bpf, sockmap: Check for any of tcp_bpf_prots when cloning a listener

A listening socket linked to a sockmap has its sk_prot overridden. It
points to one of the struct proto variants in tcp_bpf_prots. The variant
depends on the socket's family and which sockmap programs are attached.

A child socket cloned from a TCP listener initially inherits their sk_prot.
But before cloning is finished, we restore the child's proto to the
listener's original non-tcp_bpf_prots one. This happens in
tcp_create_openreq_child -> tcp_bpf_clone.

Today, in tcp_bpf_clone we detect if the child's proto should be restored
by checking only for the TCP_BPF_BASE proto variant. This is not
correct. The sk_prot of listening socket linked to a sockmap can point to
to any variant in tcp_bpf_prots.

If the listeners sk_prot happens to be not the TCP_BPF_BASE variant, then
the child socket unintentionally is left if the inherited sk_prot by
tcp_bpf_clone.

This leads to issues like infinite recursion on close [1], because the
child state is otherwise not set up for use with tcp_bpf_prot operations.

Adjust the check in tcp_bpf_clone to detect all of tcp_bpf_prots variants.

Note that it wouldn't be sufficient to check the socket state when
overriding the sk_prot in tcp_bpf_update_proto in order to always use the
TCP_BPF_BASE variant for listening sockets. Since commit
b8b8315e39ff ("bpf, sockmap: Remove unhash handler for BPF sockmap usage")
it is possible for a socket to transition to TCP_LISTEN state while already
linked to a sockmap, e.g. connect() -> insert into map ->
connect(AF_UNSPEC) -> listen().

[1]: https://lore.kernel.org/all/00000000000073b14905ef2e7401@google.com/

Fixes: e80251555f0b ("tcp_bpf: Don't let child socket inherit parent protocol ops on copy")
Reported-by: syzbot+04c21ed96d861dccc5cd@syzkaller.appspotmail.com
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20230113-sockmap-fix-v2-2-1e0ee7ac2f90@cloudflare.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/util_macros.h b/include/linux/util_macros.h
index 72299f261b25..43db6e47503c 100644
--- a/include/linux/util_macros.h
+++ b/include/linux/util_macros.h
@@ -38,4 +38,16 @@
  */
 #define find_closest_descending(x, a, as) __find_closest(x, a, as, >=)
 
+/**
+ * is_insidevar - check if the @ptr points inside the @var memory range.
+ * @ptr:	the pointer to a memory address.
+ * @var:	the variable which address and size identify the memory range.
+ *
+ * Evaluates to true if the address in @ptr lies within the memory
+ * range allocated to @var.
+ */
+#define is_insidevar(ptr, var)						\
+	((uintptr_t)(ptr) >= (uintptr_t)(var) &&			\
+	 (uintptr_t)(ptr) <  (uintptr_t)(var) + sizeof(var))
+
 #endif