[PATCH 0/2] mac80211: Fix incorrect usage of rhashtable walk API

[PATCH 0/2] mac80211: Fix incorrect usage of rhashtable walk API

[Herbert Xu]

Hi:

This patch fixes a number of issues with the use of the rhashtable API
in mac80211.  First of all it converts the use of rashtable walks over
to a simple linked list.  This is because an rhashtable walk is
inherently unstable and not meant for uses that require stability,
e.g., when you're trying to lookup an object to delete.

It also fixes a potential memory leak when the rhashtable insertion
fails (which can occur due to OOM).

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH 1/2] mac80211: Use linked list instead of rhashtable walk for mesh tables

[Herbert Xu]

The mesh table code walks over hash tables for two purposes.  First of
all it's used as part of a netlink dump process, but it is also used
for looking up entries to delete using criteria other than the hash
key.

The second purpose is directly contrary to the design specification
of rhashtable walks.  It is only meant for use by netlink dumps.

This is because rhashtable is resizable and you cannot obtain a
stable walk over it during a resize process.

In fact mesh's use of rhashtable for dumping is bogus too.  Rather
than using rhashtable walk's iterator to keep track of the current
position, it always converts the current position to an integer
which defeats the purpose of the iterator.

Therefore this patch converts all uses of rhashtable walk into a
simple linked list.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh.h         |    4 +
 net/mac80211/mesh_pathtbl.c |  119 +++++++-------------------------------------
 2 files changed, 24 insertions(+), 99 deletions(-)

diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index cad6592c52a1..d8e626d66055 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -70,6 +70,7 @@ enum mesh_deferred_task_flags {
  * @dst: mesh path destination mac address
  * @mpp: mesh proxy mac address
  * @rhash: rhashtable list pointer
+ * @walk_list: linked list containing all mesh_path objects.
  * @gate_list: list pointer for known gates list
  * @sdata: mesh subif
  * @next_hop: mesh neighbor to which frames for this destination will be
@@ -105,6 +106,7 @@ struct mesh_path {
 	u8 dst[ETH_ALEN];
 	u8 mpp[ETH_ALEN];	/* used for MPP or MAP */
 	struct rhash_head rhash;
+	struct hlist_node walk_list;
 	struct hlist_node gate_list;
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info __rcu *next_hop;
@@ -133,12 +135,14 @@ struct mesh_path {
  * gate's mpath may or may not be resolved and active.
  * @gates_lock: protects updates to known_gates
  * @rhead: the rhashtable containing struct mesh_paths, keyed by dest addr
+ * @walk_head: linked list containging all mesh_path objects
  * @entries: number of entries in the table
  */
 struct mesh_table {
 	struct hlist_head known_gates;
 	spinlock_t gates_lock;
 	struct rhashtable rhead;
+	struct hlist_head walk_head;
 	atomic_t entries;		/* Up to MAX_MESH_NEIGHBOURS */
 };
 
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index a5125624a76d..984ed433a8bc 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -249,28 +249,15 @@ mpp_path_lookup(struct ieee80211_sub_if_data *sdata, const u8 *dst)
 static struct mesh_path *
 __mesh_path_lookup_by_idx(struct mesh_table *tbl, int idx)
 {
-	int i = 0, ret;
-	struct mesh_path *mpath = NULL;
-	struct rhashtable_iter iter;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return NULL;
-
-	rhashtable_walk_start(&iter);
+	int i = 0;
+	struct mesh_path *mpath;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	hlist_for_each_entry(mpath, &tbl->walk_head, walk_list) {
 		if (i++ == idx)
 			break;
 	}
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 
-	if (IS_ERR(mpath) || !mpath)
+	if (!mpath)
 		return NULL;
 
 	if (mpath_expired(mpath)) {
@@ -441,7 +428,8 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 			mpath = rhashtable_lookup_fast(&tbl->rhead,
 						       dst,
 						       mesh_rht_params);
-
+		else if (!ret)
+			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 	} while (unlikely(ret == -EEXIST && !mpath));
 
 	if (ret && ret != -EEXIST)
@@ -483,6 +471,8 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata,
 	ret = rhashtable_lookup_insert_fast(&tbl->rhead,
 					    &new_mpath->rhash,
 					    mesh_rht_params);
+	if (!ret)
+		hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 
 	sdata->u.mesh.mpp_paths_generation++;
 	return ret;
@@ -503,20 +493,8 @@ void mesh_plink_broken(struct sta_info *sta)
 	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
 	static const u8 bcast[ETH_ALEN] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	hlist_for_each_entry(mpath, &tbl->walk_head, walk_list) {
 		if (rcu_access_pointer(mpath->next_hop) == sta &&
 		    mpath->flags & MESH_PATH_ACTIVE &&
 		    !(mpath->flags & MESH_PATH_FIXED)) {
@@ -530,8 +508,6 @@ void mesh_plink_broken(struct sta_info *sta)
 				WLAN_REASON_MESH_PATH_DEST_UNREACHABLE, bcast);
 		}
 	}
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 }
 
 static void mesh_path_free_rcu(struct mesh_table *tbl,
@@ -551,6 +527,7 @@ static void mesh_path_free_rcu(struct mesh_table *tbl,
 
 static void __mesh_path_del(struct mesh_table *tbl, struct mesh_path *mpath)
 {
+	hlist_del(&mpath->walk_list);
 	rhashtable_remove_fast(&tbl->rhead, &mpath->rhash, mesh_rht_params);
 	mesh_path_free_rcu(tbl, mpath);
 }
@@ -571,27 +548,12 @@ void mesh_path_flush_by_nexthop(struct sta_info *sta)
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	struct hlist_node *n;
 
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if (rcu_access_pointer(mpath->next_hop) == sta)
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 }
 
 static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
@@ -599,51 +561,22 @@ static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
 {
 	struct mesh_table *tbl = sdata->u.mesh.mpp_paths;
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	struct hlist_node *n;
 
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if (ether_addr_equal(mpath->mpp, proxy))
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 }
 
 static void table_flush_by_iface(struct mesh_table *tbl)
 {
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
+	struct hlist_node *n;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 }
 
 /**
@@ -838,6 +771,8 @@ int mesh_pathtbl_init(struct ieee80211_sub_if_data *sdata)
 
 	rhashtable_init(&tbl_path->rhead, &mesh_rht_params);
 	rhashtable_init(&tbl_mpp->rhead, &mesh_rht_params);
+	INIT_HLIST_HEAD(&tbl_path->walk_head);
+	INIT_HLIST_HEAD(&tbl_mpp->walk_head);
 
 	sdata->u.mesh.mesh_paths = tbl_path;
 	sdata->u.mesh.mpp_paths = tbl_mpp;
@@ -854,28 +789,14 @@ void mesh_path_tbl_expire(struct ieee80211_sub_if_data *sdata,
 			  struct mesh_table *tbl)
 {
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_KERNEL);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
+	struct hlist_node *n;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
 		    (!(mpath->flags & MESH_PATH_FIXED)) &&
 		     time_after(jiffies, mpath->exp_time + MESH_PATH_EXPIRE))
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 }
 
 void mesh_path_expire(struct ieee80211_sub_if_data *sdata)

Re: [PATCH 1/2] mac80211: Use linked list instead of rhashtable walk for mesh tables

[Herbert Xu]

On Wed, Feb 13, 2019 at 01:16:13PM +0800, Herbert Xu wrote:
> The mesh table code walks over hash tables for two purposes.  First of
> all it's used as part of a netlink dump process, but it is also used
> for looking up entries to delete using criteria other than the hash
> key.
> 
> The second purpose is directly contrary to the design specification
> of rhashtable walks.  It is only meant for use by netlink dumps.
> 
> This is because rhashtable is resizable and you cannot obtain a
> stable walk over it during a resize process.
> 
> In fact mesh's use of rhashtable for dumping is bogus too.  Rather
> than using rhashtable walk's iterator to keep track of the current
> position, it always converts the current position to an integer
> which defeats the purpose of the iterator.
> 
> Therefore this patch converts all uses of rhashtable walk into a
> simple linked list.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

