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Eric Dumazet
e974a10a52
[ Upstream commitf613e8b4af] Yin Fengwei reported an RCU stall in ptype_seq_show() and provided a patch. Real issue is that ptype_seq_next() and ptype_seq_show() violate RCU rules. ptype_seq_show() runs under rcu_read_lock(), and reads pt->dev to get device name without any barrier. At the same time, concurrent writers can remove a packet_type structure (which is correctly freed after an RCU grace period) and clear pt->dev without an RCU grace period. Define ptype_iter_state to carry a dev pointer along seq_net_private: struct ptype_iter_state { struct seq_net_private p; struct net_device *dev; // added in this patch }; We need to record the device pointer in ptype_get_idx() and ptype_seq_next() so that ptype_seq_show() is safe against concurrent pt->dev changes. We also need to add full RCU protection in ptype_seq_next(). (Missing READ_ONCE() when reading list.next values) Many thanks to Dong Chenchen for providing a repro. Fixes:1da177e4c3("Linux-2.6.12-rc2") Fixes:1d10f8a1f4("net-procfs: show net devices bound packet types") Fixes:c353e8983e("net: introduce per netns packet chains") Reported-by: Yin Fengwei <fengwei_yin@linux.alibaba.com> Reported-by: Dong Chenchen <dongchenchen2@huawei.com> Closes: https://lore.kernel.org/netdev/CANn89iKRRKPnWjJmb-_3a=sq+9h6DvTQM4DBZHT5ZRGPMzQaiA@mail.gmail.com/T/#m7b80b9fc9b9267f90e0b7aad557595f686f9c50d Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Tested-by: Yin Fengwei <fengwei_yin@linux.alibaba.com> Link: https://patch.msgid.link/20260202205217.2881198-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> [ Some adjustments have been made. ] Signed-off-by: XiaoHua Wang <561399680@139.com> Signed-off-by: Sasha Levin <sashal@kernel.org>