bisecting cause commit starting from 5631c5e0eb9035d92ceb20fcd9cdb7779a3f5cc7
building syzkaller on ff51e5229e0ee846d2fd687cb0dbca13de758c66
testing commit 5631c5e0eb9035d92ceb20fcd9cdb7779a3f5cc7 with gcc (GCC) 8.1.0
kernel signature: 6fae5251b3011612598db052cee886ddc28a83d6c7f12ccbad7ad27525dccda9
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
testing release v5.8
testing commit bcf876870b95592b52519ed4aafcf9d95999bc9c with gcc (GCC) 8.1.0
kernel signature: 8de8b6c5d4905ef9758403e50474f0c6d700b63fe6978b14bfd3812cf2ce23fd
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
testing release v5.7
testing commit 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162 with gcc (GCC) 8.1.0
kernel signature: ec94482409b074dccb57cada1afbd15f17481bccb34831f18aed0e0c021acf5c
all runs: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
testing release v5.6
testing commit 7111951b8d4973bda27ff663f2cf18b663d15b48 with gcc (GCC) 8.1.0
kernel signature: 8c8719581c384fe73ed563d573d466a34334f16f6488ee98293edf3af2cd41a6
all runs: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
testing release v5.5
testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 with gcc (GCC) 8.1.0
kernel signature: 2a2cec5e7fca2f4848a13926812e7b767696901e55d5109eedf7917d35dd8148
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #2: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #3: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #4: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #5: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #6: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #7: crashed: KASAN: null-ptr-deref Write in l2cap_chan_put
run #8: crashed: KASAN: use-after-free Read in lock_sock_nested
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v5.4
testing commit 219d54332a09e8d8741c1e1982f5eae56099de85 with gcc (GCC) 8.1.0
kernel signature: a2ede96792c7cc53a72b2d65a91f054730407db70605b57df811ec599bd2a873
run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #1: crashed: KASAN: use-after-free Read in lock_sock_nested
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #6: crashed: KASAN: use-after-free Read in lock_sock_nested
run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v5.3
testing commit 4d856f72c10ecb060868ed10ff1b1453943fc6c8 with gcc (GCC) 8.1.0
kernel signature: c163c44953c18769142442a0677ebe6bb5c5592e748879909871088f8aaeaa4f
run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #5: crashed: KASAN: use-after-free Read in lock_sock_nested
run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v5.2
testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 with gcc (GCC) 8.1.0
kernel signature: ddd33cbc3ae1d9262a1f68937f7419ddf60d38c0e47473117586b005ddea2dc7
run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #6: crashed: KASAN: use-after-free Read in lock_sock_nested
run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v5.1
testing commit e93c9c99a629c61837d5a7fc2120cd2b6c70dbdd with gcc (GCC) 8.1.0
kernel signature: 1f0e0f3734b3bce318a81928cc2bcbc630433d4a5fdaa2fa13b41f2ace01649d
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: KASAN: use-after-free Read in lock_sock_nested
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #7: crashed: KASAN: use-after-free Read in lock_sock_nested
run #8: crashed: KASAN: use-after-free Read in lock_sock_nested
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v5.0
testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783 with gcc (GCC) 8.1.0
kernel signature: 21ff7d01a70b502ccb221f00eab2a3eed97cf05f6e367194aee02fbfaa6b927d
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #4: crashed: KASAN: use-after-free Read in lock_sock_nested
run #5: crashed: KASAN: use-after-free Read in lock_sock_nested
run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #7: crashed: KASAN: use-after-free Read in lock_sock_nested
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.20
testing commit 8fe28cb58bcb235034b64cbbb7550a8a43fd88be with gcc (GCC) 8.1.0
kernel signature: a12c8930b87c4f5f1440938d3459feb7ff9f28b6a1dcef6816b396688686f84f