OK this patch is broken because there is no locking on the linked
list.  I'll repost the series.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH 2/2] mac80211: Free mpath object when rhashtable insertion fails

[Herbert Xu]

When rhashtable insertion fails the mesh table code doesn't free
the now-orphan mesh path object.  This patch fixes that.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh_pathtbl.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 984ed433a8bc..93fdd9a7d72c 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -432,17 +432,18 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 	} while (unlikely(ret == -EEXIST && !mpath));
 
-	if (ret && ret != -EEXIST)
+	if (ret)
+		kfree(new_mpath);
+
+	if (ret != -EEXIST)
 		return ERR_PTR(ret);
 
 	/* At this point either new_mpath was added, or we found a
 	 * matching entry already in the table; in the latter case
 	 * free the unnecessary new entry.
 	 */
-	if (ret == -EEXIST) {
-		kfree(new_mpath);
+	if (ret == -EEXIST)
 		new_mpath = mpath;
-	}
 	sdata->u.mesh.mesh_paths_generation++;
 	return new_mpath;
 }
@@ -473,6 +474,8 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata,
 					    mesh_rht_params);
 	if (!ret)
 		hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
+	else
+		kfree(new_mpath);
 
 	sdata->u.mesh.mpp_paths_generation++;
 	return ret;

Re: [PATCH 2/2] mac80211: Free mpath object when rhashtable insertion fails

[Dan Carpenter]

Hi Herbert,

url:    https://github.com/0day-ci/linux/commits/Herbert-Xu/mac80211-Fix-incorrect-usage-of-rhashtable-walk-API/20190213-181325
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git master

smatch warnings:
net/mac80211/mesh_pathtbl.c:439 mesh_path_add() warn: passing zero to 'ERR_PTR'

# https://github.com/0day-ci/linux/commit/a0886e834aacf883ceaf0c34c842c4cdb4d318fd
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout a0886e834aacf883ceaf0c34c842c4cdb4d318fd
vim +/ERR_PTR +439 net/mac80211/mesh_pathtbl.c

b15dc38b9 Bob Copeland         2016-02-28  390  
eb2b9311f Luis Carlos Cobo     2008-02-23  391  /**
eb2b9311f Luis Carlos Cobo     2008-02-23  392   * mesh_path_add - allocate and add a new path to the mesh path table
bf7cd94dc Johannes Berg        2013-02-15  393   * @dst: destination address of the path (ETH_ALEN length)
f698d856f Jasper Bryant-Greene 2008-08-03  394   * @sdata: local subif
eb2b9311f Luis Carlos Cobo     2008-02-23  395   *
af901ca18 André Goddard Rosa   2009-11-14  396   * Returns: 0 on success
eb2b9311f Luis Carlos Cobo     2008-02-23  397   *
eb2b9311f Luis Carlos Cobo     2008-02-23  398   * State: the initial state of the new path is set to 0
eb2b9311f Luis Carlos Cobo     2008-02-23  399   */
ae76eef02 Bob Copeland         2013-03-29  400  struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
ae76eef02 Bob Copeland         2013-03-29  401  				const u8 *dst)
eb2b9311f Luis Carlos Cobo     2008-02-23  402  {
349eb8cf4 Johannes Berg        2011-05-14  403  	struct mesh_table *tbl;
eb2b9311f Luis Carlos Cobo     2008-02-23  404  	struct mesh_path *mpath, *new_mpath;
60854fd94 Bob Copeland         2016-03-02  405  	int ret;
eb2b9311f Luis Carlos Cobo     2008-02-23  406  
b203ca391 Joe Perches          2012-05-08  407  	if (ether_addr_equal(dst, sdata->vif.addr))
eb2b9311f Luis Carlos Cobo     2008-02-23  408  		/* never add ourselves as neighbours */
ae76eef02 Bob Copeland         2013-03-29  409  		return ERR_PTR(-ENOTSUPP);
eb2b9311f Luis Carlos Cobo     2008-02-23  410  
eb2b9311f Luis Carlos Cobo     2008-02-23  411  	if (is_multicast_ether_addr(dst))
ae76eef02 Bob Copeland         2013-03-29  412  		return ERR_PTR(-ENOTSUPP);
eb2b9311f Luis Carlos Cobo     2008-02-23  413  
472dbc45d Johannes Berg        2008-09-11  414  	if (atomic_add_unless(&sdata->u.mesh.mpaths, 1, MESH_MAX_MPATHS) == 0)
ae76eef02 Bob Copeland         2013-03-29  415  		return ERR_PTR(-ENOSPC);
ae76eef02 Bob Copeland         2013-03-29  416  
b15dc38b9 Bob Copeland         2016-02-28  417  	new_mpath = mesh_path_new(sdata, dst, GFP_ATOMIC);
402d7752e Pavel Emelyanov      2008-05-06  418  	if (!new_mpath)
60854fd94 Bob Copeland         2016-03-02  419  		return ERR_PTR(-ENOMEM);
402d7752e Pavel Emelyanov      2008-05-06  420  
60854fd94 Bob Copeland         2016-03-02  421  	tbl = sdata->u.mesh.mesh_paths;
60854fd94 Bob Copeland         2016-03-02  422  	do {
60854fd94 Bob Copeland         2016-03-02  423  		ret = rhashtable_lookup_insert_fast(&tbl->rhead,
60854fd94 Bob Copeland         2016-03-02  424  						    &new_mpath->rhash,
60854fd94 Bob Copeland         2016-03-02  425  						    mesh_rht_params);
f84e71a94 Pavel Emelyanov      2008-05-06  426  
60854fd94 Bob Copeland         2016-03-02  427  		if (ret == -EEXIST)
60854fd94 Bob Copeland         2016-03-02  428  			mpath = rhashtable_lookup_fast(&tbl->rhead,
60854fd94 Bob Copeland         2016-03-02  429  						       dst,
60854fd94 Bob Copeland         2016-03-02  430  						       mesh_rht_params);
05b0152f1 Herbert Xu           2019-02-13  431  		else if (!ret)
05b0152f1 Herbert Xu           2019-02-13  432  			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
60854fd94 Bob Copeland         2016-03-02  433  	} while (unlikely(ret == -EEXIST && !mpath));
f5ea9120b Johannes Berg        2009-08-07  434  
a0886e834 Herbert Xu           2019-02-13  435  	if (ret)
a0886e834 Herbert Xu           2019-02-13  436  		kfree(new_mpath);
a0886e834 Herbert Xu           2019-02-13  437  
a0886e834 Herbert Xu           2019-02-13  438  	if (ret != -EEXIST)
60854fd94 Bob Copeland         2016-03-02 @439  		return ERR_PTR(ret);

                                                         if (ret && ret != -EEXIST) ?

ae76eef02 Bob Copeland         2013-03-29  440  
60854fd94 Bob Copeland         2016-03-02  441  	/* At this point either new_mpath was added, or we found a
60854fd94 Bob Copeland         2016-03-02  442  	 * matching entry already in the table; in the latter case
60854fd94 Bob Copeland         2016-03-02  443  	 * free the unnecessary new entry.
60854fd94 Bob Copeland         2016-03-02  444  	 */
a0886e834 Herbert Xu           2019-02-13  445  	if (ret == -EEXIST)
60854fd94 Bob Copeland         2016-03-02  446  		new_mpath = mpath;
60854fd94 Bob Copeland         2016-03-02  447  	sdata->u.mesh.mesh_paths_generation++;
60854fd94 Bob Copeland         2016-03-02  448  	return new_mpath;
18889231e Javier Cardona       2009-08-10  449  }
eb2b9311f Luis Carlos Cobo     2008-02-23  450  

:::::: The code at line 439 was first introduced by commit
:::::: 60854fd94573f0d3b80b55b40cf0140a0430f3ab mac80211: mesh: convert path table to rhashtable

:::::: TO: Bob Copeland <me@bobcopeland.com>
:::::: CC: Johannes Berg <johannes.berg@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[PATCH] mac80211: Use rhashtable_lookup_get_insert_fast instead of racy code

[Herbert Xu]

On Wed, Feb 13, 2019 at 01:05:51PM +0800, Herbert Xu wrote:
> Hi:
> 
> This patch fixes a number of issues with the use of the rhashtable API
> in mac80211.  First of all it converts the use of rashtable walks over
> to a simple linked list.  This is because an rhashtable walk is
> inherently unstable and not meant for uses that require stability,
> e.g., when you're trying to lookup an object to delete.
> 
> It also fixes a potential memory leak when the rhashtable insertion
> fails (which can occur due to OOM).

