bisecting cause commit starting from 8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b
building syzkaller on 1b201b48c59d619af21de7fcc5face22824c0285
testing commit 8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b
compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: 2db6c0d72d7bfdb45502b7d1fc3f94b9990a457dd420db628c17fb6de8693671
all runs: crashed: WARNING in internal_create_group
testing release v5.13
testing commit 62fb9874f5da54fdb243003b386128037319b219
compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: 909f5b513362d755e99068620c19525cb2afd91ca8725228219fd46574a48866
all runs: crashed: WARNING in nbd_dev_add
testing release v5.12
testing commit 9f4ad9e425a1d3b6a34617b8ea226d56a119a717
compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: bb4e26dd8f4a005b0fd76547575ef29621d4d502b5251ddaf0a5696974104629
all runs: crashed: WARNING in nbd_dev_add
testing release v5.11
testing commit f40ddce88593482919761f74910f42f4b84c004b
compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: 3222e6ed80513dd888ba5df1ed0bb0fed90b38311471a07f8ebfef14f678fd42
all runs: crashed: WARNING in nbd_dev_add
testing release v5.10
testing commit 2c85ebc57b3e1817b6ce1a6b703928e113a90442
compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: 35c88fb67e0626f0232c5254d6e9f188ff33bdc5ecf75a2e20b39b0354577e82
all runs: crashed: WARNING in nbd_dev_add
testing release v5.9
testing commit bbf5c979011a099af5dc76498918ed7df445635b
compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: 4753fc6113ccf19b73886623e431f1d42203e5df7900561c23ce4babeaf8f756
all runs: crashed: WARNING in nbd_dev_add
testing release v5.8
testing commit bcf876870b95592b52519ed4aafcf9d95999bc9c
compiler: gcc (GCC) 8.4.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: 64bef9c619e4f9660afe7c971d6b25d7fe2654ae1e3be1137534ef774e1b1619
all runs: crashed: WARNING in nbd_dev_add
testing release v5.7
testing commit 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162
compiler: gcc version 8.4.1 20210217 (GCC), GNU ld (GNU Binutils for Debian) 2.35.1
kernel signature: f76fe31c01316385978519b5b4e89add706a0c3d5fe63afc28097ce825bd70af
all runs: crashed: WARNING in nbd_dev_add
testing release v5.6
testing commit 7111951b8d4973bda27ff663f2cf18b663d15b48
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: ce1c40f29ea7dac1ab1efcb8a4c28e91d707e6db2dd3c7ba2f4d3ff05339b929
all runs: crashed: WARNING in nbd_dev_add
testing release v5.5
testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 52e3d19b3dd1254ec0fc70d5e850d8b373790b6a1ce2b4832bb7a2a2d3945561
all runs: crashed: WARNING in nbd_dev_add
testing release v5.4
testing commit 219d54332a09e8d8741c1e1982f5eae56099de85
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: aaf25273084462a2ad615141adb1da70de0e843313526173854dc50400e6d06c
all runs: crashed: WARNING in nbd_dev_add
testing release v5.3
testing commit 4d856f72c10ecb060868ed10ff1b1453943fc6c8
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 6a118b86ece6a00ec309dfe958551a7e37b62c5a38c74bfffbdf71d5ff2118cf
all runs: crashed: WARNING in nbd_dev_add
testing release v5.2
testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: dc0a4e06aabc5a71b7bb3c51a117c73e328564b4a4f21cfd43ea9747d8ce137d
all runs: crashed: WARNING in nbd_dev_add
testing release v5.1
testing commit e93c9c99a629c61837d5a7fc2120cd2b6c70dbdd
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 6f28a54ae9631f7a38ae82812fc557e8efc8855fdd74a27360b3ac8c36083bee
all runs: crashed: WARNING in nbd_dev_add
testing release v5.0
testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: cc4af3f53694d3fa6e61b52de0e00edfb6449f3b5e2c0a6ea7e7eb72c3e13ece
all runs: crashed: WARNING in nbd_dev_add
testing release v4.20
testing commit 8fe28cb58bcb235034b64cbbb7550a8a43fd88be
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 0d9004c223341f413ce12d9e5aad0136104ab24c164ce7fb0bcaad52b73da54f
all runs: crashed: WARNING in nbd_dev_add
testing release v4.19
testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 710b4bc111a8da9bbc26f33509f7d947e62d3202e4d33bb1ad31dbcdb094016d
all runs: crashed: WARNING in nbd_dev_add
testing release v4.18
testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: dfbfb2de334264f0a3e1ec1a157454b4bff47a9b88ce459c53506b43373b0efe
all runs: crashed: WARNING in nbd_dev_add
testing release v4.17
testing commit 29dcea88779c856c7dc92040a0c01233263101d4
failed to run ["make" "-j" "64" "ARCH=x86_64" "CC=/syzkaller/shared/bisect_bin/gcc-8.1.0/bin/gcc" "bzImage"]: exit status 2
testing release v4.16
testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda
orc_dump.c:106:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
orc_dump.c:111:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
elf.c:135:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:140:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
testing release v4.15
testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff
orc_dump.c:106:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
orc_dump.c:111:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
elf.c:135:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:140:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
pager.c:36:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
testing release v4.14
testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4
