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Sun, 09 Aug 2026 19:23:47 -0700 (PDT) Received: from fedora ([203.175.12.242]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84f5a58bd4bsm3074067b3a.56.2026.08.09.19.23.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 09 Aug 2026 19:23:46 -0700 (PDT) Date: Mon, 10 Aug 2026 10:23:35 +0800 From: Hangbin Liu To: Xin Xie Cc: netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, andrew+netdev@lunn.ch, shuah@kernel.org, kees@kernel.org, petr.wozniak@gmail.com, qingfang.deng@linux.dev, fmaurer@redhat.com, luka.gejak@linux.dev, bigeasy@linutronix.de, xiaoliang.yang_1@nxp.com, skhawaja@google.com, stable@vger.kernel.org, sdf.kernel@gmail.com, syzbot+fbf74291c3b7e753b481@syzkaller.appspotmail.com Subject: Re: [PATCH 2/4] net: hsr: shrink seqnr_lock to sequence counter updates Message-ID: References: <20260809121455.1745-1-xiexinet@gmail.com> <20260809121455.1745-3-xiexinet@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260809121455.1745-3-xiexinet@gmail.com> On Sun, Aug 09, 2026 at 02:14:52PM +0200, Xin Xie wrote: > Commit 06afd2c31d33 ("hsr: Synchronize sending frames to have always > incremented outgoing seq nr.") and commit 430d67bdcb04 ("net: hsr: Use > the seqnr lock for frames received via interlink port.") hold > seqnr_lock across the whole forwarding path. Transmitting while > holding the lock can create lock-dependency issues when HSR devices > are stacked with other net devices, up to a real deadlock (see > Reported-by/Closes). > > Since commit aae9d6b616b5 ("hsr: Implement more robust duplicate > discard for HSR"), duplicate discard is order-independent (sparse > bitmaps), so only the sequence counter updates need serialization. > Limit seqnr_lock to the counter updates in handle_std_frame(); the > master TX path (hsr_dev_xmit()) and the interlink RX path > (hsr_handle_frame()) drop their outer lock, and the supervision frame > builders release it right after their counter update. > > Concurrent forwarding may emit frames out of allocation order, which > sparse-bitmap discard tolerates. The master/interlink tx statistics are > no longer serialized; consistent per-cpu/per-queue statistics for all > HSR paths are handled in a separate series. > > Fixes: 06afd2c31d33 ("hsr: Synchronize sending frames to have always incremented outgoing seq nr.") > Fixes: 430d67bdcb04 ("net: hsr: Use the seqnr lock for frames received via interlink port.") > Reported-by: syzbot+fbf74291c3b7e753b481@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=fbf74291c3b7e753b481 > Cc: # aae9d6b616b5: hsr: Implement more robust duplicate discard for HSR > Signed-off-by: Xin Xie > --- > net/hsr/hsr_device.c | 15 ++++----------- > net/hsr/hsr_forward.c | 3 ++- > net/hsr/hsr_slave.c | 11 +---------- > 3 files changed, 7 insertions(+), 22 deletions(-) > > diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c > index 5555b71ab19b..3fd1762d8916 100644 > --- a/net/hsr/hsr_device.c > +++ b/net/hsr/hsr_device.c > @@ -232,9 +232,7 @@ static netdev_tx_t hsr_dev_xmit(struct sk_buff *skb, struct net_device *dev) > skb->dev = master->dev; > skb_reset_mac_header(skb); > skb_reset_mac_len(skb); > - spin_lock_bh(&hsr->seqnr_lock); > hsr_forward_skb(skb, master); > - spin_unlock_bh(&hsr->seqnr_lock); > } else { > dev_core_stats_tx_dropped_inc(dev); > dev_kfree_skb_any(skb); > @@ -335,6 +333,7 @@ static void send_hsr_supervision_frame(struct hsr_port *port, > hsr_stag->sequence_nr = htons(hsr->sequence_nr); > hsr->sequence_nr++; > } > + spin_unlock_bh(&hsr->seqnr_lock); > > hsr_stag->tlv.HSR_TLV_type = type; > /* HSRv0 has 6 unused bytes after the MAC */ > @@ -356,14 +355,10 @@ static void send_hsr_supervision_frame(struct hsr_port *port, > ether_addr_copy(hsr_sp->macaddress_A, hsr->macaddress_redbox); > } > > - if (skb_put_padto(skb, ETH_ZLEN)) { > - spin_unlock_bh(&hsr->seqnr_lock); > + if (skb_put_padto(skb, ETH_ZLEN)) > return; > - } > > hsr_forward_skb(skb, port); > - spin_unlock_bh(&hsr->seqnr_lock); > - return; > } > > static void send_prp_supervision_frame(struct hsr_port *master, > @@ -390,6 +385,7 @@ static void send_prp_supervision_frame(struct hsr_port *master, > spin_lock_bh(&hsr->seqnr_lock); > hsr_stag->sequence_nr = htons(hsr->sup_sequence_nr); > hsr->sup_sequence_nr++; > + spin_unlock_bh(&hsr->seqnr_lock); > hsr_stag->tlv.HSR_TLV_type = PRP_TLV_LIFE_CHECK_DD; > hsr_stag->tlv.HSR_TLV_length = sizeof(struct hsr_sup_payload); > > @@ -397,13 +393,10 @@ static void send_prp_supervision_frame(struct hsr_port *master, > hsr_sp = skb_put(skb, sizeof(struct hsr_sup_payload)); > ether_addr_copy(hsr_sp->macaddress_A, master->dev->dev_addr); > > - if (skb_put_padto(skb, ETH_ZLEN)) { > - spin_unlock_bh(&hsr->seqnr_lock); > + if (skb_put_padto(skb, ETH_ZLEN)) > return; > - } > > hsr_forward_skb(skb, master); > - spin_unlock_bh(&hsr->seqnr_lock); > } > > /* Announce (supervision frame) timer function > diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c > index 0774981a65c1..8e4158a9b57c 100644 > --- a/net/hsr/hsr_forward.c > +++ b/net/hsr/hsr_forward.c > @@ -621,9 +621,10 @@ static void handle_std_frame(struct sk_buff *skb, > if (port->type == HSR_PT_MASTER || > port->type == HSR_PT_INTERLINK) { > /* Sequence nr for the master/interlink node */ > - lockdep_assert_held(&hsr->seqnr_lock); > + spin_lock_bh(&hsr->seqnr_lock); > frame->sequence_nr = hsr->sequence_nr; > hsr->sequence_nr++; > + spin_unlock_bh(&hsr->seqnr_lock); > } > } > > diff --git a/net/hsr/hsr_slave.c b/net/hsr/hsr_slave.c > index bb2182a169a3..8b96eafe15b3 100644 > --- a/net/hsr/hsr_slave.c > +++ b/net/hsr/hsr_slave.c > @@ -73,16 +73,7 @@ static rx_handler_result_t hsr_handle_frame(struct sk_buff **pskb) > } > skb_reset_mac_len(skb); > > - /* Only the frames received over the interlink port will assign a > - * sequence number and require synchronisation vs other sender. > - */ > - if (port->type == HSR_PT_INTERLINK) { > - spin_lock_bh(&hsr->seqnr_lock); > - hsr_forward_skb(skb, port); > - spin_unlock_bh(&hsr->seqnr_lock); > - } else { > - hsr_forward_skb(skb, port); > - } > + hsr_forward_skb(skb, port); > > finish_consume: > return RX_HANDLER_CONSUMED; > -- > 2.43.0 > Thanks for the fix. Reviewed-by: Hangbin Liu