On top these two fixes here is one more clean-up patch to use an
existing rhashtable API instead of rolling its own racy version:

---8<---
The code in mesh_path_add tries to handle the case where a duplicate
entry is added to the rhashtable by doing a lookup after a failed
insertion.  It also tries to handle races by repeating the insertion
should the lookup fail.

This is now unnecessary as we have rhashtable API functions that can
directly return the mathcing object.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 93fdd9a7d72c..b06f066bfa01 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -402,7 +402,6 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 {
 	struct mesh_table *tbl;
 	struct mesh_path *mpath, *new_mpath;
-	int ret;
 
 	if (ether_addr_equal(dst, sdata->vif.addr))
 		/* never add ourselves as neighbours */
@@ -419,31 +418,21 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 		return ERR_PTR(-ENOMEM);
 
 	tbl = sdata->u.mesh.mesh_paths;
-	do {
-		ret = rhashtable_lookup_insert_fast(&tbl->rhead,
-						    &new_mpath->rhash,
-						    mesh_rht_params);
-
-		if (ret == -EEXIST)
-			mpath = rhashtable_lookup_fast(&tbl->rhead,
-						       dst,
-						       mesh_rht_params);
-		else if (!ret)
-			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
-	} while (unlikely(ret == -EEXIST && !mpath));
-
-	if (ret)
+	mpath = rhashtable_lookup_get_insert_fast(&tbl->rhead,
+						  &new_mpath->rhash,
+						  mesh_rht_params);
+	if (!mpath)
+		hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
+
+	if (mpath) {
 		kfree(new_mpath);
 
-	if (ret != -EEXIST)
-		return ERR_PTR(ret);
+		if (IS_ERR(mpath))
+			return mpath;
 
-	/* At this point either new_mpath was added, or we found a
-	 * matching entry already in the table; in the latter case
-	 * free the unnecessary new entry.
-	 */
-	if (ret == -EEXIST)
 		new_mpath = mpath;
+	}
+
 	sdata->u.mesh.mesh_paths_generation++;
 	return new_mpath;
 }
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH] rhashtable: Remove obsolete rhashtable_walk_init function

[Herbert Xu]

Here is another patch on top the fixes to mac80211 to finally
remove the obsolete rhashtable_walk_init API.

---8<---
The rhashtable_walk_init function has been obsolete for more than
two years.  This patch finally converts its last users over to
rhashtable_walk_enter and removes it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 20f9c6af7473..ae9c0f71f311 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -1113,14 +1113,6 @@ static inline int rhashtable_replace_fast(
 	return err;
 }
 
-/* Obsolete function, do not use in new code. */
-static inline int rhashtable_walk_init(struct rhashtable *ht,
-				       struct rhashtable_iter *iter, gfp_t gfp)
-{
-	rhashtable_walk_enter(ht, iter);
-	return 0;
-}
-
 /**
  * rhltable_walk_enter - Initialise an iterator
  * @hlt:	Table to walk over
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 852ffa5160f1..0a105d4af166 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -682,7 +682,7 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
  * rhashtable_walk_exit - Free an iterator
  * @iter:	Hash table Iterator
  *
- * This function frees resources allocated by rhashtable_walk_init.
+ * This function frees resources allocated by rhashtable_walk_enter.
  */
 void rhashtable_walk_exit(struct rhashtable_iter *iter)
 {
diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 6a8ac7626797..d96962eea942 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -177,16 +177,11 @@ static int __init test_rht_lookup(struct rhashtable *ht, struct test_obj *array,
 
 static void test_bucket_stats(struct rhashtable *ht, unsigned int entries)
 {
-	unsigned int err, total = 0, chain_len = 0;
+	unsigned int total = 0, chain_len = 0;
 	struct rhashtable_iter hti;
 	struct rhash_head *pos;
 
-	err = rhashtable_walk_init(ht, &hti, GFP_KERNEL);
-	if (err) {
-		pr_warn("Test failed: allocation error");
-		return;
-	}
-
+	rhashtable_walk_enter(ht, &hti);
 	rhashtable_walk_start(&hti);
 
 	while ((pos = rhashtable_walk_next(&hti))) {
diff --git a/net/ipv6/ila/ila_xlat.c b/net/ipv6/ila/ila_xlat.c
index 17c455ff69ff..ae6cd4cef8db 100644
--- a/net/ipv6/ila/ila_xlat.c
+++ b/net/ipv6/ila/ila_xlat.c
@@ -385,10 +385,7 @@ int ila_xlat_nl_cmd_flush(struct sk_buff *skb, struct genl_info *info)
 	spinlock_t *lock;
 	int ret;
 
-	ret = rhashtable_walk_init(&ilan->xlat.rhash_table, &iter, GFP_KERNEL);
-	if (ret)
-		goto done;
-
+	rhashtable_walk_enter(&ilan->xlat.rhash_table, &iter);
 	rhashtable_walk_start(&iter);
 
 	for (;;) {
@@ -509,23 +506,17 @@ int ila_xlat_nl_dump_start(struct netlink_callback *cb)
 	struct net *net = sock_net(cb->skb->sk);
 	struct ila_net *ilan = net_generic(net, ila_net_id);
 	struct ila_dump_iter *iter;
-	int ret;
 
 	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter)
 		return -ENOMEM;
 
-	ret = rhashtable_walk_init(&ilan->xlat.rhash_table, &iter->rhiter,
-				   GFP_KERNEL);
-	if (ret) {
-		kfree(iter);
-		return ret;
-	}
+	rhashtable_walk_enter(&ilan->xlat.rhash_table, &iter->rhiter);
 
 	iter->skip = 0;
 	cb->args[0] = (long)iter;
 
-	return ret;
+	return 0;
 }
 
 int ila_xlat_nl_dump_done(struct netlink_callback *cb)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 3c023d6120f6..f369cc751cea 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2541,15 +2541,7 @@ struct nl_seq_iter {
 
 static int netlink_walk_start(struct nl_seq_iter *iter)
 {
-	int err;
-
-	err = rhashtable_walk_init(&nl_table[iter->link].hash, &iter->hti,
-				   GFP_KERNEL);
-	if (err) {
-		iter->link = MAX_LINKS;
-		return err;
-	}
-
+	rhashtable_walk_enter(&nl_table[iter->link].hash, &iter->hti);
 	rhashtable_walk_start(&iter->hti);
 
 	return 0;
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] rhashtable: Remove obsolete rhashtable_walk_init function

[Herbert Xu]

On Wed, Feb 13, 2019 at 07:20:51PM +0800, kbuild test robot wrote:
> Hi Herbert,
> 
> I love your patch! Yet something to improve:
> 
> [auto build test ERROR on linus/master]
> [also build test ERROR on v5.0-rc4 next-20190212]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Herbert-Xu/rhashtable-Remove-obsolete-rhashtable_walk_init-function/20190213-182336
> config: x86_64-lkp (attached as .config)
> compiler: gcc-8 (Debian 8.2.0-20) 8.2.0
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> All errors (new ones prefixed by >>):
> 
>    net/mac80211/mesh_pathtbl.c: In function '__mesh_path_lookup_by_idx':
> >> net/mac80211/mesh_pathtbl.c:256:8: error: implicit declaration of function 'rhashtable_walk_init'; did you mean 'rhashtable_walk_exit'? [-Werror=implicit-function-declaration]
>      ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
>            ^~~~~~~~~~~~~~~~~~~~
>            rhashtable_walk_exit
>    cc1: some warnings being treated as errors

This patch depends on a prior patch to mac80211.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[v2 PATCH 0/4] mac80211: Fix incorrect usage of rhashtable walk API

[Herbert Xu]

Hi:

The first two patches in this series are bug fixes and should be
backported to stable.

