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Message-ID: <c5a8aeaf-0f41-9274-b9c5-ec385b34180a@roeck-us.net>
Date: Tue, 20 Apr 2021 06:48:22 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Eric Dumazet <eric.dumazet@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
syzbot <syzkaller@...glegroups.com>,
Mat Martineau <mathew.j.martineau@...ux.intel.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
Jason Wang <jasowang@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next] virtio-net: fix use-after-free in page_to_skb()
On 4/20/21 2:43 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> KASAN/syzbot had 4 reports, one of them being:
>
> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:191 [inline]
> BUG: KASAN: slab-out-of-bounds in page_to_skb+0x5cf/0xb70 drivers/net/virtio_net.c:480
> Read of size 12 at addr ffff888014a5f800 by task systemd-udevd/8445
>
> CPU: 0 PID: 8445 Comm: systemd-udevd Not tainted 5.12.0-rc8-next-20210419-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <IRQ>
> __dump_stack lib/dump_stack.c:79 [inline]
> dump_stack+0x141/0x1d7 lib/dump_stack.c:120
> print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:233
> __kasan_report mm/kasan/report.c:419 [inline]
> kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:436
> check_region_inline mm/kasan/generic.c:180 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:186
> memcpy+0x20/0x60 mm/kasan/shadow.c:65
> memcpy include/linux/fortify-string.h:191 [inline]
> page_to_skb+0x5cf/0xb70 drivers/net/virtio_net.c:480
> receive_mergeable drivers/net/virtio_net.c:1009 [inline]
> receive_buf+0x2bc0/0x6250 drivers/net/virtio_net.c:1119
> virtnet_receive drivers/net/virtio_net.c:1411 [inline]
> virtnet_poll+0x568/0x10b0 drivers/net/virtio_net.c:1516
> __napi_poll+0xaf/0x440 net/core/dev.c:6962
> napi_poll net/core/dev.c:7029 [inline]
> net_rx_action+0x801/0xb40 net/core/dev.c:7116
> __do_softirq+0x29b/0x9fe kernel/softirq.c:559
> invoke_softirq kernel/softirq.c:433 [inline]
> __irq_exit_rcu+0x136/0x200 kernel/softirq.c:637
> irq_exit_rcu+0x5/0x20 kernel/softirq.c:649
> common_interrupt+0xa4/0xd0 arch/x86/kernel/irq.c:240
>
> Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Reported-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
> Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: virtualization@...ts.linux-foundation.org
> ---
> drivers/net/virtio_net.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 8cd76037c72481200ea3e8429e9fdfec005dad85..2e28c04aa6351d2b4016f7d277ce104c4970069d 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -385,6 +385,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> struct sk_buff *skb;
> struct virtio_net_hdr_mrg_rxbuf *hdr;
> unsigned int copy, hdr_len, hdr_padded_len;
> + struct page *page_to_free = NULL;
> int tailroom, shinfo_size;
> char *p, *hdr_p;
>
> @@ -445,7 +446,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> if (len)
> skb_add_rx_frag(skb, 0, page, offset, len, truesize);
> else
> - put_page(page);
> + page_to_free = page;
> goto ok;
> }
>
> @@ -479,6 +480,8 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> hdr = skb_vnet_hdr(skb);
> memcpy(hdr, hdr_p, hdr_len);
> }
> + if (page_to_free)
> + put_page(page_to_free);
>
> if (metasize) {
> __skb_pull(skb, metasize);
>
Unfortunately that doesn't fix the problem for me. With this patch applied
on top of next-20210419, I still get the same crash as before:
udhcpc: sending discover^M
Unable to handle kernel paging request at virtual address 0000000000000004^M
udhcpc(169): Oops -1^M
pc = [<0000000000000004>] ra = [<fffffc0000b8c5b8>] ps = 0000 Not tainted^M
pc is at 0x4^M
ra is at napi_gro_receive+0x68/0x150^M
v0 = 0000000000000000 t0 = 0000000000000008 t1 = 0000000000000000^M
t2 = 0000000000000000 t3 = 000000000000000e t4 = 0000000000000038^M
t5 = 000000000000ffff t6 = fffffc00002f298a t7 = fffffc0002c78000^M
s0 = fffffc00010b3ca0 s1 = 0000000000000000 s2 = fffffc00011267e0^M
s3 = 0000000000000000 s4 = fffffc00025f2008 s5 = fffffc00002f2940^M
s6 = fffffc00025f2040^M
a0 = fffffc00025f2008 a1 = fffffc00002f2940 a2 = fffffc0002ca000c^M
a3 = fffffc00000250d0 a4 = 0000000effff0008 a5 = 0000000000000000^M
t8 = fffffc00010b3c80 t9 = fffffc0002ca04cc t10= 0000000000000000^M
t11= 00000000000004c0 pv = fffffc0000b8bc40 at = 0000000000000000^M
gp = fffffc00010f9fb8 sp = 00000000df74db09^M
Disabling lock debugging due to kernel taint^M
Trace:^M
[<fffffc0000b8c5b8>] napi_gro_receive+0x68/0x150^M
[<fffffc00009b409c>] receive_buf+0x50c/0x1b80^M
[<fffffc00009b58b8>] virtnet_poll+0x1a8/0x5b0^M
[<fffffc00009b58ec>] virtnet_poll+0x1dc/0x5b0^M
[<fffffc0000b8d17c>] __napi_poll+0x4c/0x270^M
[<fffffc0000b8d670>] net_rx_action+0x130/0x2c0^M
[<fffffc0000bd6cb0>] sch_direct_xmit+0x170/0x360^M
[<fffffc0000bd7000>] __qdisc_run+0x160/0x6c0^M
[<fffffc0000337b64>] do_softirq+0xa4/0xd0^M
[<fffffc0000337ca4>] __local_bh_enable_ip+0x114/0x120^M
[<fffffc0000b89554>] __dev_queue_xmit+0x484/0xa60^M
[<fffffc0000cd072c>] packet_sendmsg+0xe7c/0x1ba0^M
[<fffffc0000b53338>] __sys_sendto+0xf8/0x170^M
[<fffffc0000cfec18>] _raw_spin_unlock+0x18/0x30^M
[<fffffc0000a9bf7c>] ehci_irq+0x2cc/0x5c0^M
[<fffffc0000a71334>] usb_hcd_irq+0x34/0x50^M
[<fffffc0000b521bc>] move_addr_to_kernel+0x3c/0x60^M
[<fffffc0000b532e4>] __sys_sendto+0xa4/0x170^M
[<fffffc0000b533d4>] sys_sendto+0x24/0x40^M
[<fffffc0000cfea38>] _raw_spin_lock+0x18/0x30^M
[<fffffc0000cfec18>] _raw_spin_unlock+0x18/0x30^M
[<fffffc0000325298>] clipper_enable_irq+0x98/0x100^M
[<fffffc0000cfec18>] _raw_spin_unlock+0x18/0x30^M
[<fffffc0000311514>] entSys+0xa4/0xc0^M
^M
Code:^M
00000000 ^M
00063301 ^M
00000897 ^M
00001111 ^M
00001672 ^M
^M
Kernel panic - not syncing: Aiee, killing interrupt handler!^M
Guenter
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