Date: Fri, 8 Mar 2013 19:31:05 GMT From: Adrian Chadd <adrian@FreeBSD.org> To: freebsd-gnats-submit@FreeBSD.org Subject: misc/176764: [net] [if_bridge] use-after-free in if_bridge Message-ID: <201303081931.r28JV5B9070805@red.freebsd.org> Resent-Message-ID: <201303081940.r28Je3mZ034132@freefall.freebsd.org>
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>Number: 176764
>Category: misc
>Synopsis: [net] [if_bridge] use-after-free in if_bridge
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Mar 08 19:40:03 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Adrian Chadd
>Release:
>Organization:
>Environment:
>Description:
Hi Adrian,
There seems to be a potential use-after-free in `sys/net/if_bridge.c'.
>From the following chunk of code:
#define GRAB_OUR_PACKETS(iface) \
if ((iface)->if_type == IFT_GIF) \
continue; \
/* It is destined for us. */ \
if (memcmp(IF_LLADDR((iface)), eh->ether_dhost, ETHER_ADDR_LEN) == 0 \
OR_CARP_CHECK_WE_ARE_DST((iface)) \
) { \
if ((iface)->if_type == IFT_BRIDGE) { \
ETHER_BPF_MTAP(iface, m); \
iface->if_ipackets++; \
/* Filter on the physical interface. */ \
if (pfil_local_phys && \
(PFIL_HOOKED(&V_inet_pfil_hook) \
OR_PFIL_HOOKED_INET6)) { \
if (bridge_pfil(&m, NULL, ifp, \
PFIL_IN) != 0 || m == NULL) { \
BRIDGE_UNLOCK(sc); \
return (NULL); \
} \
} \
} \
bridge_pfil() might end-up changing the mbuf pointer (and the
underlying data), however, we still have a pending pointer to the data
through `eh' which is about to be dereferenced in the following call
to bridge_rtupdate():
if (bif->bif_flags & IFBIF_LEARNING) { \
error = bridge_rtupdate(sc, eh->ether_shost, \
vlan, bif, 0, IFBAF_DYNAMIC); \
The obvious patch to fix this is attached to this mail.
>How-To-Repeat:
n/a
>Fix:
see attachment
Patch attached with submission follows:
diff --git a/sys/net/if_bridge.c b/sys/net/if_bridge.c
index 85ad9fb..73ee550 100644
--- a/sys/net/if_bridge.c
+++ b/sys/net/if_bridge.c
@@ -2313,6 +2313,7 @@ bridge_input(struct ifnet *ifp, struct mbuf *m)
BRIDGE_UNLOCK(sc); \
return (NULL); \
} \
+ eh = mtod(m, struct ether_header *); \
} \
} \
if (bif->bif_flags & IFBIF_LEARNING) { \
>Release-Note:
>Audit-Trail:
>Unformatted:
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