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #2: crashed: KASAN: use-after-free Read in lock_sock_nested
run #3: crashed: KASAN: use-after-free Read in lock_sock_nested
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #5: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #7: crashed: INFO: trying to register non-static key in l2cap_chan_close
run #8: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #9: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
testing release v4.19
testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d with gcc (GCC) 8.1.0
kernel signature: 22fd0aecff658ad9d0d735d97c32e6c2b905b943fbdfe17a800348f6aa564bb4
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #2: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #3: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #4: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #5: crashed: KASAN: use-after-free Read in lock_sock_nested
run #6: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #7: crashed: BUG: unable to handle kernel NULL pointer dereference in l2cap_chan_put
run #8: crashed: KASAN: use-after-free Read in lock_sock_nested
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.18
testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 with gcc (GCC) 8.1.0
kernel signature: cf42beea014a6ea884b57fc60ecc7658063472f5dc022a06c5bfa82f2ce81231
all runs: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.17
testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0
kernel signature: 1498dd07442312cedef0cd5be7af332fce12dece0aaadf5b4b9d70a32dfe17e9
run #0: crashed: KASAN: use-after-free Read in lock_sock_nested
run #1: crashed: KASAN: use-after-free Read in lock_sock_nested
run #2: crashed: INFO: trying to register non-static key in l2cap_chan_close
run #3: crashed: KASAN: use-after-free Read in lock_sock_nested
run #4: crashed: KASAN: use-after-free Read in lock_sock_nested
run #5: crashed: KASAN: use-after-free Read in lock_sock_nested
run #6: crashed: KASAN: use-after-free Read in lock_sock_nested
run #7: crashed: KASAN: use-after-free Read in lock_sock_nested
run #8: crashed: KASAN: use-after-free Read in lock_sock_nested
run #9: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.16
testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0
kernel signature: df9f527024f7125b3e276046e38d6c35f67a85203c045f6b944b020faf18500e
all runs: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.15
testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0
kernel signature: a78ca4633405f505ac61bb466f3cc04ca0be7c2c2448a0b0efca205c33edf24f
all runs: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.14
testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 with gcc (GCC) 8.1.0
kernel signature: 6a37c7b0bb2fa62ca54bb061342990644deba18bf5d233044fa230064ce8a762
all runs: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.13
testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 with gcc (GCC) 8.1.0
kernel signature: 1cfded2922cf46b0d7c5826cfc4a0d024817873f30e0f6a2daad2c2ba47aee32
all runs: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.12
testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c with gcc (GCC) 8.1.0
kernel signature: bbaec4f581d2de2d6908b0cf72993a1e555b8d81c3dae99ddd9572175df63b50
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: 60cb297c3f308ca806fc9ea4299063ef201c657858f34013a4e0a3693dea9c74
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: a9d3345592d9c73a08c1fbe0da9e33c4796bf47dad6cda6da6d3e959b1f76976
all runs: crashed: KASAN: use-after-free Read in lock_sock_nested
testing release v4.9
testing commit 69973b830859bc6529a7a0468ba0d80ee5117826 with gcc (GCC) 5.5.0
kernel signature: dfe218ac6fe149a5cfd56df72b18ffc61e7bd41d6ed4e47595e1ec77c79b1ffd
run #0: crashed: WARNING in nf_unregister_net_hook
run #1: crashed: WARNING in nf_unregister_net_hook
run #2: crashed: KASAN: use-after-free Write in lockref_get_not_dead
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: 0e6e12e689a16f5ff7e3982c3e1a1312ce7350ed2328dc8fd6884ae96a63816a
