Re: [PATCH] net: Fix suspicious RCU usage in bpf_sk_reuseport_detach()

[Jakub Kicinski]

On Tue, 16 Aug 2022 17:43:19 -0700 Martin KaFai Lau wrote:
> > I like your version because it documents what the lock protecting this
> > field is.
> > 
> > In fact should we also add && sock_owned_by_user(). Martin, WDYT? Would
> > that work for reuseport? Jakub S is fixing l2tp to hold the socket lock
> > while setting this field, yet most places take the callback lock...  
>
> It needs to take a closer look at where the lock_sock() has already
> been acquired and also need to consider the lock ordering with reuseport_lock.
> It probably should work but may need a separate patch to discuss those
> considerations ?

Right, the users of the field with a bit allocated protect the writes
with the callback lock, so we can hard code the check against the
callback lock for now and revisit later if needed.