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Message-ID: <aa55b487-44bb-1596-d310-9b74b9ba47fe@redhat.com>
Date: Tue, 20 Apr 2021 10:38:08 +0800
From: Jason Wang <jasowang@...hat.com>
To: Mat Martineau <mathew.j.martineau@...ux.intel.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next v3] virtio-net: page_to_skb() use build_skb when
there's sufficient tailroom
在 2021/4/20 上午7:29, Mat Martineau 写道:
>
> On Fri, 16 Apr 2021, Xuan Zhuo wrote:
>
>> In page_to_skb(), if we have enough tailroom to save skb_shared_info, we
>> can use build_skb to create skb directly. No need to alloc for
>> additional space. And it can save a 'frags slot', which is very friendly
>> to GRO.
>>
>> Here, if the payload of the received package is too small (less than
>> GOOD_COPY_LEN), we still choose to copy it directly to the space got by
>> napi_alloc_skb. So we can reuse these pages.
>>
>> Testing Machine:
>> The four queues of the network card are bound to the cpu1.
>>
>> Test command:
>> for ((i=0;i<5;++i)); do sockperf tp --ip 192.168.122.64 -m 1000 -t
>> 150& done
>>
>> The size of the udp package is 1000, so in the case of this patch, there
>> will always be enough tailroom to use build_skb. The sent udp packet
>> will be discarded because there is no port to receive it. The irqsoftd
>> of the machine is 100%, we observe the received quantity displayed by
>> sar -n DEV 1:
>>
>> no build_skb: 956864.00 rxpck/s
>> build_skb: 1158465.00 rxpck/s
>>
>> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>> Suggested-by: Jason Wang <jasowang@...hat.com>
>> ---
>>
>> v3: fix the truesize when headroom > 0
>>
>> v2: conflict resolution
>>
>> drivers/net/virtio_net.c | 69 ++++++++++++++++++++++++++++------------
>> 1 file changed, 48 insertions(+), 21 deletions(-)
>
> Xuan,
>
> I realize this has been merged to net-next already, but I'm getting a
> use-after-free with KASAN in page_to_skb() with this patch. Reverting
> this change fixes the UAF. I've included the KASAN dump below, and a
> couple of comments inline.
>
>
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 101659cd4b87..8cd76037c724 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -379,21 +379,17 @@ static struct sk_buff *page_to_skb(struct
>> virtnet_info *vi,
>> struct receive_queue *rq,
>> struct page *page, unsigned int offset,
>> unsigned int len, unsigned int truesize,
>> - bool hdr_valid, unsigned int metasize)
>> + bool hdr_valid, unsigned int metasize,
>> + unsigned int headroom)
>> {
>> struct sk_buff *skb;
>> struct virtio_net_hdr_mrg_rxbuf *hdr;
>> unsigned int copy, hdr_len, hdr_padded_len;
>> - char *p;
>> + int tailroom, shinfo_size;
>> + char *p, *hdr_p;
>>
>> p = page_address(page) + offset;
>> -
>> - /* copy small packet so we can reuse these pages for small data */
>> - skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN);
>> - if (unlikely(!skb))
>> - return NULL;
>> -
>> - hdr = skb_vnet_hdr(skb);
>> + hdr_p = p;
>
> hdr_p is assigned here, pointer to an address in the provided page...
>
>>
>> hdr_len = vi->hdr_len;
>> if (vi->mergeable_rx_bufs)
>
> (snip)
>
>> @@ -431,7 +446,7 @@ static struct sk_buff *page_to_skb(struct
>> virtnet_info *vi,
>> skb_add_rx_frag(skb, 0, page, offset, len, truesize);
>> else
>> put_page(page);
>
> page is potentially released here...
>
>> - return skb;
>> + goto ok;
>> }
>>
>> /*
>> @@ -458,6 +473,18 @@ static struct sk_buff *page_to_skb(struct
>> virtnet_info *vi,
>> if (page)
>> give_pages(rq, page);
>>
>> +ok:
>> + /* hdr_valid means no XDP, so we can copy the vnet header */
>> + if (hdr_valid) {
>> + hdr = skb_vnet_hdr(skb);
>> + memcpy(hdr, hdr_p, hdr_len);
>
> and hdr_p is dereferenced here.
Right, I tend to recover the way to copy hdr and set meta just after
alloc/build_skb().