run #0: crashed: KASAN: use-after-free Read in vlan_device_event
run #1: OK
run #2: OK
run #3: OK
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
testing release v4.7
testing commit 523d939ef98fd712632d93a5a2b588e477a7565e with gcc (GCC) 5.5.0
kernel signature: 606269d8bae48eda99431743f6586a1a3f3b8880c4fe0bcb492cf58e736c2f4f
run #0: crashed: KASAN: use-after-free Read in lockref_get_not_dead
run #1: OK
run #2: OK
run #3: OK
run #4: OK
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: f816b1e5aaa71300c5b138b82f7b9cebdb3d35e11ddb657d07a0c79c03928119
all runs: crashed: WARNING in sysfs_warn_dup
revisions tested: 25, total time: 4h27m50.701141655s (build: 2h10m52.382545942s, test: 2h13m10.315538512s)
the crash already happened on the oldest tested release
commit msg: Linux 4.6
crash: WARNING in sysfs_warn_dup
IPv6: ADDRCONF(NETDEV_UP): hsr_slave_1: link is not ready
bridge0: port 2(bridge_slave_1) entered blocking state
bridge0: port 2(bridge_slave_1) entered disabled state
device bridge_slave_1 entered promiscuous mode
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5876 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: 5876 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
 0000000000000000 ffff8800b9e5efc8 ffffffff82c65e52 ffffffff85c81040
 ffff8800b9e5f0a0 ffffffff85d2bb80 ffffffff8191bd7b 0000000000000009
 ffff8800b9e5f090 ffffffff8160d884 0000000041b58ab3 ffffffff868f8c5a
Call Trace:
 [<ffffffff82c65e52>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff82c65e52>] dump_stack+0x136/0x1d4 lib/dump_stack.c:51
 [<ffffffff8160d884>] panic+0x1af/0x348 kernel/panic.c:152
 [<ffffffff81335ecd>] __warn+0x18d/0x1b0 kernel/panic.c:504
 [<ffffffff81335f82>] warn_slowpath_fmt+0x92/0xb0 kernel/panic.c:527
 [<ffffffff8191bd7b>] sysfs_warn_dup+0x7b/0xa0 fs/sysfs/dir.c:30
 [<ffffffff8191c5f1>] sysfs_do_create_link_sd.isra.0+0xd1/0xf0 fs/sysfs/symlink.c:51
 [<ffffffff8191c653>] sysfs_do_create_link fs/sysfs/symlink.c:80 [inline]
 [<ffffffff8191c653>] sysfs_create_link+0x43/0xb0 fs/sysfs/symlink.c:92
 [<ffffffff83531337>] device_add_class_symlinks drivers/base/core.c:891 [inline]
 [<ffffffff83531337>] device_add+0x677/0x1350 drivers/base/core.c:1086
 [<ffffffff83532378>] device_create_groups_vargs+0x1c8/0x220 drivers/base/core.c:1709
 [<ffffffff83532478>] device_create_vargs drivers/base/core.c:1749 [inline]
 [<ffffffff83532478>] device_create+0x88/0xa0 drivers/base/core.c:1785
 [<ffffffff838d1764>] macvtap_device_event+0x1c4/0x2a0 drivers/net/macvtap.c:1298
 [<ffffffff81399feb>] notifier_call_chain+0x8b/0x170 kernel/notifier.c:93
 [<ffffffff8139a0f1>] __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 [<ffffffff8139a0f1>] raw_notifier_call_chain+0x11/0x20 kernel/notifier.c:401
 [<ffffffff84946047>] call_netdevice_notifiers_info+0x47/0x80 net/core/dev.c:1643
 [<ffffffff8496aa98>] call_netdevice_notifiers net/core/dev.c:1659 [inline]
 [<ffffffff8496aa98>] register_netdevice+0x8e8/0xd00 net/core/dev.c:7027
 [<ffffffff838c8eb9>] macvlan_common_newlink+0x8b9/0x1090 drivers/net/macvlan.c:1316
 [<ffffffff838cfb2f>] macvtap_newlink+0xbf/0x110 drivers/net/macvtap.c:471
 [<ffffffff8499b54b>] rtnl_newlink+0xd4b/0x1230 net/core/rtnetlink.c:2466
 [<ffffffff84995ff2>] rtnetlink_rcv_msg+0x222/0x680 net/core/rtnetlink.c:3513
 [<ffffffff84b19612>] netlink_rcv_skb+0x242/0x350 net/netlink/af_netlink.c:2277
 [<ffffffff84995dc5>] rtnetlink_rcv+0x25/0x30 net/core/rtnetlink.c:3519
 [<ffffffff84b181aa>] netlink_unicast_kernel net/netlink/af_netlink.c:1214 [inline]
 [<ffffffff84b181aa>] netlink_unicast+0x3da/0x560 net/netlink/af_netlink.c:1240
 [<ffffffff84b18ddb>] netlink_sendmsg+0x9bb/0xb40 net/netlink/af_netlink.c:1786
 [<ffffffff848f52d5>] sock_sendmsg_nosec net/socket.c:612 [inline]
 [<ffffffff848f52d5>] sock_sendmsg+0xb5/0xf0 net/socket.c:622
 [<ffffffff848f90ca>] SYSC_sendto net/socket.c:1648 [inline]
 [<ffffffff848f90ca>] SyS_sendto+0x1ca/0x290 net/socket.c:1616
 [<ffffffff85b96100>] entry_SYSCALL_64_fastpath+0x23/0xc1
Kernel Offset: disabled