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

[Hyunwoo Kim <imv4bel@gmail.com>]

On Wed, Nov 04, 2026 at 08:59:50AM +0100, Paolo Abeni wrote:
> On 11/4/26 02:24, Hyunwoo Kim wrote:
> > 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?
> 
> Ideally the cover letter should include a very quick/short overview of the
> changes, and a per patch changelog should include a more detailed list
> (no entry added when the patch is unmodified).

Understood. I'll do that from now on.


Best regards,
Hyunwoo Kim