Re: [PATCH net-next] kcm: do not attach sockets if sk_user_data is already used

On 16 January 2018 at 19:00, David Miller [off-list ref] wrote:

From: Tom Herbert <redacted>
Date: Tue, 16 Jan 2018 09:36:41 -0800

quoted

sk_user_data is set with the sk_callback lock held in code below.
Should be able to take the lock earlier can do this check under the
lock.

csock, and this csk, is obtained from an arbitrary one of the
process's FDs.  It can be any socket type or family, and that socket's
family might set sk_user_data without the callback lock.

The only socket type check is making sure it is not another PF_KCM
socket.  So that doesn't help with this problem.

Is it the intention to update all socket code over time to write
sk_user_data within the sk_callback lock? If so, I'm happy to address
that in the l2tp code (and update the kcm patch to check sk_user_data
within the sk_callback lock). Or is the preferred solution to restrict
KCM to specific socket families, as suggested by Guillaume earlier in
the thread?