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epair: Do not abuse params to register the second interface

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if_epair used the 'params' argument to pass a pointer to the b interface
through if_clone_create().
This pointer can be controlled by userspace, which means it could be abused to
trigger a panic. While this requires PRIV_NET_IFCREATE
privileges those are assigned to vnet jails, which means that vnet jails
could panic the system.

Reported by:	Ilja Van Sprundel <ivansprundel@ioactive.com>
MFC after:	3 days
This commit is contained in:
Kristof Provost 2020-01-28 22:44:24 +00:00
parent 1232c36139
commit b02fd8b790
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=357233
3 changed files with 35 additions and 29 deletions
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19
sys/net/if_clone.c
View File

@ -211,6 +211,18 @@ if_clone_create(char *name, size_t len, caddr_t params)
return (if_clone_createif(ifc, name, len, params));
}
void
if_clone_addif(struct if_clone *ifc, struct ifnet *ifp)
{
if ((ifc->ifc_flags & IFC_NOGROUP) == 0)
if_addgroup(ifp, ifc->ifc_name);
IF_CLONE_LOCK(ifc);
IFC_IFLIST_INSERT(ifc, ifp);
IF_CLONE_UNLOCK(ifc);
}
/*
* Create a clone network interface.
*/
@ -233,12 +245,7 @@ if_clone_createif(struct if_clone *ifc, char *name, size_t len, caddr_t params)
if (ifp == NULL)
panic("%s: lookup failed for %s", __func__, name);
if ((ifc->ifc_flags & IFC_NOGROUP) == 0)
if_addgroup(ifp, ifc->ifc_name);
IF_CLONE_LOCK(ifc);
IFC_IFLIST_INSERT(ifc, ifp);
IF_CLONE_UNLOCK(ifc);
if_clone_addif(ifc, ifp);
}
return (err);

3
sys/net/if_clone.h
View File

@ -79,7 +79,8 @@ int if_clone_list(struct if_clonereq *);
struct if_clone *if_clone_findifc(struct ifnet *);
void if_clone_addgroup(struct ifnet *, struct if_clone *);
/* The below interface used only by epair(4). */
/* The below interfaces are used only by epair(4). */
void if_clone_addif(struct if_clone *, struct ifnet *);
int if_clone_destroyif(struct if_clone *, struct ifnet *);
#endif /* _KERNEL */

42
sys/net/if_epair.c
View File

@ -711,6 +711,21 @@ epair_clone_match(struct if_clone *ifc, const char *name)
return (1);
}
static void
epair_clone_add(struct if_clone *ifc, struct epair_softc *scb)
{
struct ifnet *ifp;
uint8_t eaddr[ETHER_ADDR_LEN]; /* 00:00:00:00:00:00 */
ifp = scb->ifp;
/* Copy epairNa etheraddr and change the last byte. */
memcpy(eaddr, scb->oifp->if_hw_addr, ETHER_ADDR_LEN);
eaddr[5] = 0x0b;
ether_ifattach(ifp, eaddr);
if_clone_addif(ifc, ifp);
}
static int
epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
{
@ -723,24 +738,6 @@ epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
uint32_t hash;
uint8_t eaddr[ETHER_ADDR_LEN]; /* 00:00:00:00:00:00 */
/*
* We are abusing params to create our second interface.
* Actually we already created it and called if_clone_create()
* for it to do the official insertion procedure the moment we knew
* it cannot fail anymore. So just do attach it here.
*/
if (params) {
scb = (struct epair_softc *)params;
ifp = scb->ifp;
/* Copy epairNa etheraddr and change the last byte. */
memcpy(eaddr, scb->oifp->if_hw_addr, ETHER_ADDR_LEN);
eaddr[5] = 0x0b;
ether_ifattach(ifp, eaddr);
/* Correctly set the name for the cloner list. */
strlcpy(name, ifp->if_xname, len);
return (0);
}
/* Try to see if a special unit was requested. */
error = ifc_name2unit(name, &unit);
if (error != 0)
@ -891,10 +888,11 @@ epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
if_setsendqready(ifp);
/* We need to play some tricks here for the second interface. */
strlcpy(name, epairname, len);
error = if_clone_create(name, len, (caddr_t)scb);
if (error)
panic("%s: if_clone_create() for our 2nd iface failed: %d",
__func__, error);
/* Correctly set the name for the cloner list. */
strlcpy(name, scb->ifp->if_xname, len);
epair_clone_add(ifc, scb);
scb->if_qflush = ifp->if_qflush;
ifp->if_qflush = epair_qflush;
ifp->if_transmit = epair_transmit;