They fixes a number of issues with the use of the rhashtable API
in mac80211.  First of all it converts the use of rashtable walks over
to a simple linked list.  This is because an rhashtable walk is
inherently unstable and not meant for uses that require stability,
e.g., when you're trying to lookup an object to delete.

It also fixes a potential memory leak when the rhashtable insertion
fails (which can occur due to OOM).

The third patch is a code-cleanup to mac80211 while the last patch
removes an obsolete rhashtable API.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH 1/4] mac80211: Use linked list instead of rhashtable walk for mesh tables

[Herbert Xu]

The mesh table code walks over hash tables for two purposes.  First of
all it's used as part of a netlink dump process, but it is also used
for looking up entries to delete using criteria other than the hash
key.

The second purpose is directly contrary to the design specification
of rhashtable walks.  It is only meant for use by netlink dumps.

This is because rhashtable is resizable and you cannot obtain a
stable walk over it during a resize process.

In fact mesh's use of rhashtable for dumping is bogus too.  Rather
than using rhashtable walk's iterator to keep track of the current
position, it always converts the current position to an integer
which defeats the purpose of the iterator.

Therefore this patch converts all uses of rhashtable walk into a
simple linked list.

This patch also adds a new spin lock to protect the hash table
insertion/removal as well as the walk list modifications.  In fact
the previous code was buggy as the removals can race with each
other, potentially resulting in a double-free.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh.h         |    6 +
 net/mac80211/mesh_pathtbl.c |  138 +++++++++++---------------------------------
 2 files changed, 43 insertions(+), 101 deletions(-)

diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index cad6592c52a1..2ec7011a4d07 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -70,6 +70,7 @@ enum mesh_deferred_task_flags {
  * @dst: mesh path destination mac address
  * @mpp: mesh proxy mac address
  * @rhash: rhashtable list pointer
+ * @walk_list: linked list containing all mesh_path objects.
  * @gate_list: list pointer for known gates list
  * @sdata: mesh subif
  * @next_hop: mesh neighbor to which frames for this destination will be
@@ -105,6 +106,7 @@ struct mesh_path {
 	u8 dst[ETH_ALEN];
 	u8 mpp[ETH_ALEN];	/* used for MPP or MAP */
 	struct rhash_head rhash;
+	struct hlist_node walk_list;
 	struct hlist_node gate_list;
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info __rcu *next_hop;
@@ -133,12 +135,16 @@ struct mesh_path {
  * gate's mpath may or may not be resolved and active.
  * @gates_lock: protects updates to known_gates
  * @rhead: the rhashtable containing struct mesh_paths, keyed by dest addr
+ * @walk_head: linked list containging all mesh_path objects
+ * @walk_lock: lock protecting walk_head
  * @entries: number of entries in the table
  */
 struct mesh_table {
 	struct hlist_head known_gates;
 	spinlock_t gates_lock;
 	struct rhashtable rhead;
+	struct hlist_head walk_head;
+	spinlock_t walk_lock;
 	atomic_t entries;		/* Up to MAX_MESH_NEIGHBOURS */
 };
 
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index a5125624a76d..884a0d212e8b 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -59,8 +59,10 @@ static struct mesh_table *mesh_table_alloc(void)
 		return NULL;
 
 	INIT_HLIST_HEAD(&newtbl->known_gates);
+	INIT_HLIST_HEAD(&newtbl->walk_head);
 	atomic_set(&newtbl->entries,  0);
 	spin_lock_init(&newtbl->gates_lock);
+	spin_lock_init(&newtbl->walk_lock);
 
 	return newtbl;
 }
@@ -249,28 +251,15 @@ mpp_path_lookup(struct ieee80211_sub_if_data *sdata, const u8 *dst)
 static struct mesh_path *
 __mesh_path_lookup_by_idx(struct mesh_table *tbl, int idx)
 {
-	int i = 0, ret;
-	struct mesh_path *mpath = NULL;
-	struct rhashtable_iter iter;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return NULL;
-
-	rhashtable_walk_start(&iter);
+	int i = 0;
+	struct mesh_path *mpath;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	hlist_for_each_entry_rcu(mpath, &tbl->walk_head, walk_list) {
 		if (i++ == idx)
 			break;
 	}
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 
-	if (IS_ERR(mpath) || !mpath)
+	if (!mpath)
 		return NULL;
 
 	if (mpath_expired(mpath)) {
@@ -432,6 +421,7 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 		return ERR_PTR(-ENOMEM);
 
 	tbl = sdata->u.mesh.mesh_paths;
+	spin_lock_bh(&tbl->walk_lock);
 	do {
 		ret = rhashtable_lookup_insert_fast(&tbl->rhead,
 						    &new_mpath->rhash,
@@ -441,8 +431,10 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 			mpath = rhashtable_lookup_fast(&tbl->rhead,
 						       dst,
 						       mesh_rht_params);
-
+		else if (!ret)
+			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 	} while (unlikely(ret == -EEXIST && !mpath));
+	spin_unlock_bh(&tbl->walk_lock);
 
 	if (ret && ret != -EEXIST)
 		return ERR_PTR(ret);
@@ -480,9 +472,14 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata,
 
 	memcpy(new_mpath->mpp, mpp, ETH_ALEN);
 	tbl = sdata->u.mesh.mpp_paths;
+
+	spin_lock_bh(&tbl->walk_lock);
 	ret = rhashtable_lookup_insert_fast(&tbl->rhead,
 					    &new_mpath->rhash,
 					    mesh_rht_params);
+	if (!ret)
+		hlist_add_head_rcu(&new_mpath->walk_list, &tbl->walk_head);
+	spin_unlock_bh(&tbl->walk_lock);
 
 	sdata->u.mesh.mpp_paths_generation++;
 	return ret;
@@ -503,20 +500,9 @@ void mesh_plink_broken(struct sta_info *sta)
 	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
 	static const u8 bcast[ETH_ALEN] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(mpath, &tbl->walk_head, walk_list) {
 		if (rcu_access_pointer(mpath->next_hop) == sta &&
 		    mpath->flags & MESH_PATH_ACTIVE &&
 		    !(mpath->flags & MESH_PATH_FIXED)) {
@@ -530,8 +516,7 @@ void mesh_plink_broken(struct sta_info *sta)
 				WLAN_REASON_MESH_PATH_DEST_UNREACHABLE, bcast);
 		}
 	}
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	rcu_read_unlock();
 }
 
 static void mesh_path_free_rcu(struct mesh_table *tbl,
@@ -551,6 +536,7 @@ static void mesh_path_free_rcu(struct mesh_table *tbl,
 
 static void __mesh_path_del(struct mesh_table *tbl, struct mesh_path *mpath)
 {
+	hlist_del_rcu(&mpath->walk_list);
 	rhashtable_remove_fast(&tbl->rhead, &mpath->rhash, mesh_rht_params);
 	mesh_path_free_rcu(tbl, mpath);
 }
@@ -571,27 +557,14 @@ void mesh_path_flush_by_nexthop(struct sta_info *sta)
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	struct hlist_node *n;
 
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if (rcu_access_pointer(mpath->next_hop) == sta)
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
@@ -599,51 +572,26 @@ static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
 {
 	struct mesh_table *tbl = sdata->u.mesh.mpp_paths;
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	struct hlist_node *n;
 
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if (ether_addr_equal(mpath->mpp, proxy))
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 static void table_flush_by_iface(struct mesh_table *tbl)
 {
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
+	struct hlist_node *n;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 /**
@@ -675,7 +623,7 @@ static int table_path_del(struct mesh_table *tbl,
 {
 	struct mesh_path *mpath;
 
