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authorAnton Protopopov <aspsk@isovalent.com>2023-05-22 18:45:58 +0300
committerMartin KaFai Lau <martin.lau@kernel.org>2023-05-22 20:26:39 +0300
commitb34ffb0c6d23583830f9327864b9c1f486003305 (patch)
treec628f2bc7f4f6c1a0399fdb94ec897357b41444a
parent0613d8ca9ab382caabe9ed2dceb429e9781e443f (diff)
downloadlinux-b34ffb0c6d23583830f9327864b9c1f486003305.tar.xz
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: 20b6cc34ea74 ("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>
-rw-r--r--kernel/bpf/hashtab.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 00c253b84bf5..9901efee4339 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1215,7 +1215,7 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
ret = htab_lock_bucket(htab, b, hash, &flags);
if (ret)
- return ret;
+ goto err_lock_bucket;
l_old = lookup_elem_raw(head, hash, key, key_size);
@@ -1236,6 +1236,7 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
err:
htab_unlock_bucket(htab, b, hash, flags);
+err_lock_bucket:
if (ret)
htab_lru_push_free(htab, l_new);
else if (l_old)
@@ -1338,7 +1339,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
ret = htab_lock_bucket(htab, b, hash, &flags);
if (ret)
- return ret;
+ goto err_lock_bucket;
l_old = lookup_elem_raw(head, hash, key, key_size);
@@ -1361,6 +1362,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
ret = 0;
err:
htab_unlock_bucket(htab, b, hash, flags);
+err_lock_bucket:
if (l_new)
bpf_lru_push_free(&htab->lru, &l_new->lru_node);
return ret;