linux-kernel - [PATCH 3.2 14/77] mac80211: mesh: fix call

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1450971462.87361541@decadent.org.uk>
Date:	Thu, 24 Dec 2015 15:37:42 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Jouni Malinen" <j@...fi>,
	"Johannes Berg" <johannes.berg@...el.com>
Subject: [PATCH 3.2 14/77] mac80211: mesh: fix call_rcu() usage

3.2.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Berg <johannes.berg@...el.com>

commit c2e703a55245bfff3db53b1f7cbe59f1ee8a4339 upstream.

When using call_rcu(), the called function may be delayed quite
significantly, and without a matching rcu_barrier() there's no
way to be sure it has finished.
Therefore, global state that could be gone/freed/reused should
never be touched in the callback.

Fix this in mesh by moving the atomic_dec() into the caller;
that's not really a problem since we already unlinked the path
and it will be destroyed anyway.

This fixes a crash Jouni observed when running certain tests in
a certain order, in which the mesh interface was torn down, the
memory reused for a function pointer (work struct) and running
that then crashed since the pointer had been decremented by 1,
resulting in an invalid instruction byte stream.

Fixes: eb2b9311fd00 ("mac80211: mesh path table implementation")
Reported-by: Jouni Malinen <j@...fi>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/mac80211/mesh_pathtbl.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -779,10 +779,8 @@ void mesh_plink_broken(struct sta_info *
 static void mesh_path_node_reclaim(struct rcu_head *rp)
 {
 	struct mpath_node *node = container_of(rp, struct mpath_node, rcu);
-	struct ieee80211_sub_if_data *sdata = node->mpath->sdata;
 
 	del_timer_sync(&node->mpath->timer);
-	atomic_dec(&sdata->u.mesh.mpaths);
 	kfree(node->mpath);
 	kfree(node);
 }
@@ -790,8 +788,9 @@ static void mesh_path_node_reclaim(struc
 /* needs to be called with the corresponding hashwlock taken */
 static void __mesh_path_del(struct mesh_table *tbl, struct mpath_node *node)
 {
-	struct mesh_path *mpath;
-	mpath = node->mpath;
+	struct mesh_path *mpath = node->mpath;
+	struct ieee80211_sub_if_data *sdata = node->mpath->sdata;
+
 	spin_lock(&mpath->state_lock);
 	mpath->flags |= MESH_PATH_RESOLVING;
 	if (mpath->is_gate)
@@ -799,6 +798,7 @@ static void __mesh_path_del(struct mesh_
 	hlist_del_rcu(&node->list);
 	call_rcu(&node->rcu, mesh_path_node_reclaim);
 	spin_unlock(&mpath->state_lock);
+	atomic_dec(&sdata->u.mesh.mpaths);
 	atomic_dec(&tbl->entries);
 }
 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/