linux-kernel - [PATCH 4.14 2/9] bpf: fix memory leak in lpm_trie map

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Date:   Fri,  9 Mar 2018 16:19:07 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "ast@...nel.org, daniel@...earbox.net, stable@...r.kernel.org, Yonghong
        Song" <yhs@...com>, Mathieu Malaterre <malat@...ian.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yonghong Song <yhs@...com>
Subject: [PATCH 4.14 2/9] bpf: fix memory leak in lpm_trie map_free callback function

4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Yonghong Song <yhs@...com>

[ upstream commit 9a3efb6b661f71d5675369ace9257833f0e78ef3 ]

There is a memory leak happening in lpm_trie map_free callback
function trie_free. The trie structure itself does not get freed.

Also, trie_free function did not do synchronize_rcu before freeing
various data structures. This is incorrect as some rcu_read_lock
region(s) for lookup, update, delete or get_next_key may not complete yet.
The fix is to add synchronize_rcu in the beginning of trie_free.
The useless spin_lock is removed from this function as well.

Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation")
Reported-by: Mathieu Malaterre <malat@...ian.org>
Reported-by: Alexei Starovoitov <ast@...nel.org>
Tested-by: Mathieu Malaterre <malat@...ian.org>
Signed-off-by: Yonghong Song <yhs@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/bpf/lpm_trie.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -470,7 +470,10 @@ static void trie_free(struct bpf_map *ma
 	struct lpm_trie_node __rcu **slot;
 	struct lpm_trie_node *node;
 
-	raw_spin_lock(&trie->lock);
+	/* Wait for outstanding programs to complete
+	 * update/lookup/delete/get_next_key and free the trie.
+	 */
+	synchronize_rcu();
 
 	/* Always start at the root and walk down to a node that has no
 	 * children. Then free that node, nullify its reference in the parent
@@ -484,7 +487,7 @@ static void trie_free(struct bpf_map *ma
 			node = rcu_dereference_protected(*slot,
 					lockdep_is_held(&trie->lock));
 			if (!node)
-				goto unlock;
+				goto out;
 
 			if (rcu_access_pointer(node->child[0])) {
 				slot = &node->child[0];
@@ -502,8 +505,8 @@ static void trie_free(struct bpf_map *ma
 		}
 	}
 
-unlock:
-	raw_spin_unlock(&trie->lock);
+out:
+	kfree(trie);
 }
 
 static int trie_get_next_key(struct bpf_map *map, void *key, void *next_key)