bisecting cause commit starting from 90568ecf561540fa330511e21fcd823b0c3829c6
building syzkaller on 06150bf1b39b70e521560bc943ac19b281903ebc
testing commit 90568ecf561540fa330511e21fcd823b0c3829c6 with gcc (GCC) 8.1.0
kernel signature: 46f02d6ee6ba1e53cb1783a4fafd29e1aed4ea6657dc28aa34a0edbc9782c0b1
run #0: crashed: WARNING: refcount bug in l2cap_chan_put
run #1: crashed: WARNING: refcount bug in l2cap_chan_put
run #2: crashed: WARNING: refcount bug in l2cap_chan_put
run #3: crashed: WARNING: refcount bug in l2cap_chan_put
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: WARNING: refcount bug in l2cap_chan_put
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: OK
testing release v5.5
testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 with gcc (GCC) 8.1.0
kernel signature: fb119f0b5291aa825df83c2137e7a20c4c58d2b4d9d51e0bffc5f265b70d3f21
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: WARNING: refcount bug in l2cap_chan_put
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: WARNING: refcount bug in l2cap_chan_put
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v5.4
testing commit 219d54332a09e8d8741c1e1982f5eae56099de85 with gcc (GCC) 8.1.0
kernel signature: 997a8a2cb60cc1794e99a1a1a6d77a93e54288ae027c4bbe90ee7b626b836e06
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v5.3
testing commit 4d856f72c10ecb060868ed10ff1b1453943fc6c8 with gcc (GCC) 8.1.0
kernel signature: e5eaa67a8f70c174b07e8854717af4fc0558777625e44873e878953870221909
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: boot failed: BUG: spinlock bad magic in nf_connlabels_get
testing release v5.2
testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 with gcc (GCC) 8.1.0
kernel signature: bf66c80f9e2469dd7ad8fff29790b238ebef3eacf19b9654b42aa83918e6d710
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #9: OK
testing release v5.1
testing commit e93c9c99a629c61837d5a7fc2120cd2b6c70dbdd with gcc (GCC) 8.1.0
kernel signature: 90c1653899bae8b13a553522e9e0d4d6adfc32e6506a1d2b8b70c010e9d816c3
run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: OK
testing release v5.0
testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783 with gcc (GCC) 8.1.0
kernel signature: bb29bece72ab00c4b4fa2ecc230d8c4a1be88aa7f95cfcabf4525849e1ae6dac
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.20
testing commit 8fe28cb58bcb235034b64cbbb7550a8a43fd88be with gcc (GCC) 8.1.0
kernel signature: d7505f992a93654ef55078ae45f8f260d7ff60089e2763f1bf7554a5042f40dc
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: basic kernel testing failed: failed to copy test binary to VM: failed to run ["scp" "-P" "22" "-F" "/dev/null" "-o" "UserKnownHostsFile=/dev/null" "-o" "BatchMode=yes" "-o" "IdentitiesOnly=yes" "-o" "StrictHostKeyChecking=no" "-o" "ConnectTimeout=10" "-i" "/syzkaller/jobs/linux/workdir/image/key" "/tmp/syz-executor560042035" "root@10.128.0.218:./syz-executor560042035"]: exit status 1
Connection timed out during banner exchange
lost connection

testing release v4.19
testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d with gcc (GCC) 8.1.0
kernel signature: a9ff4a0e1a4f37bdfe59c8a8ac845334c9b57fde9bf031393a960b6067d9a7f6
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #9: boot failed: can't ssh into the instance
testing release v4.18
testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 with gcc (GCC) 8.1.0
kernel signature: c447df212292d107a979e43e5b0aa0423dd857d70e781d7f448080f49ebd027b
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.17
testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0
kernel signature: 75b4356160c9375a97193ed2e186e68791da406b3205aba446a905eecd983720
