UDP sockets get SOCK_RCU_FREE set when (auto-)bound. This means
sk_is_refcounted(unbound) = true, while sk_is_refcounted(bound) = false.
Because sockmap accepts unbound UDP sockets, a BPF program can increment a
socket's refcount via lookup. If the socket is subsequently bound, the
transition from unbound to bound causes bpf_sk_release() to skip the
decrement of the refcount, causing a memory leak.
unreferenced object 0xffff88810bc2eb40 (size 1984):
comm "test_progs", pid 2451, jiffies 4295320596
hex dump (first 32 bytes):
7f 00 00 01 7f 00 00 01 d2 04 1b b7 04 d2 00 00 ................
02 00 01 40 00 00 00 00 00 00 00 00 00 00 00 00 ...@............
backtrace (crc bdee079d):
kmem_cache_alloc_noprof+0x557/0x660
sk_prot_alloc+0x69/0x240
sk_alloc+0x30/0x460
inet_create+0x2ce/0xf80
__sock_create+0x25b/0x5c0
__sys_socket+0x119/0x1d0
__x64_sys_socket+0x72/0xd0
do_syscall_64+0xa1/0x5f0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Instead of special-casing for refcounted sockets, reject unhashed UDP
sockets during sockmap updates, as there is no benefit to supporting those.
This effectively reverts the commit under Fixes, with two exceptions:
1. sock_map_sk_state_allowed() maintains a fall-through `return true`.
2. In the spirit of commit b8b8315e39ff ("bpf, sockmap: Remove unhash
handler for BPF sockmap usage"), the proto::unhash BPF handler is not
reintroduced.
Historical note: this issue is related to commit 67312adc96b5 ("bpf: reject
unhashed sockets in bpf_sk_assign").
Fixes: 0c48eefae712 ("sock_map: Lift socket state restriction for datagram
sockets")
Suggested-by: Kuniyuki Iwashima <[email protected]>
Signed-off-by: Michal Luczaj <[email protected]>
---
net/core/sock_map.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index c60ba6d292f9..9efbd8ca7db8 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -542,6 +542,8 @@ static bool sock_map_sk_state_allowed(const struct sock *sk)
{
if (sk_is_tcp(sk))
return (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_LISTEN);
+ if (sk_is_udp(sk))
+ return sk_hashed(sk);
if (sk_is_stream_unix(sk))
return (1 << READ_ONCE(sk->sk_state)) & TCPF_ESTABLISHED;
if (sk_is_vsock(sk) &&
--
2.54.0