Thanks
>
> I'm seeing this KASAN UAF at boot time in a kvm VM (Fedora 33 host and
> guest, if that helps):
>
> [ 61.202483]
> ==================================================================
> [ 61.204005] BUG: KASAN: use-after-free in page_to_skb+0x32a/0x4b0
> [ 61.205387] Read of size 12 at addr ffff888105bdf800 by task
> NetworkManager/579
> [ 61.207035] [ 61.207408] CPU: 0 PID: 579 Comm: NetworkManager Not
> tainted 5.12.0-rc7+ #2
> [ 61.208715] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.14.0-1.fc33 04/01/2014
> [ 61.210257] Call Trace:
> [ 61.210730] <IRQ>
> [ 61.211209] dump_stack+0x93/0xc2
> [ 61.211996] print_address_description.constprop.0+0x18/0x130
> [ 61.213310] ? page_to_skb+0x32a/0x4b0
> [ 61.214318] ? page_to_skb+0x32a/0x4b0
> [ 61.215085] kasan_report.cold+0x7f/0x111
> [ 61.215966] ? trace_hardirqs_off+0x10/0xe0
> [ 61.216823] ? page_to_skb+0x32a/0x4b0
> [ 61.217809] kasan_check_range+0xf9/0x1e0
> [ 61.217834] memcpy+0x20/0x60
> [ 61.217848] page_to_skb+0x32a/0x4b0
> [ 61.217888] receive_buf+0x1434/0x2690
> [ 61.217926] ? page_to_skb+0x4b0/0x4b0
> [ 61.217947] ? find_held_lock+0x85/0xa0
> [ 61.217964] ? lock_release+0x1d0/0x400
> [ 61.217974] ? virtnet_poll+0x1d8/0x6b0
> [ 61.217983] ? detach_buf_split+0x254/0x290
> [ 61.218008] ? virtqueue_get_buf_ctx_split+0x145/0x1f0
> [ 61.218032] virtnet_poll+0x2a8/0x6b0
> [ 61.218057] ? receive_buf+0x2690/0x2690
> [ 61.218067] ? lock_release+0x400/0x400
> [ 61.218119] __napi_poll+0x57/0x2f0
> [ 61.229624] net_rx_action+0x4dd/0x590
> [ 61.230453] ? napi_threaded_poll+0x2b0/0x2b0
> [ 61.231379] ? rcu_implicit_dynticks_qs+0x430/0x430
> [ 61.232429] ? lock_is_held_type+0x98/0x110
> [ 61.233342] __do_softirq+0xfd/0x59d
> [ 61.234131] do_softirq+0x8a/0xb0
> [ 61.234896] </IRQ>
> [ 61.235397] ? virtnet_open+0x10a/0x2e0
> [ 61.236273] __local_bh_enable_ip+0xb1/0xc0
> [ 61.237199] virtnet_open+0x11b/0x2e0
> [ 61.237981] __dev_open+0x1b7/0x2c0
> [ 61.238689] ? dev_set_rx_mode+0x60/0x60
> [ 61.239499] ? lockdep_hardirqs_on_prepare+0x12e/0x1f0
> [ 61.240523] ? __local_bh_enable_ip+0x7b/0xc0
> [ 61.241399] ? trace_hardirqs_on+0x1c/0x100
> [ 61.242248] __dev_change_flags+0x2e6/0x370
> [ 61.243098] ? dev_set_allmulti+0x10/0x10
> [ 61.243908] ? lock_chain_count+0x20/0x20
> [ 61.244759] dev_change_flags+0x55/0xb0
> [ 61.245595] do_setlink+0xb52/0x1950
> [ 61.246385] ? rtnl_getlink+0x560/0x560
> [ 61.247218] ? mark_lock+0x101/0x19c0
> [ 61.248003] ? lock_chain_count+0x20/0x20
> [ 61.248864] ? lock_chain_count+0x20/0x20
> [ 61.249728] ? lockdep_hardirqs_on_prepare+0x1f0/0x1f0
> [ 61.250821] ? memset+0x20/0x40
> [ 61.251474] ? __nla_validate_parse+0xac/0x12f0
> [ 61.252433] ? nla_get_range_signed+0x1c0/0x1c0
> [ 61.253409] ? __lock_acquire+0x85f/0x3090
> [ 61.254291] __rtnl_newlink+0x85f/0xca0
> [ 61.255131] ? rtnl_setlink+0x220/0x220
> [ 61.255988] ? lock_is_held_type+0x98/0x110
> [ 61.256911] ? find_held_lock+0x85/0xa0
> [ 61.257782] ? __is_insn_slot_addr+0xa5/0x130
> [ 61.257794] ? lock_downgrade+0x390/0x390
> [ 61.257802] ? stack_access_ok+0x35/0x90
> [ 61.257818] ? entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 61.257840] ? __is_insn_slot_addr+0xc4/0x130
> [ 61.257859] ? kernel_text_address+0xc8/0xf0
> [ 61.257876] ? __kernel_text_address+0x9/0x30
