WARNING: refcount bug in ip6gre_tunnel

WARNING: refcount bug in ip6gre_tunnel_uninit
Status: internal: reported C repro on 2021/03/27 07:31
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: ip6_gre: proper dev_{hold|put} in ndo_[un]init methods
Patched on: [ci-upstream-bpf-next-kasan-gce ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce], missing on: [ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-upstream-bpf-kasan-gce ci-upstream-gce-leak ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce ci-upstream-kmsan-gce-386 ci-upstream-net-this-kasan-gce ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 27d, last: 24d

Cause bisection: failed (bisect log)

Sample crash report:

netlink: 24 bytes leftover after parsing attributes in process `syz-executor682'.
------------[ cut here ]------------
refcount_t: decrement hit 0; leaking memory.
WARNING: CPU: 0 PID: 8412 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31
Modules linked in:
CPU: 0 PID: 8412 Comm: syz-executor682 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31
Code: 1d 6a 5a e8 09 31 ff 89 de e8 8d 1a ab fd 84 db 75 e0 e8 d4 13 ab fd 48 c7 c7 a0 e1 c1 89 c6 05 4a 5a e8 09 01 e8 2e 36 fb 04 <0f> 0b eb c4 e8 b8 13 ab fd 0f b6 1d 39 5a e8 09 31 ff 89 de e8 58
RSP: 0018:ffffc900093cefd0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888020898000 RSI: ffffffff815c51f5 RDI: fffff52001279dec
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bdf8e R11: 0000000000000000 R12: ffff888018dda568
R13: ffff888018ddac00 R14: ffff888147ba5800 R15: ffffffff8d659b80
FS:  0000000001a0d300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055fd52caad9f CR3: 0000000025ca6000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __refcount_dec include/linux/refcount.h:344 [inline]
 refcount_dec include/linux/refcount.h:359 [inline]
 dev_put include/linux/netdevice.h:4135 [inline]
 ip6gre_tunnel_uninit+0x3d7/0x440 net/ipv6/ip6_gre.c:420
 register_netdevice+0xadf/0x1500 net/core/dev.c:10308
 ip6gre_newlink_common.constprop.0+0x158/0x410 net/ipv6/ip6_gre.c:1984
 ip6gre_newlink+0x275/0x7a0 net/ipv6/ip6_gre.c:2017
 __rtnl_newlink+0x1062/0x1710 net/core/rtnetlink.c:3443
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3491
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5553
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502
 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43f2a9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe3db0cdb8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f2a9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 0000000000403290 R08: 0000000000000070 R09: 0000000000400488
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000403320
R13: 0000000000000000 R14: 00000000004ad018 R15: 0000000000400488

Crashes (10):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-net-kasan-gce	2021/03/27 20:15	net-next	a1281601	a8529b82	.config	log	report	syz	C		WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-net-kasan-gce	2021/03/27 08:56	net-next	a1281601	a8529b82	.config	log	report	syz	C		WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-net-kasan-gce	2021/03/27 08:29	net-next	a1281601	a8529b82	.config	log	report	syz	C		WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-linux-next-kasan-gce-root	2021/03/27 15:04	linux-next	93129492	a8529b82	.config	log	report	syz	C		WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-bpf-next-kasan-gce	2021/03/30 07:11	bpf-next	7aae231a	6a81331a	.config	log	report			info	WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-net-kasan-gce	2021/03/30 02:42	net-next	37f368d8	6a81331a	.config	log	report			info	WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-net-kasan-gce	2021/03/27 07:46	net-next	a1281601	a8529b82	.config	log	report			info	WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-net-kasan-gce	2021/03/27 07:30	net-next	a1281601	a8529b82	.config	log	report			info	WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-linux-next-kasan-gce-root	2021/03/27 10:50	linux-next	93129492	a8529b82	.config	log	report			info	WARNING: refcount bug in ip6gre_tunnel_uninit
ci-upstream-linux-next-kasan-gce-root	2021/03/27 07:45	linux-next	93129492	a8529b82	.config	log	report			info	WARNING: refcount bug in ip6gre_tunnel_uninit