diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2024-03-29 10:14:39 -0700 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2024-03-29 11:10:41 -0700 |
| commit | 59f2f841179aa6a0899cb9cf53659149a35749b7 (patch) | |
| tree | 6062529deb60350ea15098e82d721feda3661b6a | |
| parent | 201874fc064ef14c26ea87a890b3f58296750d2d (diff) | |
bpf: Avoid kfree_rcu() under lock in bpf_lpm_trie.
syzbot reported the following lock sequence:
cpu 2:
grabs timer_base lock
spins on bpf_lpm lock
cpu 1:
grab rcu krcp lock
spins on timer_base lock
cpu 0:
grab bpf_lpm lock
spins on rcu krcp lock
bpf_lpm lock can be the same.
timer_base lock can also be the same due to timer migration.
but rcu krcp lock is always per-cpu, so it cannot be the same lock.
Hence it's a false positive.
To avoid lockdep complaining move kfree_rcu() after spin_unlock.
Reported-by: syzbot+1fa663a2100308ab6eab@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240329171439.37813-1-alexei.starovoitov@gmail.com
| -rw-r--r-- | kernel/bpf/lpm_trie.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 939620b91c0ea..0218a5132ab56 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -316,6 +316,7 @@ static long trie_update_elem(struct bpf_map *map, { struct lpm_trie *trie = container_of(map, struct lpm_trie, map); struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL; + struct lpm_trie_node *free_node = NULL; struct lpm_trie_node __rcu **slot; struct bpf_lpm_trie_key_u8 *key = _key; unsigned long irq_flags; @@ -390,7 +391,7 @@ static long trie_update_elem(struct bpf_map *map, trie->n_entries--; rcu_assign_pointer(*slot, new_node); - kfree_rcu(node, rcu); + free_node = node; goto out; } @@ -437,6 +438,7 @@ out: } spin_unlock_irqrestore(&trie->lock, irq_flags); + kfree_rcu(free_node, rcu); return ret; } @@ -445,6 +447,7 @@ out: static long trie_delete_elem(struct bpf_map *map, void *_key) { struct lpm_trie *trie = container_of(map, struct lpm_trie, map); + struct lpm_trie_node *free_node = NULL, *free_parent = NULL; struct bpf_lpm_trie_key_u8 *key = _key; struct lpm_trie_node __rcu **trim, **trim2; struct lpm_trie_node *node, *parent; @@ -514,8 +517,8 @@ static long trie_delete_elem(struct bpf_map *map, void *_key) else rcu_assign_pointer( *trim2, rcu_access_pointer(parent->child[0])); - kfree_rcu(parent, rcu); - kfree_rcu(node, rcu); + free_parent = parent; + free_node = node; goto out; } @@ -529,10 +532,12 @@ static long trie_delete_elem(struct bpf_map *map, void *_key) rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1])); else RCU_INIT_POINTER(*trim, NULL); - kfree_rcu(node, rcu); + free_node = node; out: spin_unlock_irqrestore(&trie->lock, irq_flags); + kfree_rcu(free_parent, rcu); + kfree_rcu(free_node, rcu); return ret; } |