> [ 61.257885] ? unwind_get_return_address+0x2a/0x40
> [ 61.257893] ? create_prof_cpu_mask+0x20/0x20
> [ 61.257903] ? arch_stack_walk+0x99/0xf0
> [ 61.258007] ? lock_release+0x1d0/0x400
> [ 61.258016] ? fs_reclaim_release+0x56/0x90
> [ 61.258027] ? lock_downgrade+0x390/0x390
> [ 61.258036] ? find_held_lock+0x80/0xa0
> [ 61.258049] ? lock_release+0x1d0/0x400
> [ 61.258059] ? lock_is_held_type+0x98/0x110
> [ 61.258087] rtnl_newlink+0x4b/0x70
> [ 61.258099] rtnetlink_rcv_msg+0x22c/0x5e0
> [ 61.258116] ? rtnetlink_put_metrics+0x2c0/0x2c0
> [ 61.258131] ? lock_acquire+0x157/0x4d0
> [ 61.258140] ? netlink_deliver_tap+0xa6/0x570
> [ 61.258154] ? lock_release+0x400/0x400
> [ 61.258172] netlink_rcv_skb+0xc4/0x1f0
> [ 61.258180] ? rtnetlink_put_metrics+0x2c0/0x2c0
> [ 61.258193] ? netlink_ack+0x4f0/0x4f0
> [ 61.258199] ? netlink_deliver_tap+0x129/0x570
> [ 61.258234] netlink_unicast+0x2d3/0x410
> [ 61.258248] ? netlink_attachskb+0x400/0x400
> [ 61.258257] ? _copy_from_iter_full+0xd8/0x360
> [ 61.258280] netlink_sendmsg+0x394/0x670
> [ 61.258299] ? netlink_unicast+0x410/0x410
> [ 61.258305] ? iovec_from_user+0xa1/0x1d0
> [ 61.258327] ? netlink_unicast+0x410/0x410
> [ 61.258340] sock_sendmsg+0x91/0xa0
> [ 61.258353] ____sys_sendmsg+0x3b7/0x400
> [ 61.258366] ? kernel_sendmsg+0x30/0x30
> [ 61.258376] ? __ia32_sys_recvmmsg+0x150/0x150
> [ 61.258390] ? lockdep_hardirqs_on_prepare+0x1f0/0x1f0
> [ 61.258398] ? stack_trace_save+0x8c/0xc0
> [ 61.258408] ? stack_trace_consume_entry+0x80/0x80
> [ 61.258416] ? __fput+0x1a9/0x3d0
> [ 61.258435] ___sys_sendmsg+0xd3/0x130
> [ 61.258446] ? sendmsg_copy_msghdr+0x110/0x110
> [ 61.258458] ? find_held_lock+0x85/0xa0
> [ 61.258471] ? lock_release+0x1d0/0x400
> [ 61.258479] ? __fget_files+0x133/0x210
> [ 61.258490] ? lock_downgrade+0x390/0x390
> [ 61.258508] ? lockdep_hardirqs_on_prepare+0x1f0/0x1f0
> [ 61.258529] ? __fget_files+0x152/0x210
> [ 61.258547] ? __fget_light+0x66/0xf0
> [ 61.258568] __sys_sendmsg+0xae/0x120
> [ 61.258578] ? __sys_sendmsg_sock+0x10/0x10
> [ 61.258589] ? lockdep_hardirqs_on_prepare+0x12e/0x1f0
> [ 61.258598] ? call_rcu+0x414/0x670
> [ 61.258616] ? mark_held_locks+0x25/0x90
> [ 61.258630] ? lockdep_hardirqs_on_prepare+0x12e/0x1f0
> [ 61.258639] ? syscall_enter_from_user_mode+0x1d/0x50
> [ 61.258647] ? trace_hardirqs_on+0x1c/0x100
> [ 61.258662] do_syscall_64+0x33/0x40
> [ 61.258670] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 61.258679] RIP: 0033:0x7fb33db83ecd
> [ 61.258686] Code: 28 89 54 24 1c 48 89 74 24 10 89 7c 24 08 e8 4a
> ee ff ff 8b 54 24 1c 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 2e 00 00
> 00 0f 05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 44 24 08 e8 9e ee ff
> ff 48
> [ 61.258692] RSP: 002b:00007ffc85e90e30 EFLAGS: 00000293 ORIG_RAX:
> 000000000000002e
> [ 61.258702] RAX: ffffffffffffffda RBX: 000055f87a7aa030 RCX:
> 00007fb33db83ecd
> [ 61.258708] RDX: 0000000000000000 RSI: 00007ffc85e90e70 RDI:
> 000000000000000c
> [ 61.258713] RBP: 000000000000000c R08: 0000000000000000 R09:
> 0000000000000000
> [ 61.258717] R10: 0000000000000000 R11: 0000000000000293 R12:
> 0000000000000000
> [ 61.258722] R13: 00007ffc85e90fd0 R14: 00007ffc85e90fcc R15:
> 0000000000000000
>
>
> --
> Mat Martineau
> Intel
>
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