batman-adv: Fix deletion of RTR(4|6) mcast list entries
diff mbox series

Message ID 20190707210457.20892-1-sven@narfation.org
State Accepted, archived
Commit 230222a7acd5fcea4471b1c2411fc9d7da9ebb0f
Delegated to: Simon Wunderlich
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Series
  • batman-adv: Fix deletion of RTR(4|6) mcast list entries
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Commit Message

Sven Eckelmann July 7, 2019, 9:04 p.m. UTC
The multicast code uses the lists bat_priv->mcast.want_all_rtr*_list to
store all all originator nodes which don't have the flag no-RTR4 or no-RTR6
set. When an originator is purged, it has to be removed from these lists.

Since all entries without the BATADV_MCAST_WANT_NO_RTR4/6 are stored in
these lists, they have to be handled like entries which have these flags
set to force the update routines to remove them from the lists when purging
the originator.

Not doing so will leave a pointer to a freed memory region inside the list.
Trying to operate on these lists will then cause an use-after-free error:

  BUG: KASAN: use-after-free in batadv_mcast_want_rtr4_update+0x335/0x3a0 [batman_adv]
  Write of size 8 at addr ffff888007b41a38 by task swapper/0/0

Fixes: 0a7733468f95 ("batman-adv: mcast: detect, distribute and maintain multicast router presence")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
Cc: Linus Lüssing <linus.luessing@c0d3.blue>

See https://www.open-mesh.org/issues/395
---
 net/batman-adv/multicast.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Linus Lüssing July 7, 2019, 9:47 p.m. UTC | #1
On Sun, Jul 07, 2019 at 11:04:57PM +0200, Sven Eckelmann wrote:
> The multicast code uses the lists bat_priv->mcast.want_all_rtr*_list to
> store all all originator nodes which don't have the flag no-RTR4 or no-RTR6
> set. When an originator is purged, it has to be removed from these lists.
> 
> Since all entries without the BATADV_MCAST_WANT_NO_RTR4/6 are stored in
> these lists, they have to be handled like entries which have these flags
> set to force the update routines to remove them from the lists when purging
> the originator.
> 
> Not doing so will leave a pointer to a freed memory region inside the list.
> Trying to operate on these lists will then cause an use-after-free error:
> 
>   BUG: KASAN: use-after-free in batadv_mcast_want_rtr4_update+0x335/0x3a0 [batman_adv]
>   Write of size 8 at addr ffff888007b41a38 by task swapper/0/0
> 
> Fixes: 0a7733468f95 ("batman-adv: mcast: detect, distribute and maintain multicast router presence")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
> Cc: Linus Lüssing <linus.luessing@c0d3.blue>
> 
> See https://www.open-mesh.org/issues/395
> ---

Acked-by: Linus Lüssing <linus.luessing@c0d3.blue>

Patch
diff mbox series

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index a3488cfb..1d5bdf3a 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -2420,8 +2420,10 @@  void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
 	batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);
 	batadv_mcast_want_ipv4_update(bat_priv, orig, BATADV_NO_FLAGS);
 	batadv_mcast_want_ipv6_update(bat_priv, orig, BATADV_NO_FLAGS);
-	batadv_mcast_want_rtr4_update(bat_priv, orig, BATADV_NO_FLAGS);
-	batadv_mcast_want_rtr6_update(bat_priv, orig, BATADV_NO_FLAGS);
+	batadv_mcast_want_rtr4_update(bat_priv, orig,
+				      BATADV_MCAST_WANT_NO_RTR4);
+	batadv_mcast_want_rtr6_update(bat_priv, orig,
+				      BATADV_MCAST_WANT_NO_RTR6);
 
 	spin_unlock_bh(&orig->mcast_handler_lock);
 }