-	rcu_read_lock();
+	spin_lock_bh(&tbl->walk_lock);
 	mpath = rhashtable_lookup_fast(&tbl->rhead, addr, mesh_rht_params);
 	if (!mpath) {
 		rcu_read_unlock();
@@ -683,7 +631,7 @@ static int table_path_del(struct mesh_table *tbl,
 	}
 
 	__mesh_path_del(tbl, mpath);
-	rcu_read_unlock();
+	spin_unlock_bh(&tbl->walk_lock);
 	return 0;
 }
 
@@ -854,28 +802,16 @@ void mesh_path_tbl_expire(struct ieee80211_sub_if_data *sdata,
 			  struct mesh_table *tbl)
 {
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
+	struct hlist_node *n;
 
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_KERNEL);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
 		    (!(mpath->flags & MESH_PATH_FIXED)) &&
 		     time_after(jiffies, mpath->exp_time + MESH_PATH_EXPIRE))
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 void mesh_path_expire(struct ieee80211_sub_if_data *sdata)

[PATCH 2/4] mac80211: Free mpath object when rhashtable insertion fails

[Herbert Xu]

When rhashtable insertion fails the mesh table code doesn't free
the now-orphan mesh path object.  This patch fixes that.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh_pathtbl.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 884a0d212e8b..db5a1aef22db 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -436,17 +436,18 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 	} while (unlikely(ret == -EEXIST && !mpath));
 	spin_unlock_bh(&tbl->walk_lock);
 
-	if (ret && ret != -EEXIST)
+	if (ret)
+		kfree(new_mpath);
+
+	if (ret != -EEXIST)
 		return ERR_PTR(ret);
 
 	/* At this point either new_mpath was added, or we found a
 	 * matching entry already in the table; in the latter case
 	 * free the unnecessary new entry.
 	 */
-	if (ret == -EEXIST) {
-		kfree(new_mpath);
+	if (ret == -EEXIST)
 		new_mpath = mpath;
-	}
 	sdata->u.mesh.mesh_paths_generation++;
 	return new_mpath;
 }
@@ -481,6 +482,9 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata,
 		hlist_add_head_rcu(&new_mpath->walk_list, &tbl->walk_head);
 	spin_unlock_bh(&tbl->walk_lock);
 
+	if (ret)
+		kfree(new_mpath);
+
 	sdata->u.mesh.mpp_paths_generation++;
 	return ret;
 }

Re: [PATCH 2/4] mac80211: Free mpath object when rhashtable insertion fails

[Johannes Berg]

On Wed, 2019-02-13 at 22:39 +0800, Herbert Xu wrote:
> +	if (ret != -EEXIST)
>  		return ERR_PTR(ret);

Surely that should still be "if (ret && ret != -EEXIST)" otherwise you
return for the success case too? or "else if"?

I'd probably say we should combine all those ifs into something like this?


if (ret == 0) {
	sdata->u.mesh.mesh_paths_generation++;
	return new_mpath;
} else if (ret == -EEXIST) {
	kfree(new_mpath);
	return mpath;
} else {
	kfree(new_mpath);
	return NULL;
}


Yes, that's a small change in behaviour as to when the generation
counter is updated, but I'm pretty sure it really only needs updating
when we inserted something, not if we found an old mpath.

johannes

Re: [PATCH 2/4] mac80211: Free mpath object when rhashtable insertion fails

[Herbert Xu]

On Wed, Feb 13, 2019 at 04:04:29PM +0100, Johannes Berg wrote:
> On Wed, 2019-02-13 at 22:39 +0800, Herbert Xu wrote:
> > +	if (ret != -EEXIST)
> >  		return ERR_PTR(ret);
> 
> Surely that should still be "if (ret && ret != -EEXIST)" otherwise you
> return for the success case too? or "else if"?
> 
> I'd probably say we should combine all those ifs into something like this?
> 
> 
> if (ret == 0) {
> 	sdata->u.mesh.mesh_paths_generation++;
> 	return new_mpath;
> } else if (ret == -EEXIST) {
> 	kfree(new_mpath);
> 	return mpath;
> } else {
> 	kfree(new_mpath);
> 	return NULL;
> }
> 
> 
> Yes, that's a small change in behaviour as to when the generation
> counter is updated, but I'm pretty sure it really only needs updating
> when we inserted something, not if we found an old mpath.

You are right.  Let me fix this and repost.

Thanks!
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 2/4] mac80211: Free mpath object when rhashtable insertion fails

[Herbert Xu]

On Wed, Feb 13, 2019 at 04:04:29PM +0100, Johannes Berg wrote:
>
> Yes, that's a small change in behaviour as to when the generation
> counter is updated, but I'm pretty sure it really only needs updating
> when we inserted something, not if we found an old mpath.

I decided not to do this in my patch as it's not directly related
to the kfree issue.

But I agree that this makes more sense and we should make that
change in another patch.

Thanks!
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH 3/4] mac80211: Use rhashtable_lookup_get_insert_fast instead of racy code

[Herbert Xu]

The code in mesh_path_add tries to handle the case where a duplicate
entry is added to the rhashtable by doing a lookup after a failed
insertion.  It also tries to handle races by repeating the insertion
should the lookup fail.

This is now unnecessary as we have rhashtable API functions that can
directly return the mathcing object.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh_pathtbl.c |   31 ++++++++++---------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index db5a1aef22db..8902395e406e 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -404,7 +404,6 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 {
 	struct mesh_table *tbl;
 	struct mesh_path *mpath, *new_mpath;
-	int ret;
 
 	if (ether_addr_equal(dst, sdata->vif.addr))
 		/* never add ourselves as neighbours */
@@ -422,32 +421,22 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 
 	tbl = sdata->u.mesh.mesh_paths;
 	spin_lock_bh(&tbl->walk_lock);
-	do {
-		ret = rhashtable_lookup_insert_fast(&tbl->rhead,
-						    &new_mpath->rhash,
-						    mesh_rht_params);
-
-		if (ret == -EEXIST)
-			mpath = rhashtable_lookup_fast(&tbl->rhead,
-						       dst,
-						       mesh_rht_params);
-		else if (!ret)
-			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
-	} while (unlikely(ret == -EEXIST && !mpath));
+	mpath = rhashtable_lookup_get_insert_fast(&tbl->rhead,
+						  &new_mpath->rhash,
+						  mesh_rht_params);
+	if (!mpath)
+		hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 	spin_unlock_bh(&tbl->walk_lock);
 
-	if (ret)
+	if (mpath) {
 		kfree(new_mpath);
 
-	if (ret != -EEXIST)
-		return ERR_PTR(ret);
+		if (IS_ERR(mpath))
+			return mpath;
 
-	/* At this point either new_mpath was added, or we found a
-	 * matching entry already in the table; in the latter case
-	 * free the unnecessary new entry.
-	 */
-	if (ret == -EEXIST)
 		new_mpath = mpath;
+	}
+
 	sdata->u.mesh.mesh_paths_generation++;
 	return new_mpath;
 }

[PATCH 4/4] rhashtable: Remove obsolete rhashtable_walk_init function

[Herbert Xu]

The rhashtable_walk_init function has been obsolete for more than
two years.  This patch finally converts its last users over to
rhashtable_walk_enter and removes it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 include/linux/rhashtable.h |    8 --------
 lib/rhashtable.c           |    2 +-
 lib/test_rhashtable.c      |    9 ++-------
 net/ipv6/ila/ila_xlat.c    |   15 +++------------
 net/netlink/af_netlink.c   |   10 +---------
 5 files changed, 7 insertions(+), 37 deletions(-)

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 20f9c6af7473..ae9c0f71f311 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -1113,14 +1113,6 @@ static inline int rhashtable_replace_fast(
 	return err;
 }
 
