bisecting cause commit starting from f8788d86ab28f61f7b46eb6be375f8a726783636
building syzkaller on 59b57593586656c1d5be820aeed0e751087e6ac6
testing commit f8788d86ab28f61f7b46eb6be375f8a726783636 with gcc (GCC) 8.1.0
kernel signature: 3f63c8c22f5cd443e0353189d3c64f7c9ba41d2bbb5233ddb63f0d0f484961c1
run #0: crashed: WARNING: refcount bug in l2cap_chan_put
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: WARNING: refcount bug in l2cap_chan_put
run #5: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #6: crashed: KASAN: use-after-free Write in refcount_warn_saturate
run #7: crashed: WARNING: refcount bug in l2cap_chan_put
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: KASAN: use-after-free Write in refcount_warn_saturate
testing release v5.5
testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 with gcc (GCC) 8.1.0
kernel signature: 637cdeb70bee60300ef058f730e117b482ae8147409077ab9aa51cce241cc0bf
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: WARNING: refcount bug in l2cap_chan_put
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: WARNING: refcount bug in l2cap_chan_put
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: WARNING: refcount bug in l2cap_chan_put
testing release v5.4
testing commit 219d54332a09e8d8741c1e1982f5eae56099de85 with gcc (GCC) 8.1.0
kernel signature: c5b6f9d831d5eec74aca8dbcc24553f5508b99504fd594a37c4caa0e6296c314
run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount
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 Write in ex_handler_refcount
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: 044415e7685fca5f10f24ccc3fafcdba7f55e23edf306dc9c60c07352d08dc59
run #0: crashed: KASAN: use-after-free Write in ex_handler_refcount
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 Write in ex_handler_refcount
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 Write in ex_handler_refcount
run #9: crashed: KASAN: use-after-free Write in ex_handler_refcount
testing release v5.2
testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 with gcc (GCC) 8.1.0
kernel signature: 173ae3e813db349b15754323c0d32958dc34d60386e5e24c3ae2d1e617f2cc8c
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 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: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v5.1
testing commit e93c9c99a629c61837d5a7fc2120cd2b6c70dbdd with gcc (GCC) 8.1.0
kernel signature: 80f078997fd8b70af5d5bf4a23506efafed5eabab7801bd752e9209b026f1111
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 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: crashed: KASAN: use-after-free Write in ex_handler_refcount
run #9: crashed: KASAN: use-after-free Write in ex_handler_refcount
testing release v5.0
testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783 with gcc (GCC) 8.1.0
kernel signature: fa8b0c71281ab4489c792430f6f6f57e4e179ba89806e275c282400b032c2489
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 Read in l2cap_chan_close
run #8: crashed: KASAN: use-after-free Read in l2cap_chan_close
run #9: crashed: KASAN: use-after-free Write in ex_handler_refcount
testing release v4.20
testing commit 8fe28cb58bcb235034b64cbbb7550a8a43fd88be with gcc (GCC) 8.1.0
kernel signature: b747f9cd28c7c27dbd89f0ff8900b6a883a4426e9fc605c314f2f01abf7c7a6b
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 Read in l2cap_chan_close
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 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 v4.19
testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d with gcc (GCC) 8.1.0
kernel signature: 3a54175b4c0b306756fc8fa5c9f0b7ebe17665c71dee934dc276b668f3099972
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 Write in ex_handler_refcount
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: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.18
testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 with gcc (GCC) 8.1.0
kernel signature: 816c00e5e5bf4dfce4345ae68bdfbebbac70316bab6cfdcd0ec43835e5e97859
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 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 Write in ex_handler_refcount
testing release v4.17
testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0
kernel signature: 1d836e6eaf5fdd25fdacf32aa209f85932e2bf392fb7804303b270b5f76935fe
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 Write in ex_handler_refcount
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 v4.16
testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0
kernel signature: 948e48d3026fcd22c62b2a37817b2a1aaebec2cf7d74c8aeb380229df011b377
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 Write in ex_handler_refcount
