| Message ID | 20200206111652.694507-3-jakub@cloudflare.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | Fix locking order and synchronization on sockmap/sockhash tear-down | expand |
Jakub Sitnicki wrote: > We need to have a synchronize_rcu before free'ing the sockhash because any > outstanding psock references will have a pointer to the map and when they > use it, this could trigger a use after free. > > This is a sister fix for sockhash, following commit 2bb90e5cc90e ("bpf: > sockmap, synchronize_rcu before free'ing map") which addressed sockmap, > which comes from a manual audit. > > Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface") > Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> > --- > net/core/sock_map.c | 4 ++++ > 1 file changed, 4 insertions(+) Nice catch thanks. As far as I know I've never seen this happen but lets get this fixed. Acked-by: John Fastabend <john.fastabend@gmail.com> > > diff --git a/net/core/sock_map.c b/net/core/sock_map.c > index fd8b426dbdf3..f36e13e577a3 100644 > --- a/net/core/sock_map.c > +++ b/net/core/sock_map.c > @@ -250,6 +250,7 @@ static void sock_map_free(struct bpf_map *map) > } > raw_spin_unlock_bh(&stab->lock); > > + /* wait for psock readers accessing its map link */ > synchronize_rcu(); > > bpf_map_area_free(stab->sks); > @@ -873,6 +874,9 @@ static void sock_hash_free(struct bpf_map *map) > raw_spin_unlock_bh(&bucket->lock); > } > > + /* wait for psock readers accessing its map link */ > + synchronize_rcu(); > + > bpf_map_area_free(htab->buckets); > kfree(htab); > } > -- > 2.24.1 >
diff --git a/net/core/sock_map.c b/net/core/sock_map.c index fd8b426dbdf3..f36e13e577a3 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -250,6 +250,7 @@ static void sock_map_free(struct bpf_map *map) } raw_spin_unlock_bh(&stab->lock); + /* wait for psock readers accessing its map link */ synchronize_rcu(); bpf_map_area_free(stab->sks); @@ -873,6 +874,9 @@ static void sock_hash_free(struct bpf_map *map) raw_spin_unlock_bh(&bucket->lock); } + /* wait for psock readers accessing its map link */ + synchronize_rcu(); + bpf_map_area_free(htab->buckets); kfree(htab); }
We need to have a synchronize_rcu before free'ing the sockhash because any outstanding psock references will have a pointer to the map and when they use it, this could trigger a use after free. This is a sister fix for sockhash, following commit 2bb90e5cc90e ("bpf: sockmap, synchronize_rcu before free'ing map") which addressed sockmap, which comes from a manual audit. Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface") Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> --- net/core/sock_map.c | 4 ++++ 1 file changed, 4 insertions(+)