run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #2: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #6: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #7: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #8: OK
run #9: OK
testing release v4.16
testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0
kernel signature: d89a3c02ed61ca587242524c6cf80e5c10a2ac81d6b475e78b4739c8ea19237f
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #4: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #9: crashed: KASAN: use-after-free Write in ex_handler_refcount
testing release v4.15
testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0
kernel signature: 6e2c74b25bed7772b2cb8b52188a46a8b8cba3e152a4d46c26a76f51a349ca5a
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #4: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #5: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: kernel BUG at ADDR [verbose debug info unavailable]
testing release v4.14
testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 with gcc (GCC) 8.1.0
kernel signature: 078866dbf44f650476ad8fd91982b570ef3d19ca3bcb7c6de67ac80516a68f9c
all runs: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.13
testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 with gcc (GCC) 8.1.0
kernel signature: 285ddac7e579d5e43cfec8dbbcf8c804b1d6ba29a9f9fae0ba299df67744de71
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: INFO: task hung in synchronize_rcu
testing release v4.12
testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c with gcc (GCC) 8.1.0
kernel signature: 838724e8fe973cb2aff6c3d6d63a86b185f6c98be0bf1a65f013171aa50f9264
all runs: crashed: BUG: sleeping function called from invalid context in tap_get_minor
testing release v4.11
testing commit a351e9b9fc24e982ec2f0e76379a49826036da12 with gcc (GCC) 7.3.0
kernel signature: 0b3433c68f56db865d4e240d999519470905723b3020d23fb30dcdc4ede3eb5e
all runs: crashed: BUG: sleeping function called from invalid context in tap_get_minor
testing release v4.10
testing commit c470abd4fde40ea6a0846a2beab642a578c0b8cd with gcc (GCC) 5.5.0
kernel signature: f22328c37077b3182ee2819e9befb0d45f6b178d3e678fc97901aa59afb1d9e4
all runs: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.9
testing commit 69973b830859bc6529a7a0468ba0d80ee5117826 with gcc (GCC) 5.5.0
kernel signature: 52e700451d4bfe9c2096b01a1ce271ca5d4b3dc44f65e3760e5cdb941169a492
all runs: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.8
testing commit c8d2bc9bc39ebea8437fd974fdbc21847bb897a3 with gcc (GCC) 5.5.0
kernel signature: ffa329fdce1532e78b1a8a27e3361bb11847115dcf2a8cf55ca8ab246782060d
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: INFO: task hung in synchronize_rcu
run #9: boot failed: can't ssh into the instance
testing release v4.7
testing commit 523d939ef98fd712632d93a5a2b588e477a7565e with gcc (GCC) 5.5.0
kernel signature: ce3d58116644d037a9eebc74bf45da0d70248c0452993e1fafc214d5ca3c9bac
run #0: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #1: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #2: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #4: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #7: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: boot failed: WARNING: KASAN doesn't support memory hot-add
testing release v4.6
testing commit 2dcd0af568b0cf583645c8a317dd12e344b1c72a with gcc (GCC) 5.5.0
kernel signature: b0a6eecc8a5051f66e7ea40278556ccd89509dac73e8d395fd47e95b8ed6b87f
run #0: crashed: WARNING in sysfs_warn_dup
run #1: crashed: WARNING in sysfs_warn_dup
run #2: crashed: WARNING in sysfs_warn_dup
run #3: crashed: WARNING in sysfs_warn_dup
run #4: crashed: WARNING in sysfs_warn_dup
run #5: crashed: WARNING in sysfs_warn_dup
run #6: crashed: WARNING in sysfs_warn_dup
run #7: crashed: WARNING in sysfs_warn_dup
