Re: [PATCH] compat bug in sys_recvmsg, MSG_CMSG_COMPAT check missing

["David S. Miller" <davem@xxxxxxxxxx>]

On Sat, 5 Jun 2004 22:43:34 +0200
Olaf Hering <olh@xxxxxxx> wrote:

> packet_recvmsg() gets the flags from the compat_sys_socketcall(), but it
> does not check for the active MSG_CMSG_COMPAT bit. As a result, it
> returns -EINVAL and makes the user rather unhappy

Not just packet_recvmsg() (frankly, I'm stumped how tcpdump is working
on my sparc64 boxes due to this bug!), every other sendmsg/recvmsg
implementation has a test like this verifying the msg_flags for bogons.

Let's ask a better question, why do we need to pass this thing down
into the implementations anyways?

I can't see a reason, can anyone else?  If there is no reason, the
right fix is simply to mask it out at the top level, for both
sendmsg and recvmsg.