orc_dump.c:105:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
orc_dump.c:110:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
pager.c:36:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
elf.c:134:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:139:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
testing release v4.13
testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261
pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
elf.c:144:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:149:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
testing release v4.12
testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c
pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
elf.c:141:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:146:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
testing release v4.11
testing commit a351e9b9fc24e982ec2f0e76379a49826036da12
elf.c:141:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:146:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
testing release v4.10
testing commit c470abd4fde40ea6a0846a2beab642a578c0b8cd
tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes]
elf.c:129:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:134:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
testing release v4.9
testing commit 69973b830859bc6529a7a0468ba0d80ee5117826
tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes]
elf.c:129:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:134:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
testing release v4.8
testing commit c8d2bc9bc39ebea8437fd974fdbc21847bb897a3
tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes]
elf.c:129:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:134:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
pager.c:33:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
testing release v4.7
testing commit 523d939ef98fd712632d93a5a2b588e477a7565e
tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes]
pager.c:33:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
elf.c:122:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations]
elf.c:127:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations]
testing release v4.6
testing commit 2dcd0af568b0cf583645c8a317dd12e344b1c72a
tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes]
pager.c:33:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict]
revisions tested: 18, total time: 2h59m5.321299131s (build: 1h58m34.968827183s, test: 55m11.994297357s)
the crash already happened on the oldest tested release
commit msg: Linux 4.18
crash: WARNING in nbd_dev_add
RDX: 0000000000000000 RSI: 00000000200002c0 RDI: 0000000000000005
RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffeae48c2af R14: 00007fc31a335300 R15: 0000000000022000
kobject_add_internal failed for 43:0 with -EEXIST, don't try to register things with the same name in the same directory.
WARNING: CPU: 0 PID: 9970 at block/genhd.c:697 __device_add_disk+0xc3c/0xed0 block/genhd.c:709
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 9970 Comm: syz-executor.2 Not tainted 4.18.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x15a/0x20d lib/dump_stack.c:113
 panic+0x1c6/0x36b kernel/panic.c:184
 __warn.cold.7+0x120/0x168 kernel/panic.c:536
 report_bug+0x1a1/0x200 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x200/0x350 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:__device_add_disk+0xc3c/0xed0 block/genhd.c:697
Code: fe 8b 95 30 ff ff ff e9 b9 f4 ff ff 4c 89 ff e8 ea f9 56 fe e9 d6 f4 ff ff e8 60 fa 56 fe e9 3e f7 ff ff 0f 0b e9 3f fc ff ff <0f> 0b e9 c9 fe ff ff 4c 89 e7 e8 45 fa 56 fe e9 de f4 ff ff e8 3b 
RSP: 0018:ffff880089a9f368 EFLAGS: 00010282
RAX: 00000000ffffffef RBX: 1ffff10011353e75 RCX: 1ffff10012ce843f
RDX: dffffc0000000000 RSI: 0000000000000000 RDI: 0000000000000286
RBP: ffff880089a9f470 R08: ffff8800967421f8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800a22eb868
R13: ffff880089a9f448 R14: ffffffff8823a120 R15: ffff8800a22eb300
 device_add_disk+0xe/0x10 block/genhd.c:717
 add_disk include/linux/genhd.h:399 [inline]
 nbd_dev_add+0x652/0x820 drivers/block/nbd.c:1607
 nbd_genl_connect+0x3b9/0x14e0 drivers/block/nbd.c:1699
 genl_family_rcv_msg+0x599/0x1000 net/netlink/genetlink.c:601
 genl_rcv_msg+0xa7/0x140 net/netlink/genetlink.c:626
 netlink_rcv_skb+0x142/0x390 net/netlink/af_netlink.c:2455
 genl_rcv+0x23/0x40 net/netlink/genetlink.c:637
 netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
 netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1343
 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1908
 sock_sendmsg_nosec net/socket.c:642 [inline]
 sock_sendmsg+0xac/0xf0 net/socket.c:652
 ___sys_sendmsg+0x647/0x950 net/socket.c:2126
 __sys_sendmsg+0xd9/0x180 net/socket.c:2164
 __do_sys_sendmsg net/socket.c:2173 [inline]
 __se_sys_sendmsg net/socket.c:2171 [inline]
 __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2171
 do_syscall_64+0xda/0x540 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665e9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48 
RSP: 002b:00007fc31a335188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665e9
RDX: 0000000000000000 RSI: 00000000200002c0 RDI: 0000000000000005
RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffeae48c2af R14: 00007fc31a335300 R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..