[PATCH net 2/2] vsock/bpf: return early if transport is not assigned

[Stefano Garzarella]

Some of the core functions can only be called if the transport
has been assigned.

As Michal reported, a socket might have the transport at NULL,
for example after a failed connect(), causing the following trace:

    BUG: kernel NULL pointer dereference, address: 00000000000000a0
    #PF: supervisor read access in kernel mode
    #PF: error_code(0x0000) - not-present page
    PGD 12faf8067 P4D 12faf8067 PUD 113670067 PMD 0
    Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
    CPU: 15 UID: 0 PID: 1198 Comm: a.out Not tainted 6.13.0-rc2+
    RIP: 0010:vsock_connectible_has_data+0x1f/0x40
    Call Trace:
     vsock_bpf_recvmsg+0xca/0x5e0
     sock_recvmsg+0xb9/0xc0
     __sys_recvfrom+0xb3/0x130
     __x64_sys_recvfrom+0x20/0x30
     do_syscall_64+0x93/0x180
     entry_SYSCALL_64_after_hwframe+0x76/0x7e

So we need to check the `vsk->transport` in vsock_bpf_recvmsg(),
especially for connected sockets (stream/seqpacket) as we already
do in __vsock_connectible_recvmsg().

Fixes: 634f1a7110b4 ("vsock: support sockmap")
Reported-by: Michal Luczaj <m...@rbox.co>
Closes: 
https://lore.kernel.org/netdev/5ca20d4c-1017-49c2-9516-f6f75fd33...@rbox.co/
Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
---
 net/vmw_vsock/vsock_bpf.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
index 4aa6e74ec295..f201d9eca1df 100644
--- a/net/vmw_vsock/vsock_bpf.c
+++ b/net/vmw_vsock/vsock_bpf.c
@@ -77,6 +77,7 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr 
*msg,
                             size_t len, int flags, int *addr_len)
 {
        struct sk_psock *psock;
+       struct vsock_sock *vsk;
        int copied;
 
        psock = sk_psock_get(sk);
@@ -84,6 +85,13 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr 
*msg,
                return __vsock_recvmsg(sk, msg, len, flags);
 
        lock_sock(sk);
+       vsk = vsock_sk(sk);
+
+       if (!vsk->transport) {
+               copied = -ENODEV;
+               goto out;
+       }
+
        if (vsock_has_data(sk, psock) && sk_psock_queue_empty(psock)) {
                release_sock(sk);
                sk_psock_put(sk, psock);
@@ -108,6 +116,7 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr 
*msg,
                copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
        }
 
+out:
        release_sock(sk);
        sk_psock_put(sk, psock);
 
-- 
2.47.1