-/* Obsolete function, do not use in new code. */
-static inline int rhashtable_walk_init(struct rhashtable *ht,
-				       struct rhashtable_iter *iter, gfp_t gfp)
-{
-	rhashtable_walk_enter(ht, iter);
-	return 0;
-}
-
 /**
  * rhltable_walk_enter - Initialise an iterator
  * @hlt:	Table to walk over
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 852ffa5160f1..0a105d4af166 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -682,7 +682,7 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
  * rhashtable_walk_exit - Free an iterator
  * @iter:	Hash table Iterator
  *
- * This function frees resources allocated by rhashtable_walk_init.
+ * This function frees resources allocated by rhashtable_walk_enter.
  */
 void rhashtable_walk_exit(struct rhashtable_iter *iter)
 {
diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 6a8ac7626797..d96962eea942 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -177,16 +177,11 @@ static int __init test_rht_lookup(struct rhashtable *ht, struct test_obj *array,
 
 static void test_bucket_stats(struct rhashtable *ht, unsigned int entries)
 {
-	unsigned int err, total = 0, chain_len = 0;
+	unsigned int total = 0, chain_len = 0;
 	struct rhashtable_iter hti;
 	struct rhash_head *pos;
 
-	err = rhashtable_walk_init(ht, &hti, GFP_KERNEL);
-	if (err) {
-		pr_warn("Test failed: allocation error");
-		return;
-	}
-
+	rhashtable_walk_enter(ht, &hti);
 	rhashtable_walk_start(&hti);
 
 	while ((pos = rhashtable_walk_next(&hti))) {
diff --git a/net/ipv6/ila/ila_xlat.c b/net/ipv6/ila/ila_xlat.c
index 17c455ff69ff..ae6cd4cef8db 100644
--- a/net/ipv6/ila/ila_xlat.c
+++ b/net/ipv6/ila/ila_xlat.c
@@ -385,10 +385,7 @@ int ila_xlat_nl_cmd_flush(struct sk_buff *skb, struct genl_info *info)
 	spinlock_t *lock;
 	int ret;
 
-	ret = rhashtable_walk_init(&ilan->xlat.rhash_table, &iter, GFP_KERNEL);
-	if (ret)
-		goto done;
-
+	rhashtable_walk_enter(&ilan->xlat.rhash_table, &iter);
 	rhashtable_walk_start(&iter);
 
 	for (;;) {
@@ -509,23 +506,17 @@ int ila_xlat_nl_dump_start(struct netlink_callback *cb)
 	struct net *net = sock_net(cb->skb->sk);
 	struct ila_net *ilan = net_generic(net, ila_net_id);
 	struct ila_dump_iter *iter;
-	int ret;
 
 	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter)
 		return -ENOMEM;
 
-	ret = rhashtable_walk_init(&ilan->xlat.rhash_table, &iter->rhiter,
-				   GFP_KERNEL);
-	if (ret) {
-		kfree(iter);
-		return ret;
-	}
+	rhashtable_walk_enter(&ilan->xlat.rhash_table, &iter->rhiter);
 
 	iter->skip = 0;
 	cb->args[0] = (long)iter;
 
-	return ret;
+	return 0;
 }
 
 int ila_xlat_nl_dump_done(struct netlink_callback *cb)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 3c023d6120f6..f369cc751cea 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2541,15 +2541,7 @@ struct nl_seq_iter {
 
 static int netlink_walk_start(struct nl_seq_iter *iter)
 {
-	int err;
-
-	err = rhashtable_walk_init(&nl_table[iter->link].hash, &iter->hti,
-				   GFP_KERNEL);
-	if (err) {
-		iter->link = MAX_LINKS;
-		return err;
-	}
-
+	rhashtable_walk_enter(&nl_table[iter->link].hash, &iter->hti);
 	rhashtable_walk_start(&iter->hti);
 
 	return 0;

Re: [v2 PATCH 0/4] mac80211: Fix incorrect usage of rhashtable walk API

[Johannes Berg]

On Wed, 2019-02-13 at 22:38 +0800, Herbert Xu wrote:
> Hi:
> 
> The first two patches in this series are bug fixes and should be
> backported to stable.
> 
> They fixes a number of issues with the use of the rhashtable API
> in mac80211.  First of all it converts the use of rashtable walks over
> to a simple linked list.  This is because an rhashtable walk is
> inherently unstable and not meant for uses that require stability,
> e.g., when you're trying to lookup an object to delete.
> 
> It also fixes a potential memory leak when the rhashtable insertion
> fails (which can occur due to OOM).

Thanks a lot Herbert! That looks simpler than I thought it would be.

johannes

[v3 PATCH 0/4] mac80211: Fix incorrect usage of rhashtable walk API

[Herbert Xu]

Hi:

v3 fixes a bug in patch two where we would return a NULL pointer
when we should return an existing path.

The first two patches in this series are bug fixes and should be
backported to stable.

They fixes a number of issues with the use of the rhashtable API
in mac80211.  First of all it converts the use of rashtable walks over
to a simple linked list.  This is because an rhashtable walk is
inherently unstable and not meant for uses that require stability,
e.g., when you're trying to lookup an object to delete.

It also fixes a potential memory leak when the rhashtable insertion
fails (which can occur due to OOM).

The third patch is a code-cleanup to mac80211 while the last patch
removes an obsolete rhashtable API.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH 1/4] mac80211: Use linked list instead of rhashtable walk for mesh tables

[Herbert Xu]

The mesh table code walks over hash tables for two purposes.  First of
all it's used as part of a netlink dump process, but it is also used
for looking up entries to delete using criteria other than the hash
key.

The second purpose is directly contrary to the design specification
of rhashtable walks.  It is only meant for use by netlink dumps.

This is because rhashtable is resizable and you cannot obtain a
stable walk over it during a resize process.

In fact mesh's use of rhashtable for dumping is bogus too.  Rather
than using rhashtable walk's iterator to keep track of the current
position, it always converts the current position to an integer
which defeats the purpose of the iterator.

Therefore this patch converts all uses of rhashtable walk into a
simple linked list.

This patch also adds a new spin lock to protect the hash table
insertion/removal as well as the walk list modifications.  In fact
the previous code was buggy as the removals can race with each
other, potentially resulting in a double-free.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh.h         |    6 +
 net/mac80211/mesh_pathtbl.c |  138 +++++++++++---------------------------------
 2 files changed, 43 insertions(+), 101 deletions(-)

diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index cad6592c52a1..2ec7011a4d07 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -70,6 +70,7 @@ enum mesh_deferred_task_flags {
  * @dst: mesh path destination mac address
  * @mpp: mesh proxy mac address
  * @rhash: rhashtable list pointer
+ * @walk_list: linked list containing all mesh_path objects.
  * @gate_list: list pointer for known gates list
  * @sdata: mesh subif
  * @next_hop: mesh neighbor to which frames for this destination will be
@@ -105,6 +106,7 @@ struct mesh_path {
 	u8 dst[ETH_ALEN];
 	u8 mpp[ETH_ALEN];	/* used for MPP or MAP */
 	struct rhash_head rhash;
+	struct hlist_node walk_list;
 	struct hlist_node gate_list;
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info __rcu *next_hop;
@@ -133,12 +135,16 @@ struct mesh_path {
  * gate's mpath may or may not be resolved and active.
  * @gates_lock: protects updates to known_gates
  * @rhead: the rhashtable containing struct mesh_paths, keyed by dest addr
+ * @walk_head: linked list containging all mesh_path objects
+ * @walk_lock: lock protecting walk_head
  * @entries: number of entries in the table
  */
 struct mesh_table {
 	struct hlist_head known_gates;
 	spinlock_t gates_lock;
 	struct rhashtable rhead;
+	struct hlist_head walk_head;
+	spinlock_t walk_lock;
 	atomic_t entries;		/* Up to MAX_MESH_NEIGHBOURS */
 };
 
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index a5125624a76d..884a0d212e8b 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -59,8 +59,10 @@ static struct mesh_table *mesh_table_alloc(void)
 		return NULL;
 
