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Message-ID: <CANn89iKqx69Xe9x3BzDrybqwgAfiASXZ8nOC7KN8dmADonOBxw@mail.gmail.com>
Date: Tue, 20 Apr 2021 18:31:08 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Eric Dumazet <eric.dumazet@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
netdev <netdev@...r.kernel.org>,
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 Tue, Apr 20, 2021 at 5:42 PM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On Tue, Apr 20, 2021 at 04:00:07PM +0200, Eric Dumazet wrote:
> > On Tue, Apr 20, 2021 at 3:48 PM Guenter Roeck <linux@...ck-us.net> wrote:
> > >
> > > On 4/20/21 2:43 AM, Eric Dumazet wrote:
> >
> > > >
> > >
> > > 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
> >
> > OK, it would be nice if you could get line number from this stack trace.
> >
>
> Here you are:
>
> napi_gro_receive (net/core/dev.c:6196)
> receive_buf (drivers/net/virtio_net.c:1150)
> virtnet_poll (drivers/net/virtio_net.c:1414 drivers/net/virtio_net.c:1519)
> clipper_srm_device_interrupt (arch/alpha/kernel/sys_dp264.c:256)
> virtnet_poll (drivers/net/virtio_net.c:1413 drivers/net/virtio_net.c:1519)
> __napi_poll (net/core/dev.c:6962)
> net_rx_action (net/core/dev.c:7029 net/core/dev.c:7116)
> __qdisc_run (net/sched/sch_generic.c:376 net/sched/sch_generic.c:384)
> do_softirq (./include/asm-generic/softirq_stack.h:10 kernel/softirq.c:460 kernel/softirq.c:447)
> __local_bh_enable_ip (kernel/softirq.c:384)
> __dev_queue_xmit (./include/linux/bottom_half.h:32 ./include/linux/rcupdate.h:746 net/core/dev.c:4272)
> packet_sendmsg (net/packet/af_packet.c:3009 net/packet/af_packet.c:3034)
> __sys_sendto (net/socket.c:654 net/socket.c:674 net/socket.c:1977)
> __d_alloc (fs/dcache.c:1744)
> packet_create (net/packet/af_packet.c:1192 net/packet/af_packet.c:3296)
> move_addr_to_kernel (./include/linux/uaccess.h:192 net/socket.c:198 net/socket.c:192)
> __sys_sendto (net/socket.c:1968)
> sys_sendto (net/socket.c:1989 net/socket.c:1985)
> sys_bind (net/socket.c:1648 net/socket.c:1646)
> entSys (arch/alpha/kernel/entry.S:477)
>
> Guenter
OK, I guess we are back to unaligned access, right ?
I guess sh arch should have failed as well ?
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8cd76037c72481200ea3e8429e9fdfec005dad85..0579914d3dd84c24982c1ff85314cc7b8d0f8d2d
100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -415,7 +415,8 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- if (len > GOOD_COPY_LEN && tailroom >= shinfo_size) {
+ if (len > GOOD_COPY_LEN && tailroom >= shinfo_size &&
+ (!NET_IP_ALIGN || ((unsigned long)p & 3) == 2)) {
skb = build_skb(p, truesize);
if (unlikely(!skb))
return NULL;
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