Re: [PATCH v8 34/50] vhost/net: virtio 1.0 byte swap

[Michael S. Tsirkin]

On Wed, Jan 07, 2015 at 09:31:05AM +0100, Greg Kurz wrote:
> On Tue, 06 Jan 2015 16:55:30 -0700
> Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
> 
> > On Mon, 2014-12-01 at 18:05 +0200, Michael S. Tsirkin wrote:
> > > I had to add an explicit tag to suppress compiler warning:
> > > gcc isn't smart enough to notice that
> > > len is always initialized since function is called with size > 0.
> > 
> > I'm getting a panic inside a guest when this change is applied on the
> > host.  I identified this patch via bisect and confirmed by reverting it
> > from v3.19-rc2.  Guest is centos6.  Thanks,
> > 
> > Alex
> > 
> > commit 8b38694a2dc8b18374310df50174f1e4376d6824
> > Author: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > Date:   Fri Oct 24 14:19:48 2014 +0300
> > 
> >     vhost/net: virtio 1.0 byte swap
> >     
> >     I had to add an explicit tag to suppress compiler warning:
> >     gcc isn't smart enough to notice that
> >     len is always initialized since function is called with size > 0.
> >     
> >     Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> >     Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
> > 
> 
> This chunk looks suspicious:
> 
> -	heads[headcount - 1].len += datalen;
> +	heads[headcount - 1].len = cpu_to_vhost32(vq, len - datalen);
> 
> s/len - datalen/len + datalen/ ?

Indeed!
I just sent a patch fixing this, thanks a lot.