 	INIT_HLIST_HEAD(&newtbl->known_gates);
+	INIT_HLIST_HEAD(&newtbl->walk_head);
 	atomic_set(&newtbl->entries,  0);
 	spin_lock_init(&newtbl->gates_lock);
+	spin_lock_init(&newtbl->walk_lock);
 
 	return newtbl;
 }
@@ -249,28 +251,15 @@ mpp_path_lookup(struct ieee80211_sub_if_data *sdata, const u8 *dst)
 static struct mesh_path *
 __mesh_path_lookup_by_idx(struct mesh_table *tbl, int idx)
 {
-	int i = 0, ret;
-	struct mesh_path *mpath = NULL;
-	struct rhashtable_iter iter;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return NULL;
-
-	rhashtable_walk_start(&iter);
+	int i = 0;
+	struct mesh_path *mpath;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	hlist_for_each_entry_rcu(mpath, &tbl->walk_head, walk_list) {
 		if (i++ == idx)
 			break;
 	}
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
 
-	if (IS_ERR(mpath) || !mpath)
+	if (!mpath)
 		return NULL;
 
 	if (mpath_expired(mpath)) {
@@ -432,6 +421,7 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 		return ERR_PTR(-ENOMEM);
 
 	tbl = sdata->u.mesh.mesh_paths;
+	spin_lock_bh(&tbl->walk_lock);
 	do {
 		ret = rhashtable_lookup_insert_fast(&tbl->rhead,
 						    &new_mpath->rhash,
@@ -441,8 +431,10 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 			mpath = rhashtable_lookup_fast(&tbl->rhead,
 						       dst,
 						       mesh_rht_params);
-
+		else if (!ret)
+			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 	} while (unlikely(ret == -EEXIST && !mpath));
+	spin_unlock_bh(&tbl->walk_lock);
 
 	if (ret && ret != -EEXIST)
 		return ERR_PTR(ret);
@@ -480,9 +472,14 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata,
 
 	memcpy(new_mpath->mpp, mpp, ETH_ALEN);
 	tbl = sdata->u.mesh.mpp_paths;
+
+	spin_lock_bh(&tbl->walk_lock);
 	ret = rhashtable_lookup_insert_fast(&tbl->rhead,
 					    &new_mpath->rhash,
 					    mesh_rht_params);
+	if (!ret)
+		hlist_add_head_rcu(&new_mpath->walk_list, &tbl->walk_head);
+	spin_unlock_bh(&tbl->walk_lock);
 
 	sdata->u.mesh.mpp_paths_generation++;
 	return ret;
@@ -503,20 +500,9 @@ void mesh_plink_broken(struct sta_info *sta)
 	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
 	static const u8 bcast[ETH_ALEN] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(mpath, &tbl->walk_head, walk_list) {
 		if (rcu_access_pointer(mpath->next_hop) == sta &&
 		    mpath->flags & MESH_PATH_ACTIVE &&
 		    !(mpath->flags & MESH_PATH_FIXED)) {
@@ -530,8 +516,7 @@ void mesh_plink_broken(struct sta_info *sta)
 				WLAN_REASON_MESH_PATH_DEST_UNREACHABLE, bcast);
 		}
 	}
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	rcu_read_unlock();
 }
 
 static void mesh_path_free_rcu(struct mesh_table *tbl,
@@ -551,6 +536,7 @@ static void mesh_path_free_rcu(struct mesh_table *tbl,
 
 static void __mesh_path_del(struct mesh_table *tbl, struct mesh_path *mpath)
 {
+	hlist_del_rcu(&mpath->walk_list);
 	rhashtable_remove_fast(&tbl->rhead, &mpath->rhash, mesh_rht_params);
 	mesh_path_free_rcu(tbl, mpath);
 }
@@ -571,27 +557,14 @@ void mesh_path_flush_by_nexthop(struct sta_info *sta)
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	struct hlist_node *n;
 
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if (rcu_access_pointer(mpath->next_hop) == sta)
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
@@ -599,51 +572,26 @@ static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
 {
 	struct mesh_table *tbl = sdata->u.mesh.mpp_paths;
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	struct hlist_node *n;
 
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if (ether_addr_equal(mpath->mpp, proxy))
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 static void table_flush_by_iface(struct mesh_table *tbl)
 {
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
-
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_ATOMIC);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
+	struct hlist_node *n;
 
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 /**
@@ -675,7 +623,7 @@ static int table_path_del(struct mesh_table *tbl,
 {
 	struct mesh_path *mpath;
 
-	rcu_read_lock();
+	spin_lock_bh(&tbl->walk_lock);
 	mpath = rhashtable_lookup_fast(&tbl->rhead, addr, mesh_rht_params);
 	if (!mpath) {
 		rcu_read_unlock();
@@ -683,7 +631,7 @@ static int table_path_del(struct mesh_table *tbl,
 	}
 
 	__mesh_path_del(tbl, mpath);
-	rcu_read_unlock();
+	spin_unlock_bh(&tbl->walk_lock);
 	return 0;
 }
 
@@ -854,28 +802,16 @@ void mesh_path_tbl_expire(struct ieee80211_sub_if_data *sdata,
 			  struct mesh_table *tbl)
 {
 	struct mesh_path *mpath;
-	struct rhashtable_iter iter;
-	int ret;
+	struct hlist_node *n;
 
-	ret = rhashtable_walk_init(&tbl->rhead, &iter, GFP_KERNEL);
-	if (ret)
-		return;
-
-	rhashtable_walk_start(&iter);
-
-	while ((mpath = rhashtable_walk_next(&iter))) {
-		if (IS_ERR(mpath) && PTR_ERR(mpath) == -EAGAIN)
-			continue;
-		if (IS_ERR(mpath))
-			break;
+	spin_lock_bh(&tbl->walk_lock);
+	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
 		if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
 		    (!(mpath->flags & MESH_PATH_FIXED)) &&
 		     time_after(jiffies, mpath->exp_time + MESH_PATH_EXPIRE))
 			__mesh_path_del(tbl, mpath);
 	}
-
-	rhashtable_walk_stop(&iter);
-	rhashtable_walk_exit(&iter);
+	spin_unlock_bh(&tbl->walk_lock);
 }
 
 void mesh_path_expire(struct ieee80211_sub_if_data *sdata)

[PATCH 2/4] mac80211: Free mpath object when rhashtable insertion fails

[Herbert Xu]

When rhashtable insertion fails the mesh table code doesn't free
the now-orphan mesh path object.  This patch fixes that.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh_pathtbl.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 884a0d212e8b..c3a7396fb955 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -436,17 +436,15 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 	} while (unlikely(ret == -EEXIST && !mpath));
 	spin_unlock_bh(&tbl->walk_lock);
 
-	if (ret && ret != -EEXIST)
-		return ERR_PTR(ret);
-
-	/* At this point either new_mpath was added, or we found a
-	 * matching entry already in the table; in the latter case
-	 * free the unnecessary new entry.
-	 */
-	if (ret == -EEXIST) {
+	if (ret) {
 		kfree(new_mpath);
+
+		if (ret != -EEXIST)
+			return ERR_PTR(ret);
+
 		new_mpath = mpath;
 	}
+
 	sdata->u.mesh.mesh_paths_generation++;
 	return new_mpath;
 }
@@ -481,6 +479,9 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata,
 		hlist_add_head_rcu(&new_mpath->walk_list, &tbl->walk_head);
 	spin_unlock_bh(&tbl->walk_lock);
 
+	if (ret)
+		kfree(new_mpath);
+
 	sdata->u.mesh.mpp_paths_generation++;
 	return ret;
 }

[PATCH 3/4] mac80211: Use rhashtable_lookup_get_insert_fast instead of racy code

[Herbert Xu]

The code in mesh_path_add tries to handle the case where a duplicate
entry is added to the rhashtable by doing a lookup after a failed
insertion.  It also tries to handle races by repeating the insertion
should the lookup fail.

