| author | Alexei Starovoitov <ast@fb.com> | 2019-05-10 02:33:53 (GMT) |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-16 17:43:40 (GMT) |
| commit | aad9db666c2546b38c8c10f424a90c2f38b65493 (patch) | |
| tree | f5f2334c0c7712687d1fdaa16c925c9aa0ef504d | |
| parent | 9b04b51089ceeccde8baafec484e1815cec5b18d (diff) | |
| download | common-aad9db666c2546b38c8c10f424a90c2f38b65493.zip common-aad9db666c2546b38c8c10f424a90c2f38b65493.tar.gz common-aad9db666c2546b38c8c10f424a90c2f38b65493.tar.bz2 | |
bpf: fix struct htab_elem layout
commit 9f691549f76d488a0c74397b3e51e943865ea01f upstream.
when htab_elem is removed from the bucket list the htab_elem.hash_node.next
field should not be overridden too early otherwise we have a tiny race window
between lookup and delete.
The bug was discovered by manual code analysis and reproducible
only with explicit udelay() in lookup_elem_raw().
Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements")
Reported-by: Jonathan Perry <jonperry@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Chenbo Feng <fengc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/bpf/hashtab.c | 28 |
1 files changed, 22 insertions, 6 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index a36a532..f9d53ac 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -41,8 +41,13 @@ enum extra_elem_state { struct htab_elem { union { struct hlist_node hash_node; - struct bpf_htab *htab; - struct pcpu_freelist_node fnode; + struct { + void *padding; + union { + struct bpf_htab *htab; + struct pcpu_freelist_node fnode; + }; + }; }; union { struct rcu_head rcu; @@ -114,8 +119,10 @@ skip_percpu_elems: if (err) goto free_elems; - pcpu_freelist_populate(&htab->freelist, htab->elems, htab->elem_size, - htab->map.max_entries); + pcpu_freelist_populate(&htab->freelist, + htab->elems + offsetof(struct htab_elem, fnode), + htab->elem_size, htab->map.max_entries); + return 0; free_elems: @@ -148,6 +155,11 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) int err, i; u64 cost; + BUILD_BUG_ON(offsetof(struct htab_elem, htab) != + offsetof(struct htab_elem, hash_node.pprev)); + BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) != + offsetof(struct htab_elem, hash_node.pprev)); + if (attr->map_flags & ~BPF_F_NO_PREALLOC) /* reserved bits should not be used */ return ERR_PTR(-EINVAL); @@ -429,9 +441,13 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key, int err = 0; if (prealloc) { - l_new = (struct htab_elem *)pcpu_freelist_pop(&htab->freelist); - if (!l_new) + struct pcpu_freelist_node *l; + + l = pcpu_freelist_pop(&htab->freelist); + if (!l) err = -E2BIG; + else + l_new = container_of(l, struct htab_elem, fnode); } else { if (atomic_inc_return(&htab->count) > htab->map.max_entries) { atomic_dec(&htab->count); |