bisecting fixing commit since 0c88e405c97ed1828443b67891e6d4bb6e56cd4e building syzkaller on e34b696c0d7c04dbc824dee8b5123969bbca19b7 testing commit 0c88e405c97ed1828443b67891e6d4bb6e56cd4e with gcc (GCC) 8.4.1 20210217 kernel signature: 35a0302be55d0e3087b12343b0534438c04f1285bdb95e7a42d9e0cc88321faf run #0: crashed: general protection fault in vgem_fence_attach_ioctl run #1: crashed: general protection fault in vgem_fence_attach_ioctl run #2: crashed: WARNING in mutex_destroy run #3: crashed: general protection fault in vgem_fence_attach_ioctl run #4: crashed: WARNING in mutex_destroy run #5: crashed: general protection fault in vgem_fence_attach_ioctl run #6: crashed: general protection fault in vgem_fence_attach_ioctl run #7: crashed: general protection fault in vgem_fence_attach_ioctl run #8: crashed: general protection fault in vgem_fence_attach_ioctl run #9: crashed: general protection fault in vgem_fence_attach_ioctl run #10: crashed: general protection fault in vgem_fence_attach_ioctl run #11: crashed: WARNING in mutex_destroy run #12: crashed: general protection fault in vgem_fence_attach_ioctl run #13: crashed: general protection fault in vgem_fence_attach_ioctl run #14: crashed: general protection fault in vgem_fence_attach_ioctl run #15: crashed: KASAN: use-after-free Read in reservation_object_test_signaled_rcu run #16: crashed: WARNING in mutex_destroy run #17: crashed: general protection fault in vgem_fence_attach_ioctl run #18: crashed: WARNING in mutex_destroy run #19: crashed: WARNING in mutex_destroy testing current HEAD 6b7b0056defc6eb5c87bbe4690ccda547b2891aa testing commit 6b7b0056defc6eb5c87bbe4690ccda547b2891aa with gcc (GCC) 8.4.1 20210217 kernel signature: 0690cf8f0f204dbc69c05cae0727f8e426d34e1f8c9f60b4d9c4a4dfed396f08 run #0: crashed: general protection fault in vgem_fence_attach_ioctl run #1: crashed: general protection fault in vgem_fence_attach_ioctl run #2: crashed: WARNING in mutex_destroy run #3: crashed: general protection fault in vgem_fence_attach_ioctl run #4: crashed: WARNING in mutex_destroy run #5: crashed: WARNING in mutex_destroy run #6: crashed: WARNING in mutex_destroy run #7: crashed: general protection fault in vgem_fence_attach_ioctl run #8: crashed: WARNING in mutex_destroy run #9: crashed: general protection fault in vgem_fence_attach_ioctl revisions tested: 2, total time: 34m53.383450874s (build: 15m43.220323994s, test: 18m44.353303144s) the crash still happens on HEAD commit msg: Linux 4.19.192 crash: general protection fault in vgem_fence_attach_ioctl bond0 (unregistering): Releasing backup interface bond_slave_1 bond0 (unregistering): Releasing backup interface bond_slave_0 bond0 (unregistering): Released all slaves kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 31976 Comm: syz-executor975 Not tainted 4.19.192-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:vgem_fence_attach_ioctl+0x250/0x580 drivers/gpu/drm/vgem/vgem_fence.c:184 Code: 80 3c 02 00 0f 85 01 03 00 00 4d 8b bc 24 10 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bf e0 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cd 02 00 00 49 8b 87 e0 00 00 00 4c 89 f2 48 c1 RSP: 0018:ffff8881c5f6fa70 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: ffff8881d6eb17c0 RCX: 0000000000000000 RDX: 000000000000001c RSI: 0000000000000001 RDI: 00000000000000e0 RBP: ffff8881c5f6fab0 R08: ffffed103eca4561 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881f4dbc540 R13: ffff8881e6db43c0 R14: ffff8881d6eb17c4 R15: 0000000000000000 FS: 00007fa7660db700(0000) GS:ffff8881f6500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffe75f00ba8 CR3: 00000001f4730005 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: drm_ioctl_kernel+0x1b7/0x240 drivers/gpu/drm/drm_ioctl.c:757 drm_ioctl+0x6a9/0xae0 drivers/gpu/drm/drm_ioctl.c:857 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x44a299 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa7660db308 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004cb508 RCX: 000000000044a299 RDX: 0000000020000140 RSI: 00000000c10c5541 RDI: 0000000000000005 RBP: 00000000004cb500 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cb50c R13: 000000000049b07c R14: 6972642f7665642f R15: 0000000000022000 Modules linked in: ---[ end trace 994fb06871c115fe ]--- RIP: 0010:vgem_fence_attach_ioctl+0x250/0x580 drivers/gpu/drm/vgem/vgem_fence.c:184 Code: 80 3c 02 00 0f 85 01 03 00 00 4d 8b bc 24 10 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bf e0 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cd 02 00 00 49 8b 87 e0 00 00 00 4c 89 f2 48 c1 RSP: 0018:ffff8881c5f6fa70 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: ffff8881d6eb17c0 RCX: 0000000000000000 RDX: 000000000000001c RSI: 0000000000000001 RDI: 00000000000000e0 RBP: ffff8881c5f6fab0 R08: ffffed103eca4561 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881f4dbc540 R13: ffff8881e6db43c0 R14: ffff8881d6eb17c4 R15: 0000000000000000 FS: 00007fa7660db700(0000) GS:ffff8881f6400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004d16e0 CR3: 00000001f4730003 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400