Re: [PATCH net v2 3/4] bonding: restore bond's IFF_SLAVE flag if a non-eth dev enslave fails

[Michal Kubiak <michal.kubiak@intel.com>]

On Tue, Mar 14, 2023 at 01:14:25PM +0200, Nikolay Aleksandrov wrote:
> syzbot reported a warning[1] where the bond device itself is a slave and
> we try to enslave a non-ethernet device as the first slave which fails
> but then in the error path when ether_setup() restores the bond device
> it also clears all flags. In my previous fix[2] I restored the
> IFF_MASTER flag, but I didn't consider the case that the bond device
> itself might also be a slave with IFF_SLAVE set, so we need to restore
> that flag as well. Use the new bond_ether_setup helper which does the
> right thing and restores the bond's flags properly.
> 
> Steps to reproduce using a nlmon dev:
>  $ ip l add nlmon0 type nlmon
>  $ ip l add bond1 type bond
>  $ ip l add bond2 type bond
>  $ ip l set bond1 master bond2
>  $ ip l set dev nlmon0 master bond1
>  $ ip -d l sh dev bond1
>  22: bond1: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noqueue master bond2 state DOWN mode DEFAULT group default qlen 1000
>  (now bond1's IFF_SLAVE flag is gone and we'll hit a warning[3] if we
>   try to delete it)
> 
> [1] https://syzkaller.appspot.com/bug?id=391c7b1f6522182899efba27d891f1743e8eb3ef
> [2] commit 7d5cd2ce5292 ("bonding: correctly handle bonding type change on enslave failure")
> [3] example warning:
>  [   27.008664] bond1: (slave nlmon0): The slave device specified does not support setting the MAC address
>  [   27.008692] bond1: (slave nlmon0): Error -95 calling set_mac_address
>  [   32.464639] bond1 (unregistering): Released all slaves
>  [   32.464685] ------------[ cut here ]------------
>  [   32.464686] WARNING: CPU: 1 PID: 2004 at net/core/dev.c:10829 unregister_netdevice_many+0x72a/0x780
>  [   32.464694] Modules linked in: br_netfilter bridge bonding virtio_net
>  [   32.464699] CPU: 1 PID: 2004 Comm: ip Kdump: loaded Not tainted 5.18.0-rc3+ #47
>  [   32.464703] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.1-2.fc37 04/01/2014
>  [   32.464704] RIP: 0010:unregister_netdevice_many+0x72a/0x780
>  [   32.464707] Code: 99 fd ff ff ba 90 1a 00 00 48 c7 c6 f4 02 66 96 48 c7 c7 20 4d 35 96 c6 05 fa c7 2b 02 01 e8 be 6f 4a 00 0f 0b e9 73 fd ff ff <0f> 0b e9 5f fd ff ff 80 3d e3 c7 2b 02 00 0f 85 3b fd ff ff ba 59
>  [   32.464710] RSP: 0018:ffffa006422d7820 EFLAGS: 00010206
>  [   32.464712] RAX: ffff8f6e077140a0 RBX: ffffa006422d7888 RCX: 0000000000000000
>  [   32.464714] RDX: ffff8f6e12edbe58 RSI: 0000000000000296 RDI: ffffffff96d4a520
>  [   32.464716] RBP: ffff8f6e07714000 R08: ffffffff96d63600 R09: ffffa006422d7728
>  [   32.464717] R10: 0000000000000ec0 R11: ffffffff9698c988 R12: ffff8f6e12edb140
>  [   32.464719] R13: dead000000000122 R14: dead000000000100 R15: ffff8f6e12edb140
>  [   32.464723] FS:  00007f297c2f1740(0000) GS:ffff8f6e5d900000(0000) knlGS:0000000000000000
>  [   32.464725] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  [   32.464726] CR2: 00007f297bf1c800 CR3: 00000000115e8000 CR4: 0000000000350ee0
>  [   32.464730] Call Trace:
>  [   32.464763]  <TASK>
>  [   32.464767]  rtnl_dellink+0x13e/0x380
>  [   32.464776]  ? cred_has_capability.isra.0+0x68/0x100
>  [   32.464780]  ? __rtnl_unlock+0x33/0x60
>  [   32.464783]  ? bpf_lsm_capset+0x10/0x10
>  [   32.464786]  ? security_capable+0x36/0x50
>  [   32.464790]  rtnetlink_rcv_msg+0x14e/0x3b0
>  [   32.464792]  ? _copy_to_iter+0xb1/0x790
>  [   32.464796]  ? post_alloc_hook+0xa0/0x160
>  [   32.464799]  ? rtnl_calcit.isra.0+0x110/0x110
>  [   32.464802]  netlink_rcv_skb+0x50/0xf0
>  [   32.464806]  netlink_unicast+0x216/0x340
>  [   32.464809]  netlink_sendmsg+0x23f/0x480
>  [   32.464812]  sock_sendmsg+0x5e/0x60
>  [   32.464815]  ____sys_sendmsg+0x22c/0x270
>  [   32.464818]  ? import_iovec+0x17/0x20
>  [   32.464821]  ? sendmsg_copy_msghdr+0x59/0x90
>  [   32.464823]  ? do_set_pte+0xa0/0xe0
>  [   32.464828]  ___sys_sendmsg+0x81/0xc0
>  [   32.464832]  ? mod_objcg_state+0xc6/0x300
>  [   32.464835]  ? refill_obj_stock+0xa9/0x160
>  [   32.464838]  ? memcg_slab_free_hook+0x1a5/0x1f0
>  [   32.464842]  __sys_sendmsg+0x49/0x80
>  [   32.464847]  do_syscall_64+0x3b/0x90
>  [   32.464851]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>  [   32.464865] RIP: 0033:0x7f297bf2e5e7
>  [   32.464868] Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10
>  [   32.464869] RSP: 002b:00007ffd96c824c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
>  [   32.464872] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f297bf2e5e7
>  [   32.464874] RDX: 0000000000000000 RSI: 00007ffd96c82540 RDI: 0000000000000003
>  [   32.464875] RBP: 00000000640f19de R08: 0000000000000001 R09: 000000000000007c
>  [   32.464876] R10: 00007f297bffabe0 R11: 0000000000000246 R12: 0000000000000001
>  [   32.464877] R13: 00007ffd96c82d20 R14: 00007ffd96c82610 R15: 000055bfe38a7020
>  [   32.464881]  </TASK>
>  [   32.464882] ---[ end trace 0000000000000000 ]---
> 
> Fixes: 7d5cd2ce5292 ("bonding: correctly handle bonding type change on enslave failure")
> Reported-by: syzbot+9dfc3f3348729cc82277@syzkaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?id=391c7b1f6522182899efba27d891f1743e8eb3ef
> Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>

Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>