diff options
author | John Fastabend <john.fastabend@gmail.com> | 2023-12-22 02:23:23 +0300 |
---|---|---|
committer | Martin KaFai Lau <martin.lau@kernel.org> | 2024-01-04 03:50:06 +0300 |
commit | 16b2f264983dc264c1560cc0170e760dec1bf54f (patch) | |
tree | 6193fe6512ba7c9095c01278510cefc390cd2e7f | |
parent | b4560055c8f11c5e2cfffb4de928b3cfd4eae3b4 (diff) | |
download | linux-16b2f264983dc264c1560cc0170e760dec1bf54f.tar.xz |
bpf: sockmap, fix proto update hook to avoid dup calls
When sockets are added to a sockmap or sockhash we allocate and init a
psock. Then update the proto ops with sock_map_init_proto the flow is
sock_hash_update_common
sock_map_link
psock = sock_map_psock_get_checked() <-returns existing psock
sock_map_init_proto(sk, psock) <- updates sk_proto
If the socket is already in a map this results in the sock_map_init_proto
being called multiple times on the same socket. We do this because when
a socket is added to multiple maps this might result in a new set of BPF
programs being attached to the socket requiring an updated ops struct.
This creates a rule where it must be safe to call psock_update_sk_prot
multiple times. When we added a fix for UAF through unix sockets in patch
4dd9a38a753fc we broke this rule by adding a sock_hold in that path
to ensure the sock is not released. The result is if a af_unix stream sock
is placed in multiple maps it results in a memory leak because we call
sock_hold multiple times with only a single sock_put on it.
Fixes: 8866730aed51 ("bpf, sockmap: af_unix stream sockets need to hold ref for pair sock")
Reported-by: Xingwei Lee <xrivendell7@gmail.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20231221232327.43678-2-john.fastabend@gmail.com
-rw-r--r-- | net/unix/unix_bpf.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c index 7ea7c3a0d0d0..bd84785bf8d6 100644 --- a/net/unix/unix_bpf.c +++ b/net/unix/unix_bpf.c @@ -161,15 +161,30 @@ int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool r { struct sock *sk_pair; + /* Restore does not decrement the sk_pair reference yet because we must + * keep the a reference to the socket until after an RCU grace period + * and any pending sends have completed. + */ if (restore) { sk->sk_write_space = psock->saved_write_space; sock_replace_proto(sk, psock->sk_proto); return 0; } - sk_pair = unix_peer(sk); - sock_hold(sk_pair); - psock->sk_pair = sk_pair; + /* psock_update_sk_prot can be called multiple times if psock is + * added to multiple maps and/or slots in the same map. There is + * also an edge case where replacing a psock with itself can trigger + * an extra psock_update_sk_prot during the insert process. So it + * must be safe to do multiple calls. Here we need to ensure we don't + * increment the refcnt through sock_hold many times. There will only + * be a single matching destroy operation. + */ + if (!psock->sk_pair) { + sk_pair = unix_peer(sk); + sock_hold(sk_pair); + psock->sk_pair = sk_pair; + } + unix_stream_bpf_check_needs_rebuild(psock->sk_proto); sock_replace_proto(sk, &unix_stream_bpf_prot); return 0; |