bpf: fix a memory leak in the LRU and LRU_PERCPU hash maps
The LRU and LRU_PERCPU maps allocate a new element on update before locking the
target hash table bucket. Right after that the maps try to lock the bucket.
If this fails, then maps return -EBUSY to the caller without releasing the
allocated element. This makes the element untracked: it doesn't belong to
either of free lists, and it doesn't belong to the hash table, so can't be
re-used; this eventually leads to the permanent -ENOMEM on LRU map updates,
which is unexpected. Fix this by returning the element to the local free list
if bucket locking fails.
Fixes: 20b6cc34ea
("bpf: Avoid hashtab deadlock with map_locked")
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Link: https://lore.kernel.org/r/20230522154558.2166815-1-aspsk@isovalent.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
parent
0613d8ca9a
commit
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@ -1215,7 +1215,7 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
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ret = htab_lock_bucket(htab, b, hash, &flags);
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if (ret)
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return ret;
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goto err_lock_bucket;
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l_old = lookup_elem_raw(head, hash, key, key_size);
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@ -1236,6 +1236,7 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
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err:
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htab_unlock_bucket(htab, b, hash, flags);
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err_lock_bucket:
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if (ret)
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htab_lru_push_free(htab, l_new);
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else if (l_old)
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@ -1338,7 +1339,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
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ret = htab_lock_bucket(htab, b, hash, &flags);
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if (ret)
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return ret;
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goto err_lock_bucket;
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l_old = lookup_elem_raw(head, hash, key, key_size);
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@ -1361,6 +1362,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
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ret = 0;
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err:
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htab_unlock_bucket(htab, b, hash, flags);
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err_lock_bucket:
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if (l_new)
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bpf_lru_push_free(&htab->lru, &l_new->lru_node);
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return ret;
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