bisecting cause commit starting from a69e90512d9def6bd8064d84cff9ffd8b15eaa1b building syzkaller on 8fd428a197f1ff27bdb6d3d359745e2756133d01 testing commit a69e90512d9def6bd8064d84cff9ffd8b15eaa1b with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v5.2 testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v5.1 testing commit e93c9c99a629c61837d5a7fc2120cd2b6c70dbdd with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v5.0 testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783 with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v4.20 testing commit 8fe28cb58bcb235034b64cbbb7550a8a43fd88be with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v4.19 testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v4.18 testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v4.17 testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v4.16 testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0 all runs: crashed: WARNING: refcount bug in cdev_get testing release v4.15 testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0 run #0: crashed: WARNING: refcount bug in cdev_get run #1: crashed: WARNING: refcount bug in cdev_get run #2: crashed: WARNING: refcount bug in cdev_get run #3: crashed: WARNING: refcount bug in cdev_get run #4: crashed: WARNING: refcount bug in cdev_get run #5: crashed: WARNING: refcount bug in cdev_get run #6: crashed: WARNING: refcount bug in cdev_get run #7: crashed: WARNING: refcount bug in cdev_get run #8: OK run #9: OK testing release v4.14 testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 with gcc (GCC) 8.1.0 run #0: crashed: WARNING: refcount bug in cdev_get run #1: crashed: WARNING: refcount bug in cdev_get run #2: crashed: WARNING: refcount bug in cdev_get run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing release v4.13 testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 with gcc (GCC) 8.1.0 run #0: crashed: WARNING: refcount bug in cdev_get run #1: crashed: WARNING: refcount bug in cdev_get run #2: crashed: WARNING: refcount bug in cdev_get run #3: crashed: WARNING: refcount bug in cdev_get run #4: crashed: WARNING: refcount bug in cdev_get run #5: crashed: WARNING: refcount bug in cdev_get run #6: OK run #7: OK run #8: OK run #9: OK testing release v4.12 testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c with gcc (GCC) 8.1.0 run #0: crashed: WARNING: refcount bug in cdev_get run #1: crashed: WARNING: refcount bug in cdev_get run #2: crashed: WARNING: refcount bug in cdev_get run #3: crashed: WARNING: refcount bug in cdev_get run #4: crashed: WARNING: refcount bug in cdev_get run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing release v4.11 testing commit a351e9b9fc24e982ec2f0e76379a49826036da12 with gcc (GCC) 7.3.0 run #0: crashed: WARNING: refcount bug in cdev_get run #1: crashed: WARNING: refcount bug in cdev_get run #2: crashed: WARNING: refcount bug in cdev_get run #3: crashed: WARNING: refcount bug in cdev_get run #4: crashed: WARNING: refcount bug in cdev_get run #5: crashed: WARNING: refcount bug in cdev_get run #6: OK run #7: OK run #8: OK run #9: OK testing release v4.10 testing commit c470abd4fde40ea6a0846a2beab642a578c0b8cd with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get run #4: crashed: WARNING in kobject_get run #5: crashed: WARNING in kobject_get run #6: crashed: WARNING in kobject_get run #7: OK run #8: OK run #9: OK testing release v4.9 testing commit 69973b830859bc6529a7a0468ba0d80ee5117826 with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get run #4: crashed: WARNING in kobject_get run #5: crashed: WARNING in kobject_get 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 run #0: crashed: WARNING in kobject_get 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 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get 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 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get run #4: crashed: WARNING in kobject_get run #5: OK run #6: crashed: WARNING in kobject_get run #7: OK run #8: OK run #9: OK testing release v4.5 testing commit b562e44f507e863c6792946e4e1b1449fbbac85d with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get run #4: crashed: WARNING in kobject_get run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing release v4.4 testing commit afd2ff9b7e1b367172f18ba7f693dfb62bdcb2dc with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get run #4: crashed: WARNING in kobject_get run #5: crashed: WARNING in kobject_get run #6: crashed: WARNING in kobject_get run #7: OK run #8: OK run #9: OK testing release v4.3 testing commit 6a13feb9c82803e2b815eca72fa7a9f5561d7861 with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: no output from test machine run #2: crashed: no output from test machine run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing release v4.2 testing commit 64291f7db5bd8150a74ad2036f1037e6a0428df2 with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: WARNING in kobject_get run #4: crashed: WARNING in kobject_get run #5: crashed: no output from test machine run #6: crashed: WARNING in kobject_get run #7: 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-executor967503288" "root@10.128.0.15:./syz-executor967503288"]: exit status 1 ssh: connect to host 10.128.0.15 port 22: Connection timed out lost connection run #8: 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-executor425387946" "root@10.128.1.40:./syz-executor425387946"]: exit status 1 ssh: connect to host 10.128.1.40 port 22: Connection timed out lost connection run #9: OK testing release v4.1 testing commit b953c0d234bc72e8489d3bf51a276c5c4ec85345 with gcc (GCC) 5.5.0 run #0: crashed: WARNING in kobject_get run #1: crashed: WARNING in kobject_get run #2: crashed: WARNING in kobject_get run #3: crashed: no output from test machine run #4: crashed: WARNING in kobject_get run #5: crashed: WARNING in kobject_get run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 24, total time: 5h25m27.18384446s (build: 1h48m48.178032833s, test: 3h29m5.978997967s) the crash already happened on the oldest tested release crash: WARNING in kobject_get input: syz1 as /devices/virtual/input/input17144 input: syz1 as /devices/virtual/input/input17145 input: syz1 as /devices/virtual/input/input17146 input: syz1 as /devices/virtual/input/input17148 ------------[ cut here ]------------ WARNING: CPU: 0 PID: 2762 at include/linux/kref.h:47 kref_get include/linux/kref.h:47 [inline]() WARNING: CPU: 0 PID: 2762 at include/linux/kref.h:47 kobject_get+0x7a/0x90 lib/kobject.c:584() Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 2762 Comm: syz-executor.3 Not tainted 4.1.0 #1 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffffffff82e32302 ffff88012b74bad8 ffffffff8263cd0b 0000000000000032 ffffffff82e32413 ffff88012b74bb58 ffffffff82638b9e ffff88012b74baf8 ffffffff00000008 ffff88012b74bb68 ffff88012b74bb08 0000000000000000 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0x4f/0x7b lib/dump_stack.c:50 [] panic+0xcd/0x211 kernel/panic.c:111 [] warn_slowpath_common+0xbb/0xc0 kernel/panic.c:442 [] warn_slowpath_null+0x15/0x20 kernel/panic.c:479 [] kref_get include/linux/kref.h:47 [inline] [] kobject_get+0x7a/0x90 lib/kobject.c:584 [] cdev_get+0x27/0x50 fs/char_dev.c:329 [] chrdev_open+0x3a/0x1c0 fs/char_dev.c:374 [] do_dentry_open+0x227/0x350 fs/open.c:734 [] vfs_open+0x49/0x50 fs/open.c:871 [] do_last+0x257/0x1720 fs/namei.c:3104 [] path_openat+0x7b/0x6a0 fs/namei.c:3243 [] do_filp_open+0x35/0xb0 fs/namei.c:3290 [] do_sys_open+0x126/0x220 fs/open.c:1014 [] SYSC_open fs/open.c:1032 [inline] [] SyS_open+0x19/0x20 fs/open.c:1027 [] system_call_fastpath+0x16/0x7a Kernel Offset: disabled