From c2e703a55245bfff3db53b1f7cbe59f1ee8a4339 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Tue, 17 Nov 2015 14:25:21 +0100 Subject: [PATCH] mac80211: mesh: fix call_rcu() usage 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. Cc: stable@vger.kernel.org Fixes: eb2b9311fd00 ("mac80211: mesh path table implementation") Reported-by: Jouni Malinen Signed-off-by: Johannes Berg --- net/mac80211/mesh_pathtbl.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c index b890e225a8f1..b3b44a5dd375 100644 --- a/net/mac80211/mesh_pathtbl.c +++ b/net/mac80211/mesh_pathtbl.c @@ -779,10 +779,8 @@ void mesh_plink_broken(struct sta_info *sta) 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(struct rcu_head *rp) /* 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_table *tbl, struct mpath_node *node) 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); } -- 2.20.1