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 v4.15
testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0
kernel signature: 60c3e5711b73a2aed2f261512f5d9d895d2e987843da3c57ec240605fbd19979
run #0: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #1: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #2: crashed: kernel BUG at ADDR [verbose debug info unavailable]
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: kernel BUG at ADDR [verbose debug info unavailable]
run #7: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #8: crashed: kernel BUG at ADDR [verbose debug info unavailable]
run #9: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.14
testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 with gcc (GCC) 8.1.0
kernel signature: e1e4b88c80438cb077b357b6e48574613015d19f716f4e644358618097e26a91
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: INFO: task hung in synchronize_rcu
run #6: crashed: INFO: task hung in synchronize_rcu
run #7: crashed: INFO: task hung in synchronize_rcu
run #8: crashed: INFO: task hung in synchronize_rcu
run #9: crashed: INFO: task hung in synchronize_rcu
testing release v4.13
testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 with gcc (GCC) 8.1.0
kernel signature: 9eb05fc0cca855de2b4fd0e648c8f86fe29953bf28eaf3dca35778394538151b
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: INFO: task hung in synchronize_rcu
run #6: crashed: INFO: task hung in synchronize_rcu
run #7: crashed: INFO: task hung in synchronize_rcu
run #8: crashed: INFO: task hung in synchronize_rcu
run #9: crashed: INFO: task hung in synchronize_rcu
testing release v4.12
testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c with gcc (GCC) 8.1.0
kernel signature: 16d73fbf344c92336b62af388e3db4a1e39b76346ced4306847eccee0cf4c949
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: 0de9cd42e75b5b4607aa1df85a25b8c30911c6623709a7ba30bb37363078f3f0
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: 8a53bc4d5b24d02d36bdc7fd33f47f14bf5769a94688f10bc79863fade353caf
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 in nf_unregister_net_hook
run #3: crashed: unregister_netdevice: waiting for DEV to become free
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
testing release v4.9
testing commit 69973b830859bc6529a7a0468ba0d80ee5117826 with gcc (GCC) 5.5.0
kernel signature: 5d1280b3e8bb1cba6c6c6747cd1c9dcdf309c471aca9153db5171576dd830cb0
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: OK
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
testing release v4.8
testing commit c8d2bc9bc39ebea8437fd974fdbc21847bb897a3 with gcc (GCC) 5.5.0
kernel signature: 16bc4e76e5ff3ecd9a98eb2bcc72778abe9eca399335bef8d99d4b989aa753f9
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: unregister_netdevice: waiting for DEV to become free
run #8: OK
run #9: OK
testing release v4.7
testing commit 523d939ef98fd712632d93a5a2b588e477a7565e with gcc (GCC) 5.5.0
kernel signature: f28d0af1dbd4c3e30cbea1ef59c018072d367190249ebbdd88ec81b864197cb1
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: unregister_netdevice: waiting for DEV to become free
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
testing release v4.6
testing commit 2dcd0af568b0cf583645c8a317dd12e344b1c72a with gcc (GCC) 5.5.0
kernel signature: ba2a77382fee9890c34c46af80f299df5b2e8f4fbe525308e66207938bd40a1e
all runs: crashed: WARNING in sysfs_warn_dup
revisions tested: 22, total time: 3h56m47.034583445s (build: 1h56m24.70879759s, test: 1h58m12.74141032s)
the crash already happened on the oldest tested release
commit msg: Linux 4.6
crash: WARNING in sysfs_warn_dup
IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
bridge0: port 1(bridge_slave_0) entered blocking state
bridge0: port 1(bridge_slave_0) entered disabled state
device bridge_slave_0 entered promiscuous mode
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7682 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: 0 PID: 7682 Comm: syz-executor.0 Not tainted 4.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 1ffffffff0d95756 ffff8800b9e1ee00 ffffffff82c74fc6 ffffffff85c81040
 ffff8800b9e1eed8 ffffffff85d2bac0 ffffffff81922ccb ffff8800b9e1eec8
 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
 [<ffffffff849ddd72>] C_SYSC_socketcall net/compat.c:810 [inline]
 [<ffffffff849ddd72>] compat_SyS_socketcall+0x482/0x7d0 net/compat.c:768
 [<ffffffff810084e4>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff810084e4>] do_fast_syscall_32+0x324/0xa70 arch/x86/entry/common.c:454
 [<ffffffff85b9e4f4>] entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:125
Kernel Offset: disabled