From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Date: Mon, 18 Mar 2013 13:55:03 +0300
> This is a user pointer. Changing the memcpy() to copy_to_user()
> fixes a hang on my system.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> I'm not very familiar with this code, so please review this
> carefully.
It really should be a kernel pointer, not a user pointer.
For example, look at how recvfrom() cooks up a recvmsg method
call:
struct sockaddr_storage address;
...
msg.msg_name = (struct sockaddr *)&address;
msg.msg_namelen = sizeof(address);
...
err = sock_recvmsg(sock, &msg, size, flags);
recvmsg() proper works similarly, copying the user msghdr into a
kernel space copy via verify_iovec() or verify_compat_iovec() (and
I can understand how it's not obvious that this is the function
that performs this operation).
> /* copy the peer address and timestamp */
> if (!continue_call) {
> - if (msg->msg_name && msg->msg_namelen > 0)
> - memcpy(msg->msg_name,
> - &call->conn->trans->peer->srx,
> - sizeof(call->conn->trans->peer->srx));
I bet the size is too large for a sockaddr_storage, and therefore we
spam the kernel stack. So I can only guess that changing this to a
copy_to_user() fixes the hang because it simply faults on the kernel
destination address.
->srx should be a "struct sockaddr_rxrpc" but that doesn't appear to
exceed the 128-byte size of sockaddr_storage.
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