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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id k6sm873368pju.44.2020.05.01.20.32.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 May 2020 20:32:19 -0700 (PDT) Subject: Re: [PATCH] net: fix memory leaks in flush_backlog() with RPS To: Qian Cai , davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200502031516.2825-1-cai@lca.pw> From: Eric Dumazet Message-ID: <8a012879-825f-596d-9866-0dd3a095dfbb@gmail.com> Date: Fri, 1 May 2020 20:32:17 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200502031516.2825-1-cai@lca.pw> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/1/20 8:15 PM, Qian Cai wrote: > netif_receive_skb_list_internal() could call enqueue_to_backlog() to put > some skb to softnet_data.input_pkt_queue and then in > ip_route_input_slow(), it allocates a dst_entry to be used in > skb_dst_set(). Later, > > cleanup_net > default_device_exit_batch > unregister_netdevice_many > rollback_registered_many > flush_all_backlogs > > will call flush_backlog() for all CPUs which would call kfree_skb() for > each skb on the input_pkt_queue without calling skb_dst_drop() first. > > unreferenced object 0xffff97008e4c4040 (size 176): > comm "softirq", pid 0, jiffies 4295173845 (age 32012.550s) > hex dump (first 32 bytes): > 00 d0 a5 74 04 97 ff ff 40 72 1a 96 ff ff ff ff ...t....@r...... > c1 a3 c5 95 ff ff ff ff 00 00 00 00 00 00 00 00 ................ > backtrace: > [<0000000030483fae>] kmem_cache_alloc+0x184/0x430 > [<000000007ae17545>] dst_alloc+0x8e/0x128 > [<000000001efe9a1f>] rt_dst_alloc+0x6f/0x1e0 > rt_dst_alloc at net/ipv4/route.c:1628 > [<00000000e67d4dac>] ip_route_input_rcu+0xdfe/0x1640 > ip_route_input_slow at net/ipv4/route.c:2218 > (inlined by) ip_route_input_rcu at net/ipv4/route.c:2348 > [<000000009f30cbc0>] ip_route_input_noref+0xab/0x1a0 > [<000000004f53bd04>] arp_process+0x83a/0xf50 > arp_process at net/ipv4/arp.c:813 (discriminator 1) > [<0000000061fd547d>] arp_rcv+0x276/0x330 > [<0000000007dbfa7a>] __netif_receive_skb_list_core+0x4d2/0x500 > [<0000000062d5f6d2>] netif_receive_skb_list_internal+0x4cb/0x7d0 > [<000000002baa2b74>] gro_normal_list+0x55/0xc0 > [<0000000093d04885>] napi_complete_done+0xea/0x350 > [<00000000467dd088>] tg3_poll_msix+0x174/0x310 [tg3] > [<00000000498af7d9>] net_rx_action+0x278/0x890 > [<000000001e81d7e6>] __do_softirq+0xd9/0x589 > [<00000000087ee354>] irq_exit+0xa2/0xc0 > [<000000001c4db0cd>] do_IRQ+0x87/0x180 > > Signed-off-by: Qian Cai > --- > net/core/dev.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/core/dev.c b/net/core/dev.c > index 522288177bbd..b898cd3036da 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -5496,6 +5496,7 @@ static void flush_backlog(struct work_struct *work) > skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp) { > if (skb->dev->reg_state == NETREG_UNREGISTERING) { > __skb_unlink(skb, &sd->input_pkt_queue); > + skb_dst_drop(skb); > kfree_skb(skb); > input_queue_head_incr(sd); > } > kfree_skb() is supposed to call skb_dst_drop() (look in skb_release_head_state()) If you think about it, we would have hundreds of similar bugs if this was not the case.