run #8: boot failed: WARNING: KASAN doesn't support memory hot-add
run #9: boot failed: WARNING: KASAN doesn't support memory hot-add
revisions tested: 22, total time: 4h42m38.491305708s (build: 2h4m54.019701596s, test: 2h34m43.24150365s)
the crash already happened on the oldest tested release
commit msg: Linux 4.6
crash: WARNING in sysfs_warn_dup
IPv6: ADDRCONF(NETDEV_UP): bridge_slave_1: link is not ready
bond0: Enslaving bond_slave_0 as an active interface with an up link
bond0: Enslaving bond_slave_1 as an active interface with an up link
IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
------------[ cut here ]------------
WARNING: CPU: 1 PID: 6973 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x7b/0xa0 fs/sysfs/dir.c:30
sysfs: cannot create duplicate filename '/class/macvtap/tap50'
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 6973 Comm: syz-executor.5 Not tainted 4.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 1ffffffff0d95756 ffff8800b50aefb0 ffffffff82c74fc6 ffffffff85c81040
 ffff8800b50af088 ffffffff85d2bac0 ffffffff81922ccb ffff8800b50af078
 ffffffff8160cf4e 0000000041b58ab3 ffffffff868f2161 ffffffff8160cd9f
Call Trace:
 [<ffffffff82c74fc6>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff82c74fc6>] dump_stack+0xe6/0x120 lib/dump_stack.c:51
 [<ffffffff8160cf4e>] panic+0x1af/0x348 kernel/panic.c:152
 [<ffffffff8133960d>] __warn+0x18d/0x1b0 kernel/panic.c:504
 [<ffffffff813396c2>] warn_slowpath_fmt+0x92/0xb0 kernel/panic.c:527
 [<ffffffff81922ccb>] sysfs_warn_dup+0x7b/0xa0 fs/sysfs/dir.c:30
 [<ffffffff81923561>] sysfs_do_create_link_sd.isra.2+0xd1/0xf0 fs/sysfs/symlink.c:51
 [<ffffffff819235c3>] sysfs_do_create_link fs/sysfs/symlink.c:80 [inline]
 [<ffffffff819235c3>] sysfs_create_link+0x43/0xb0 fs/sysfs/symlink.c:92
 [<ffffffff83547c79>] device_add_class_symlinks drivers/base/core.c:891 [inline]
 [<ffffffff83547c79>] device_add+0x689/0x1360 drivers/base/core.c:1086
 [<ffffffff83548cb8>] device_create_groups_vargs+0x1c8/0x220 drivers/base/core.c:1709
 [<ffffffff83548db8>] device_create_vargs drivers/base/core.c:1749 [inline]
 [<ffffffff83548db8>] device_create+0x88/0xa0 drivers/base/core.c:1785
 [<ffffffff838e7554>] macvtap_device_event+0x1c4/0x2a0 drivers/net/macvtap.c:1298
 [<ffffffff8139f90b>] notifier_call_chain+0x8b/0x170 kernel/notifier.c:93
 [<ffffffff8139fa11>] __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 [<ffffffff8139fa11>] raw_notifier_call_chain+0x11/0x20 kernel/notifier.c:401
 [<ffffffff84942177>] call_netdevice_notifiers_info+0x47/0x80 net/core/dev.c:1643
 [<ffffffff84967eca>] call_netdevice_notifiers net/core/dev.c:1659 [inline]
 [<ffffffff84967eca>] register_netdevice+0x88a/0xce0 net/core/dev.c:7027
 [<ffffffff838e02a9>] macvlan_common_newlink+0x8b9/0x1090 drivers/net/macvlan.c:1316
 [<ffffffff838e610f>] macvtap_newlink+0xbf/0x110 drivers/net/macvtap.c:471
 [<ffffffff8499522b>] rtnl_newlink+0xd4b/0x1230 net/core/rtnetlink.c:2466
 [<ffffffff849905d2>] rtnetlink_rcv_msg+0x222/0x680 net/core/rtnetlink.c:3513
 [<ffffffff84b1a1b2>] netlink_rcv_skb+0x242/0x350 net/netlink/af_netlink.c:2277
 [<ffffffff849903a5>] rtnetlink_rcv+0x25/0x30 net/core/rtnetlink.c:3519
 [<ffffffff84b18db5>] netlink_unicast_kernel net/netlink/af_netlink.c:1214 [inline]
 [<ffffffff84b18db5>] netlink_unicast+0x455/0x660 net/netlink/af_netlink.c:1240
 [<ffffffff84b19853>] netlink_sendmsg+0x893/0xb40 net/netlink/af_netlink.c:1786
 [<ffffffff848f20f5>] sock_sendmsg_nosec net/socket.c:612 [inline]
 [<ffffffff848f20f5>] sock_sendmsg+0xb5/0xf0 net/socket.c:622
 [<ffffffff848f30c9>] SYSC_sendto+0x1c9/0x300 net/socket.c:1648
 [<ffffffff848f53b9>] SyS_sendto+0x9/0x10 net/socket.c:1616
 [<ffffffff85b9bf00>] entry_SYSCALL_64_fastpath+0x23/0xc1
Kernel Offset: disabled