> > XML chunk:
> > 
> >     <interface type='direct'>
> >       <mac address='52:54:00:64:f3:34'/>
> >       <source dev='iscsinet0' mode='bridge'/>
> >       <model type='virtio'/>
> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
> >     </interface>
> > 
> > Panic log:
> > 
> > <1>BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> > <1>IP: [<ffffffffa0079469>] virtnet_poll+0x4f9/0x910 [virtio_net]
> > <4>PGD 1aa2f4067 PUD 1aa2f5067 PMD 0 
> > <4>Oops: 0000 [#1] SMP 
> > <4>last sysfs file: /sys/devices/pci0000:00/0000:00:03.0/virtio0/net/eth9/ifindex
> > <4>CPU 0 
> > <4>Modules linked in: 8021q garp stp llc ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 uinput microcode snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore snd_page_alloc igbvf nvidia(P)(U) i2c_core tg3 ptp pps_core virtio_balloon virtio_net virtio_console ext4 jbd2 mbcache virtio_blk virtio_pci virtio_ring virtio pata_acpi ata_generic ata_piix dm_mirror dm_region_hash dm_log dm_mod [last unloaded: speedstep_lib]
> > <4>
> > <4>Pid: 1374, comm: NetworkManager Tainted: P           ---------------    2.6.32-431.23.3.el6.centos.plus.x86_64 #1 QEMU Standard PC (i440FX + PIIX, 1996)
> > <4>RIP: 0010:[<ffffffffa0079469>]  [<ffffffffa0079469>] virtnet_poll+0x4f9/0x910 [virtio_net]
> > <4>RSP: 0018:ffff880028203e48  EFLAGS: 00010246
> > <4>RAX: ffff8801a3383d00 RBX: ffff8801a6aaf480 RCX: ffff8801aa20b6e0
> > <4>RDX: 00000000000000c0 RSI: ffff8801a3383c00 RDI: ffff8801a3383cc0
> > <4>RBP: ffff880028203ed8 R08: 000000000000009e R09: ffff8801aa1d800c
> > <4>R10: 0000000000000218 R11: 0000000000000000 R12: ffff8801aa20b6e0
> > <4>R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> > <4>FS:  00007febf114d800(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
> > <4>CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > <4>CR2: 0000000000000010 CR3: 00000001aa793000 CR4: 00000000000006f0
> > <4>DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > <4>DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > <4>Process NetworkManager (pid: 1374, threadinfo ffff8801a74ba000, task ffff8801a8d56040)
> > <4>Stack:
> > <4> ffff8801aa1d8000 000000000000009e ffff8801aa20b6e0 ffff8801aa20b718
> > <4><d> ffff8801aa20b780 ffff8801aa1d800c ffff8801a6aaf4b8 ffff8801aa20b020
> > <4><d> 0000000000000080 ffff8801aa20b708 0000000000000001 00001f5981a830c8
> > <4>Call Trace:
> > <4> <IRQ> 
> > <4> [<ffffffff8146ae33>] net_rx_action+0x103/0x2f0
> > <4> [<ffffffff8107a5f1>] __do_softirq+0xc1/0x1e0
> > <4> [<ffffffff8100c30c>] ? call_softirq+0x1c/0x30
> > <4> [<ffffffff8100c30c>] call_softirq+0x1c/0x30
> > <4> <EOI> 
> > <4> [<ffffffff8100fa75>] ? do_softirq+0x65/0xa0
> > <4> [<ffffffff8107b2ea>] local_bh_enable+0x9a/0xb0
> > <4> [<ffffffffa007813a>] virtnet_napi_enable+0x4a/0x60 [virtio_net]
> > <4> [<ffffffffa0078ebf>] virtnet_open+0x4f/0x60 [virtio_net]
> > <4> [<ffffffff81467691>] dev_open+0xa1/0x100
> > <4> [<ffffffff81466751>] dev_change_flags+0xa1/0x1d0
> > <4> [<ffffffff81474a59>] do_setlink+0x169/0x8b0
> > <4> [<ffffffff814770b6>] ? rtnl_fill_ifinfo+0x946/0xcb0
> > <4> [<ffffffff812a3d24>] ? nla_parse+0x34/0x110
> > <4> [<ffffffff8147659e>] rtnl_setlink+0xee/0x130
> > <4> [<ffffffff81475b67>] rtnetlink_rcv_msg+0x2d7/0x340
> > <4> [<ffffffff81231e14>] ? socket_has_perm+0x74/0x90
> > <4> [<ffffffff81475890>] ? rtnetlink_rcv_msg+0x0/0x340
> > <4> [<ffffffff814910a9>] netlink_rcv_skb+0xa9/0xd0
> > <4> [<ffffffff81475875>] rtnetlink_rcv+0x25/0x40
> > <4> [<ffffffff81490cdb>] netlink_unicast+0x2db/0x320
> > <4> [<ffffffff81491750>] netlink_sendmsg+0x2c0/0x3d0
> > <4> [<ffffffff814520c3>] sock_sendmsg+0x123/0x150
> > <4> [<ffffffff81453d73>] ? sock_recvmsg+0x133/0x160
> > <4> [<ffffffff8109afa0>] ? autoremove_wake_function+0x0/0x40
> > <4> [<ffffffff81136941>] ? lru_cache_add_lru+0x21/0x40
> > <4> [<ffffffff8115522d>] ? page_add_new_anon_rmap+0x9d/0xf0
> > <4> [<ffffffff8114aeef>] ? handle_pte_fault+0x4af/0xb00
> > <4> [<ffffffff81451f14>] ? move_addr_to_kernel+0x64/0x70
> > <4> [<ffffffff814538b6>] __sys_sendmsg+0x406/0x420
> > <4> [<ffffffff8104a98c>] ? __do_page_fault+0x1ec/0x480
> > <4> [<ffffffff814523d9>] ? sys_sendto+0x139/0x190
> > <4> [<ffffffff8103ea6c>] ? kvm_clock_read+0x1c/0x20
> > <4> [<ffffffff81453ad9>] sys_sendmsg+0x49/0x90
> > <4> [<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
> > <4>Code: 83 e0 00 00 00 00 10 00 00 48 03 93 d0 00 00 00 66 83 42 04 01 8b 93 cc 00 00 00 48 8b b3 d0 00 00 00 80 4c 16 10 20 44 2b 68 0c <4d> 8b 76 10 75 89 e9 d1 fd ff ff 0f 1f 40 00 a8 02 74 0d 0f b6 
> > <1>RIP  [<ffffffffa0079469>] virtnet_poll+0x4f9/0x910 [virtio_net]
> > <4> RSP <ffff880028203e48>
> > <4>CR2: 0000000000000010
> > 
> > 
> > _______________________________________________
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> > https://lists.linuxfoundation.org/mailman/listinfo/virtualization
> > 
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