This is now unnecessary as we have rhashtable API functions that can
directly return the mathcing object.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 net/mac80211/mesh_pathtbl.c |   24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index c3a7396fb955..8902395e406e 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -404,7 +404,6 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 {
 	struct mesh_table *tbl;
 	struct mesh_path *mpath, *new_mpath;
-	int ret;
 
 	if (ether_addr_equal(dst, sdata->vif.addr))
 		/* never add ourselves as neighbours */
@@ -422,25 +421,18 @@ struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
 
 	tbl = sdata->u.mesh.mesh_paths;
 	spin_lock_bh(&tbl->walk_lock);
-	do {
-		ret = rhashtable_lookup_insert_fast(&tbl->rhead,
-						    &new_mpath->rhash,
-						    mesh_rht_params);
-
-		if (ret == -EEXIST)
-			mpath = rhashtable_lookup_fast(&tbl->rhead,
-						       dst,
-						       mesh_rht_params);
-		else if (!ret)
-			hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
-	} while (unlikely(ret == -EEXIST && !mpath));
+	mpath = rhashtable_lookup_get_insert_fast(&tbl->rhead,
+						  &new_mpath->rhash,
+						  mesh_rht_params);
+	if (!mpath)
+		hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
 	spin_unlock_bh(&tbl->walk_lock);
 
-	if (ret) {
+	if (mpath) {
 		kfree(new_mpath);
 
-		if (ret != -EEXIST)
-			return ERR_PTR(ret);
+		if (IS_ERR(mpath))
+			return mpath;
 
 		new_mpath = mpath;
 	}

[PATCH 4/4] rhashtable: Remove obsolete rhashtable_walk_init function

[Herbert Xu]

The rhashtable_walk_init function has been obsolete for more than
two years.  This patch finally converts its last users over to
rhashtable_walk_enter and removes it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 include/linux/rhashtable.h |    8 --------
 lib/rhashtable.c           |    2 +-
 lib/test_rhashtable.c      |    9 ++-------
 net/ipv6/ila/ila_xlat.c    |   15 +++------------
 net/netlink/af_netlink.c   |   10 +---------
 5 files changed, 7 insertions(+), 37 deletions(-)

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 20f9c6af7473..ae9c0f71f311 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -1113,14 +1113,6 @@ static inline int rhashtable_replace_fast(
 	return err;
 }
 
-/* Obsolete function, do not use in new code. */
-static inline int rhashtable_walk_init(struct rhashtable *ht,
-				       struct rhashtable_iter *iter, gfp_t gfp)
-{
-	rhashtable_walk_enter(ht, iter);
-	return 0;
-}
-
 /**
  * rhltable_walk_enter - Initialise an iterator
  * @hlt:	Table to walk over
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 852ffa5160f1..0a105d4af166 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -682,7 +682,7 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
  * rhashtable_walk_exit - Free an iterator
  * @iter:	Hash table Iterator
  *
- * This function frees resources allocated by rhashtable_walk_init.
+ * This function frees resources allocated by rhashtable_walk_enter.
  */
 void rhashtable_walk_exit(struct rhashtable_iter *iter)
 {
diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 6a8ac7626797..d96962eea942 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -177,16 +177,11 @@ static int __init test_rht_lookup(struct rhashtable *ht, struct test_obj *array,
 
 static void test_bucket_stats(struct rhashtable *ht, unsigned int entries)
 {
-	unsigned int err, total = 0, chain_len = 0;
+	unsigned int total = 0, chain_len = 0;
 	struct rhashtable_iter hti;
 	struct rhash_head *pos;
 
-	err = rhashtable_walk_init(ht, &hti, GFP_KERNEL);
-	if (err) {
-		pr_warn("Test failed: allocation error");
-		return;
-	}
-
+	rhashtable_walk_enter(ht, &hti);
 	rhashtable_walk_start(&hti);
 
 	while ((pos = rhashtable_walk_next(&hti))) {
diff --git a/net/ipv6/ila/ila_xlat.c b/net/ipv6/ila/ila_xlat.c
index 17c455ff69ff..ae6cd4cef8db 100644
--- a/net/ipv6/ila/ila_xlat.c
+++ b/net/ipv6/ila/ila_xlat.c
@@ -385,10 +385,7 @@ int ila_xlat_nl_cmd_flush(struct sk_buff *skb, struct genl_info *info)
 	spinlock_t *lock;
 	int ret;
 
-	ret = rhashtable_walk_init(&ilan->xlat.rhash_table, &iter, GFP_KERNEL);
-	if (ret)
-		goto done;
-
+	rhashtable_walk_enter(&ilan->xlat.rhash_table, &iter);
 	rhashtable_walk_start(&iter);
 
 	for (;;) {
@@ -509,23 +506,17 @@ int ila_xlat_nl_dump_start(struct netlink_callback *cb)
 	struct net *net = sock_net(cb->skb->sk);
 	struct ila_net *ilan = net_generic(net, ila_net_id);
 	struct ila_dump_iter *iter;
-	int ret;
 
 	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter)
 		return -ENOMEM;
 
-	ret = rhashtable_walk_init(&ilan->xlat.rhash_table, &iter->rhiter,
-				   GFP_KERNEL);
-	if (ret) {
-		kfree(iter);
-		return ret;
-	}
+	rhashtable_walk_enter(&ilan->xlat.rhash_table, &iter->rhiter);
 
 	iter->skip = 0;
 	cb->args[0] = (long)iter;
 
-	return ret;
+	return 0;
 }
 
 int ila_xlat_nl_dump_done(struct netlink_callback *cb)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 3c023d6120f6..f369cc751cea 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2541,15 +2541,7 @@ struct nl_seq_iter {
 
 static int netlink_walk_start(struct nl_seq_iter *iter)
 {
-	int err;
-
-	err = rhashtable_walk_init(&nl_table[iter->link].hash, &iter->hti,
-				   GFP_KERNEL);
-	if (err) {
-		iter->link = MAX_LINKS;
-		return err;
-	}
-
+	rhashtable_walk_enter(&nl_table[iter->link].hash, &iter->hti);
 	rhashtable_walk_start(&iter->hti);
 
 	return 0;

Re: [v3 PATCH 0/4] mac80211: Fix incorrect usage of rhashtable walk API

[Johannes Berg]

> The first two patches in this series are bug fixes and should be
> backported to stable.
> 
> They fixes a number of issues with the use of the rhashtable API
> in mac80211.  First of all it converts the use of rashtable walks over
> to a simple linked list.  This is because an rhashtable walk is
> inherently unstable and not meant for uses that require stability,
> e.g., when you're trying to lookup an object to delete.

Thanks a lot, Herbert.

Applied those now, I'll send a pull request to Dave with them. Once that
trickles back into net-next I'll apply the third patch (it doesn't apply
without the others), and then Dave you can take the rhashtable one.

Let me know if you'd prefer I take the rhashtable one through my tree,
which really would be only so you don't have to track the dependency.

NB: it'd be easier in patchwork if you tagged all the patches with v3 in
their own PATCH tag, or put the "v3" tag into the actual subject (not
the "[PATCH 0/4]" tag because evidently patchwork drops the tags and
doesn't track them for the *series* just each *patch* ... so with what
you did nothing is visible in patchwork, even just appending "(v3)" to
the subject of the cover letter would've fixed that...

johannes

Re: [v3 PATCH 0/4] mac80211: Fix incorrect usage of rhashtable walk API

[Herbert Xu]

On Fri, Feb 15, 2019 at 01:21:55PM +0100, Johannes Berg wrote:
> 
> Applied those now, I'll send a pull request to Dave with them. Once that
> trickles back into net-next I'll apply the third patch (it doesn't apply
> without the others), and then Dave you can take the rhashtable one.

Thanks Johannes.

> Let me know if you'd prefer I take the rhashtable one through my tree,
> which really would be only so you don't have to track the dependency.

I don't mind.

> NB: it'd be easier in patchwork if you tagged all the patches with v3 in
> their own PATCH tag, or put the "v3" tag into the actual subject (not
> the "[PATCH 0/4]" tag because evidently patchwork drops the tags and
> doesn't track them for the *series* just each *patch* ... so with what
> you did nothing is visible in patchwork, even just appending "(v3)" to
> the subject of the cover letter would've fixed that...

Noted.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt