[Linux-kernel-mentees] [PATCH] bpf: devmap: Pass lockdep expression to RCU lists

Amol Grover frextrite at gmail.com
Thu Jan 23 12:04:38 UTC 2020

head is traversed using hlist_for_each_entry_rcu outside an
RCU read-side critical section but under the protection
of dtab->index_lock.

Hence, add corresponding lockdep expression to silence false-positive
lockdep warnings, and harden RCU lists.

Signed-off-by: Amol Grover <frextrite at gmail.com>
 kernel/bpf/devmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 3d3d61b5985b..b4b6b77f309c 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -293,7 +293,8 @@ struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
 	struct hlist_head *head = dev_map_index_hash(dtab, key);
 	struct bpf_dtab_netdev *dev;
-	hlist_for_each_entry_rcu(dev, head, index_hlist)
+	hlist_for_each_entry_rcu(dev, head, index_hlist,
+				 lockdep_is_held(&dtab->index_lock))
 		if (dev->idx == key)
 			return dev;

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