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author | Toke Høiland-Jørgensen <toke@redhat.com> | 2021-06-24 18:05:54 +0200 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2021-06-24 19:41:15 +0200 |
commit | 694cea395fded425008e93cd90cfdf7a451674af (patch) | |
tree | be068946c3b7fd801c7d8854947c4d090de9896b | |
parent | e74c74f9e51deb725e72d129084ba8252d47222d (diff) | |
download | linux-stable-694cea395fded425008e93cd90cfdf7a451674af.tar.gz linux-stable-694cea395fded425008e93cd90cfdf7a451674af.tar.bz2 linux-stable-694cea395fded425008e93cd90cfdf7a451674af.zip |
bpf: Allow RCU-protected lookups to happen from bh context
XDP programs are called from a NAPI poll context, which means the RCU
reference liveness is ensured by local_bh_disable(). Add
rcu_read_lock_bh_held() as a condition to the RCU checks for map lookups so
lockdep understands that the dereferences are safe from inside *either* an
rcu_read_lock() section *or* a local_bh_disable() section. While both
bh_disabled and rcu_read_lock() provide RCU protection, they are
semantically distinct, so we need both conditions to prevent lockdep
complaints.
This change is done in preparation for removing the redundant
rcu_read_lock()s from drivers.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210624160609.292325-5-toke@redhat.com
-rw-r--r-- | kernel/bpf/hashtab.c | 21 | ||||
-rw-r--r-- | kernel/bpf/helpers.c | 6 | ||||
-rw-r--r-- | kernel/bpf/lpm_trie.c | 6 |
3 files changed, 21 insertions, 12 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 6f6681b07364..72c58cc516a3 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -596,7 +596,8 @@ static void *__htab_map_lookup_elem(struct bpf_map *map, void *key) struct htab_elem *l; u32 hash, key_size; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; @@ -989,7 +990,8 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value, /* unknown flags */ return -EINVAL; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; @@ -1082,7 +1084,8 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value, /* unknown flags */ return -EINVAL; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; @@ -1148,7 +1151,8 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key, /* unknown flags */ return -EINVAL; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; @@ -1202,7 +1206,8 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key, /* unknown flags */ return -EINVAL; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; @@ -1276,7 +1281,8 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key) u32 hash, key_size; int ret; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; @@ -1311,7 +1317,8 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key) u32 hash, key_size; int ret; - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && + !rcu_read_lock_bh_held()); key_size = map->key_size; diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index a2f1f15ce432..62cf00383910 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -29,7 +29,7 @@ */ BPF_CALL_2(bpf_map_lookup_elem, struct bpf_map *, map, void *, key) { - WARN_ON_ONCE(!rcu_read_lock_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); return (unsigned long) map->ops->map_lookup_elem(map, key); } @@ -45,7 +45,7 @@ const struct bpf_func_proto bpf_map_lookup_elem_proto = { BPF_CALL_4(bpf_map_update_elem, struct bpf_map *, map, void *, key, void *, value, u64, flags) { - WARN_ON_ONCE(!rcu_read_lock_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); return map->ops->map_update_elem(map, key, value, flags); } @@ -62,7 +62,7 @@ const struct bpf_func_proto bpf_map_update_elem_proto = { BPF_CALL_2(bpf_map_delete_elem, struct bpf_map *, map, void *, key) { - WARN_ON_ONCE(!rcu_read_lock_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); return map->ops->map_delete_elem(map, key); } diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 1b7b8a6f34ee..423549d2c52e 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -232,7 +232,8 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) /* Start walking the trie from the root node ... */ - for (node = rcu_dereference(trie->root); node;) { + for (node = rcu_dereference_check(trie->root, rcu_read_lock_bh_held()); + node;) { unsigned int next_bit; size_t matchlen; @@ -264,7 +265,8 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) * traverse down. */ next_bit = extract_bit(key->data, node->prefixlen); - node = rcu_dereference(node->child[next_bit]); + node = rcu_dereference_check(node->child[next_bit], + rcu_read_lock_bh_held()); } if (!found) |