifnet detach.

Since destroying interface is not atomic operation and due to the
lack of synhronization during destroy, it is possible, that in the
time between bpfdetach() and if_free() some queued on destroying
interface mbuf will be used by ether_input_internal() and
bpf_peers_present() can dereference NULL bpf_if pointer. To protect
from this, assign pointer to empty bpf_if_ext structure instead of
NULL pointer after bpfdetach().

Reviewed by:	melifaro, eugen
Obtained from:	Yandex LLC
MFC after:	1 week
Sponsored by:	Yandex LLC
Differential Revision:	https://reviews.freebsd.org/D15083
This commit is contained in:
Andrey V. Elsukov 2018-04-20 09:57:31 +00:00
parent d83f17e5f9
commit 2b9600b449
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=332812
1 changed files with 5 additions and 1 deletions
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6
sys/net/bpf.c
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@ -98,6 +98,10 @@ __FBSDID("$FreeBSD$");
MALLOC_DEFINE(M_BPF, "BPF", "BPF data");
static struct bpf_if_ext dead_bpf_if = {
.bif_dlist = LIST_HEAD_INITIALIZER()
};
struct bpf_if {
#define bif_next bif_ext.bif_next
#define bif_dlist bif_ext.bif_dlist
@ -2659,7 +2663,7 @@ bpfdetach(struct ifnet *ifp)
*/
BPFIF_WLOCK(bp);
bp->bif_flags |= BPFIF_FLAG_DYING;
*bp->bif_bpf = NULL;
*bp->bif_bpf = (struct bpf_if *)&dead_bpf_if;;
BPFIF_WUNLOCK(bp);
CTR4(KTR_NET, "%s: sheduling free for encap %d (%p) for if %p",