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authorYonghong Song <yhs@fb.com>2018-02-22 10:10:35 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-02-22 21:29:12 +0100
commit6c5f61023c5b0edb0c8a64c902fe97c6453b1852 (patch)
treeec8f2b17b7cde6332e8509c090f8f0f6ca9b9ef3
parent32fff239de37ef226d5b66329dd133f64d63b22d (diff)
downloadlinux-stericsson-6c5f61023c5b0edb0c8a64c902fe97c6453b1852.tar.gz
bpf: fix rcu lockdep warning for lpm_trie map_free callback
Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function") fixed a memory leak and removed unnecessary locks in map_free callback function. Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on, running tools/testing/selftests/bpf/test_lpm_map will have: [ 98.294321] ============================= [ 98.294807] WARNING: suspicious RCU usage [ 98.295359] 4.16.0-rc2+ #193 Not tainted [ 98.295907] ----------------------------- [ 98.296486] /home/yhs/work/bpf/kernel/bpf/lpm_trie.c:572 suspicious rcu_dereference_check() usage! [ 98.297657] [ 98.297657] other info that might help us debug this: [ 98.297657] [ 98.298663] [ 98.298663] rcu_scheduler_active = 2, debug_locks = 1 [ 98.299536] 2 locks held by kworker/2:1/54: [ 98.300152] #0: ((wq_completion)"events"){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0 [ 98.301381] #1: ((work_completion)(&map->work)){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0 Since actual trie tree removal happens only after no other accesses to the tree are possible, replacing rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock)) with rcu_dereference_protected(*slot, 1) fixed the issue. Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function") Reported-by: Eric Dumazet <edumazet@google.com> Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
-rw-r--r--kernel/bpf/lpm_trie.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index a75e02c961b5..b4b5b81e7251 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -569,8 +569,7 @@ static void trie_free(struct bpf_map *map)
slot = &trie->root;
for (;;) {
- node = rcu_dereference_protected(*slot,
- lockdep_is_held(&trie->lock));
+ node = rcu_dereference_protected(*slot, 1);
if (!node)
goto out;