Re: general protection fault in veth_get_stats64

[Toshiaki Makita]

On 2019/10/03 5:59, Willem de Bruijn wrote:
> On Wed, Oct 2, 2019 at 3:56 PM syzbot
> <syzbot+3f3e5e77d793c7a6fe6c@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    a32db7e1 Add linux-next specific files for 20191002
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=175ab7cd600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=599cf05035799eef
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3f3e5e77d793c7a6fe6c
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12f8b943600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16981a25600000
> >
> > The bug was bisected to:
> >
> > commit 84da111de0b4be15bd500deff773f5116f39f7be
> > Author: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > Date:   Sat Sep 21 17:07:42 2019 +0000
> >
> >       Merge tag 'for-linus-hmm' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17c55847600000
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=14255847600000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=10255847600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+3f3e5e77d793c7a6fe6c@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: 84da111de0b4 ("Merge tag 'for-linus-hmm' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma")
> >
> > RSP: 002b:00007fff0ba6c998 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004424a9
> > RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
> > RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
> > R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 1 PID: 8605 Comm: syz-executor330 Not tainted 5.4.0-rc1-next-20191002
> > #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010:veth_stats_rx drivers/net/veth.c:322 [inline]
> > RIP: 0010:veth_get_stats64+0x523/0x900 drivers/net/veth.c:356
> > Code: 89 85 60 ff ff ff e8 6c 74 31 fd 49 63 c7 48 69 c0 c0 02 00 00 48 03
> > 85 60 ff ff ff 48 8d b8 a0 01 00 00 48 89 fa 48 c1 ea 03 <42> 80 3c 32 00
> > 0f 85 c9 02 00 00 48 8d b8 a8 01 00 00 48 8b 90 a0
> > RSP: 0018:ffff88809996ed00 EFLAGS: 00010202
> > RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff84418daf
> > RDX: 0000000000000034 RSI: ffffffff84418e04 RDI: 00000000000001a0
> > RBP: ffff88809996ede0 R08: ffff888093182180 R09: ffffed1013202d6a
> > R10: ffffed1013202d69 R11: ffff888099016b4f R12: 0000000000000000
> > R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
> > FS:  0000000001f4a880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000140 CR3: 000000009a80b000 CR4: 00000000001406e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >    dev_get_stats+0x8e/0x280 net/core/dev.c:9220
> >    rtnl_fill_stats+0x4d/0xac0 net/core/rtnetlink.c:1191
> >    rtnl_fill_ifinfo+0x10ad/0x3af0 net/core/rtnetlink.c:1717
> >    rtmsg_ifinfo_build_skb+0xc9/0x1a0 net/core/rtnetlink.c:3635
> >    rtmsg_ifinfo_event.part.0+0x43/0xe0 net/core/rtnetlink.c:3667
> >    rtmsg_ifinfo_event net/core/rtnetlink.c:3678 [inline]
> >    rtmsg_ifinfo+0x8d/0xa0 net/core/rtnetlink.c:3676
> >    __dev_notify_flags+0x235/0x2c0 net/core/dev.c:7757
> >    rtnl_configure_link+0x175/0x250 net/core/rtnetlink.c:2968
> >    __rtnl_newlink+0x10c4/0x16d0 net/core/rtnetlink.c:3285
> >    rtnl_newlink+0x69/0xa0 net/core/rtnetlink.c:3325
> >    rtnetlink_rcv_msg+0x463/0xb00 net/core/rtnetlink.c:5386
> >    netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
> >    rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5404
> >    netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
> >    netlink_unicast+0x531/0x710 net/netlink/af_netlink.c:1328
> >    netlink_sendmsg+0x8a5/0xd60 net/netlink/af_netlink.c:1917
> >    sock_sendmsg_nosec net/socket.c:638 [inline]
> >    sock_sendmsg+0xd7/0x130 net/socket.c:658
> >    ___sys_sendmsg+0x803/0x920 net/socket.c:2312
> >    __sys_sendmsg+0x105/0x1d0 net/socket.c:2357
> >    __do_sys_sendmsg net/socket.c:2366 [inline]
> >    __se_sys_sendmsg net/socket.c:2364 [inline]
> >    __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2364
> >    do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
> >    entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x4424a9
> > Code: e8 9c 07 03 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7
> > 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> > ff 0f 83 3b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007fff0ba6c998 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004424a9
> > RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
> > RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
> > R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000
> > Modules linked in:
> > ---[ end trace cc6dec8a4962bfff ]---
> > RIP: 0010:veth_stats_rx drivers/net/veth.c:322 [inline]
> > RIP: 0010:veth_get_stats64+0x523/0x900 drivers/net/veth.c:356
> > Code: 89 85 60 ff ff ff e8 6c 74 31 fd 49 63 c7 48 69 c0 c0 02 00 00 48 03
> > 85 60 ff ff ff 48 8d b8 a0 01 00 00 48 89 fa 48 c1 ea 03 <42> 80 3c 32 00
> > 0f 85 c9 02 00 00 48 8d b8 a8 01 00 00 48 8b 90 a0
> > RSP: 0018:ffff88809996ed00 EFLAGS: 00010202
> > RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff84418daf
> > RDX: 0000000000000034 RSI: ffffffff84418e04 RDI: 00000000000001a0
> > RBP: ffff88809996ede0 R08: ffff888093182180 R09: ffffed1013202d6a
> > R10: ffffed1013202d69 R11: ffff888099016b4f R12: 0000000000000000
> > R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
> > FS:  0000000001f4a880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000140 CR3: 000000009a80b000 CR4: 00000000001406e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>
> Syzbot CC:ed a lot of people directly on this report. Perhaps because
> of the bisection?
>
> Specific to the report: I think this may be introduced with the
> alternative names for network interfaces patchset.

Agree.

From commit ff92741270bf ("net: introduce name_node struct to be used in hashlist")

@@ -8706,6 +8761,10 @@ int register_netdevice(struct net_device *dev)
 	if (ret < 0)
 		goto out;
 
+	dev->name_node = netdev_name_node_head_alloc(dev);
+	if (!dev->name_node)
+		goto out;

This returns 0 when name_node allocation failed. This allows for creating
veth devices without calling ndo_init, thus skips rx queues allocation.

Probably need "ret = -ENOMEM" before "goto out".

> The reproducer
>
> fails on      76c9ac0ee878 net: rtnetlink: add possibility to use
> alternative names as message handle
> passes on be2644aac3e1 tcp: add ipv6_addr_v4mapped_loopback() helper
>
> Leaving
>
> 76c9ac0ee878 net: rtnetlink: add possibility to use alternative names
> as message handle
> cc6090e985d7 net: rtnetlink: introduce helper to get net_device
> instance by ifname
> 7af12cba4ef0 net: rtnetlink: unify the code in __rtnl_newlink get dev
> with the rest
> 88f4fb0c7496 net: rtnetlink: put alternative names to getlink message
> 36fbf1e52bd3 net: rtnetlink: add linkprop commands to add and delete
> alternative ifnames
> ff92741270bf net: introduce name_node struct to be used in hashlist
> 6958c97a488c net: procfs: use index hashlist instead of name hashlist
> be2

Toshiaki Makita