bisecting fixing commit since dda0e2920330128e0dbdeb11c8f25031aa40b11c building syzkaller on a8c6a3f8da30ccf825c6001c81a8adff21829c30 testing commit dda0e2920330128e0dbdeb11c8f25031aa40b11c with gcc (GCC) 8.1.0 kernel signature: 05880ac0e1715d99bf88ad108765be479b3c2e08f788e211db91e21bd955511c run #0: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create 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 current HEAD 84920cc7fbe10e838689e8e1437dfd18d6e54a2c testing commit 84920cc7fbe10e838689e8e1437dfd18d6e54a2c with gcc (GCC) 8.1.0 kernel signature: eaf39ebd52ab1cdafb3e21c989f0b2fafbc7baa5ac63324c837ccffaa690a5bb run #0: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #1: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #9: OK revisions tested: 2, total time: 44m3.73357229s (build: 20m25.276478549s, test: 21m52.08087814s) the crash still happens on HEAD commit msg: Linux 4.19.121 crash: KASAN: use-after-free Read in vgem_gem_dumb_create bond0 (unregistering): Releasing backup interface bond_slave_1 bond0 (unregistering): Releasing backup interface bond_slave_0 bond0 (unregistering): Released all slaves ================================================================== BUG: KASAN: use-after-free in vgem_gem_dumb_create+0x1d2/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:214 Read of size 8 at addr ffff88808b8e3e00 by task syz-executor013/8902 CPU: 0 PID: 8902 Comm: syz-executor013 Not tainted 4.19.121-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+0x123/0x177 lib/dump_stack.c:118 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 vgem_gem_dumb_create+0x1d2/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:214 drm_mode_create_dumb+0x1ea/0x2b0 drivers/gpu/drm/drm_dumb_buffers.c:92 drm_mode_create_dumb_ioctl+0x9/0x10 drivers/gpu/drm/drm_dumb_buffers.c:98 drm_ioctl_kernel+0x1ab/0x240 drivers/gpu/drm/drm_ioctl.c:752 drm_ioctl+0x47f/0xa00 drivers/gpu/drm/drm_ioctl.c:852 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: 0033:0x44a789 Code: e8 5c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 2b cc fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fb76ad4bd18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000006dbc58 RCX: 000000000044a789 RDX: 0000000020000280 RSI: 00000000c02064b2 RDI: 0000000000000008 RBP: 00000000006dbc50 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc5c R13: 00007fb76ad4bd20 R14: 00007fb76ad4bd20 R15: 20c49ba5e353f7cf Allocated by task 8902: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 kmem_cache_alloc_trace+0x152/0x740 mm/slab.c:3625 kmalloc include/linux/slab.h:515 [inline] kzalloc include/linux/slab.h:709 [inline] __vgem_gem_create+0x47/0xd0 drivers/gpu/drm/vgem/vgem_drv.c:158 vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:187 [inline] vgem_gem_dumb_create+0xba/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:210 drm_mode_create_dumb+0x1ea/0x2b0 drivers/gpu/drm/drm_dumb_buffers.c:92 drm_mode_create_dumb_ioctl+0x9/0x10 drivers/gpu/drm/drm_dumb_buffers.c:98 drm_ioctl_kernel+0x1ab/0x240 drivers/gpu/drm/drm_ioctl.c:752 drm_ioctl+0x47f/0xa00 drivers/gpu/drm/drm_ioctl.c:852 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 Freed by task 8902: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kfree+0xcf/0x220 mm/slab.c:3822 vgem_gem_free_object+0xa7/0xd0 drivers/gpu/drm/vgem/vgem_drv.c:61 drm_gem_object_free+0x89/0x1a0 drivers/gpu/drm/drm_gem.c:839 kref_put include/linux/kref.h:70 [inline] drm_gem_object_put_unlocked+0x102/0x130 drivers/gpu/drm/drm_gem.c:868 vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:192 [inline] vgem_gem_dumb_create+0xed/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:210 drm_mode_create_dumb+0x1ea/0x2b0 drivers/gpu/drm/drm_dumb_buffers.c:92 drm_mode_create_dumb_ioctl+0x9/0x10 drivers/gpu/drm/drm_dumb_buffers.c:98 drm_ioctl_kernel+0x1ab/0x240 drivers/gpu/drm/drm_ioctl.c:752 drm_ioctl+0x47f/0xa00 drivers/gpu/drm/drm_ioctl.c:852 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 The buggy address belongs to the object at ffff88808b8e3d00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 256 bytes inside of 512-byte region [ffff88808b8e3d00, ffff88808b8e3f00) The buggy address belongs to the page: page:ffffea00022e38c0 count:1 mapcount:0 mapping:ffff88812c29c940 index:0x0 flags: 0xfffe0000000100(slab) raw: 00fffe0000000100 ffffea00022b5708 ffff88812c294748 ffff88812c29c940 raw: 0000000000000000 ffff88808b8e3080 0000000100000006 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88808b8e3d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808b8e3d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88808b8e3e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88808b8e3e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88808b8e3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================