bisecting cause commit starting from bee46b309a13ca158c99c325d0408fb2f0db207f
building syzkaller on 2c36e7a75f8689b3da20e1a81a2ee5391f3af6e5
testing commit bee46b309a13ca158c99c325d0408fb2f0db207f with gcc (GCC) 8.1.0
kernel signature: ebcbb093909d086a04de00f1f9d0420415e2b430f2dd555f2b4973ad4cd41f11
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: WARNING: refcount bug in l2cap_chan_put
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: WARNING: refcount bug in l2cap_chan_put
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 Read in l2cap_chan_close
testing release v5.5
testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 with gcc (GCC) 8.1.0
kernel signature: 512d1084da9ac72d733d20c20fc5abaf7c95d2911297402ae74df38a9e70190c
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: 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 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: 97dbccac5c1a604630f92888878d018cde8b855a71eef4a5cb8b9a55a9bdd8a3
all runs: 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: f8a682f64dabc17ee9eae197872a3cc1b06d345633fd7007c3100ed2838aae31
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 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: OK
testing release v5.2
testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 with gcc (GCC) 8.1.0
kernel signature: cf7349f6303e5364bc385558daf4aff70424273e967ec4041339bed41b5285e2
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 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 Write in ex_handler_refcount
run #8: crashed: KASAN: use-after-free Write in ex_handler_refcount
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: 53d3278ec1995ef401d57478a85115b77b1c538c5c8ccd6b47803c2abe038206
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 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: OK
testing release v5.0
testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783 with gcc (GCC) 8.1.0
kernel signature: 1fb912fd0a33af99f080fe082a1d950dd301f7efcc8f6a517abe33028d6d9230
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 Write in ex_handler_refcount
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: 30f6cfbe19330ac589e306d31cb37595b82d7fafca0034989be47a4a0f68b040
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 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: 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: a25f1f7c0ed0d10bd4f3e685980f537964ecb9b5c2e7f8f5b22f8ed09037be83
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 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: OK
testing release v4.18
testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 with gcc (GCC) 8.1.0
kernel signature: c95d8b0c5db3bdc8c2832de9e85e4b544e4c6897a65ca07b586865f0d29124e3
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 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: KASAN: use-after-free Write in ex_handler_refcount
testing release v4.17
testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0
kernel signature: bfff2ca8ae51e2de42c29709d864802897e75c9363d6dad938b0b66d974b0742
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 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 v4.16
testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0
kernel signature: 1db0cf9fe4270cf04e27e5c60340d3e9faa13385fd9df61f9216bfee0a553b01
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 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 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 v4.15
testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0
kernel signature: 048712e5d0c63ecbfecb5aa83280912de889135b0bd22dd8885ea8e1a7d29367
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: 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: kernel BUG at ADDR [verbose debug info unavailable]
run #6: crashed: kernel BUG at ADDR [verbose debug info unavailable]
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 v4.14
testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 with gcc (GCC) 8.1.0
kernel signature: a78d552ca0d0b8b94654d869fd40ca23c943e752151cda3025cd99c9e5bafd52
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 v4.13
testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 with gcc (GCC) 8.1.0
kernel signature: 202c003ecb9e1b4556cd2ba0d4c47a275cc9a6d2323100387302430724771687
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: e63bcbcf65ddd8adb3a6eb524ecc5fcd593b47e11555d6d951fd38c62ca3ccfb
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: 0f2c81c403f431f24bb4a2408746c1e2137d0fbd5d61587040b35eb66c7e176e
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: c439e4623640fa4d94c8e4d947d03010c2f65c9895d07278f16d4e91612b4526
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: c69dbbfe357f9d0e4158c0b4a1c6988a9e44e7a471852b93af47e55d295c9b0c
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: b0a5370ae6197ffbdd71db385ba9a376ac02b856446509a78c016b00b4a3706e
all runs: crashed: KASAN: use-after-free Read in l2cap_chan_close
testing release v4.7
testing commit 523d939ef98fd712632d93a5a2b588e477a7565e with gcc (GCC) 5.5.0
kernel signature: 95fd090d80820eeadedc78b4681911d7bb736c79928c52b619abdc453a1da850
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: crashed: INFO: task hung in synchronize_rcu
testing release v4.6
testing commit 2dcd0af568b0cf583645c8a317dd12e344b1c72a with gcc (GCC) 5.5.0
kernel signature: 9f1ed92103df65fac5736cb1cef08970391bcfd36169ac7c514ff41d4b2e0a71
all runs: crashed: WARNING in sysfs_warn_dup
revisions tested: 22, total time: 3h57m37.026575148s (build: 1h56m32.410240542s, test: 1h58m39.580790102s)
the crash already happened on the oldest tested release
commit msg: Linux 4.6
crash: WARNING in sysfs_warn_dup
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): bridge_slave_0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): bridge_slave_1: link is not ready
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7522 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: 7522 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 ffff8800b6baefb0 ffffffff82c74fc6 ffffffff85c81040
 ffff8800b6baf088 ffffffff85d2bac0 ffffffff81922ccb ffff8800b6baf078
 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