Re: [PATCH net v5 2/2] net: restore refcount ordering for lockless socket access

[Hyunwoo Kim <imv4bel@gmail.com>]

On Tue, Nov 03, 2026 at 03:49:40PM +0100, Eric Dumazet wrote:
> Le jeu. 29 oct. 2026 à 22:42, Hyunwoo Kim <imv4bel@gmail.com> a écrit :
> >
> > Before commit fb041bb7c0a9 ("locking/refcount: Consolidate implementations
> > of refcount_t"), default builds implemented refcount_inc_not_zero() using
> > atomic_add_unless(), which provided full memory ordering on success. The
> > commit removed that ordering on weakly ordered architectures, allowing
> > accesses after a successful reference acquisition to be reordered before
> > it.
> >
> > Use refcount_inc_not_zero_acquire() in the IPv4 and IPv6 established
> > lookups and in inet_twsk_purge(), where the socket is validated again
> > after taking a reference.
> >
> > bpf_sk_assign() can receive a socket pointer obtained through BTF
> > without a reference. Use acquire ordering when it takes its own reference
> > for a refcounted socket.
> >
> > Use refcount_set_release() when setting refcounts in the SYN cookie,
> > TCP Fast Open, request migration, and TIME_WAIT paths. Keep the existing
> > TIME_WAIT smp_wmb(), which separately orders the refcount store before
> > ehash publication.
> >
> > Fixes: fb041bb7c0a9 ("locking/refcount: Consolidate implementations of refcount_t")
> > Fixes: 27e5203bd9c5 ("bpf: Change bpf_sk_assign to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> > ---
> 
> Lack of links to prior versions is rather annoying.

Is the cover letter alone insufficient?

Should the changelog be in each patch?