bisecting fixing commit since fbc5fe7a54d02e11972e3b2a5ddb6ffc88162c8f building syzkaller on 0ecb9746a701be4544b845514a31a21cce92cc79 testing commit fbc5fe7a54d02e11972e3b2a5ddb6ffc88162c8f with gcc (GCC) 8.1.0 kernel signature: c29f62863dfcb8d52dbd84ab8bceabbeb8a2514a62b14fe30a5ba683281e4040 run #0: crashed: KASAN: use-after-free Read in soft_cursor run #1: crashed: KASAN: use-after-free Read in soft_cursor run #2: crashed: KASAN: use-after-free Read in soft_cursor run #3: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #4: crashed: KASAN: use-after-free Read in soft_cursor run #5: crashed: KASAN: use-after-free Read in soft_cursor run #6: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #7: crashed: KASAN: use-after-free Read in soft_cursor run #8: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #9: crashed: KASAN: use-after-free Read in soft_cursor testing current HEAD ab9dfda232481dcfaf549ce774004d116fc80c13 testing commit ab9dfda232481dcfaf549ce774004d116fc80c13 with gcc (GCC) 8.1.0 kernel signature: 79b166a77c83d06369db63b97ed3385c1f17bdde80a91ba686da36104985e628 run #0: crashed: KASAN: use-after-free Read in soft_cursor run #1: crashed: KASAN: use-after-free Read in soft_cursor run #2: crashed: KASAN: use-after-free Read in soft_cursor run #3: crashed: KASAN: use-after-free Read in soft_cursor run #4: crashed: KASAN: use-after-free Read in soft_cursor run #5: crashed: KASAN: use-after-free Read in soft_cursor run #6: crashed: KASAN: use-after-free Read in soft_cursor run #7: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #8: crashed: KASAN: use-after-free Read in soft_cursor run #9: crashed: KASAN: slab-out-of-bounds Read in soft_cursor revisions tested: 2, total time: 25m21.228270788s (build: 17m59.535826s, test: 5m59.3785383s) the crash still happens on HEAD commit msg: Linux 4.14.180 crash: KASAN: slab-out-of-bounds Read in soft_cursor IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_1: link becomes ready bridge0: port 2(bridge_slave_1) entered blocking state bridge0: port 2(bridge_slave_1) entered forwarding state ================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:347 [inline] BUG: KASAN: slab-out-of-bounds in soft_cursor+0x430/0xc70 drivers/video/fbdev/core/softcursor.c:70 Read of size 9 at addr ffff88808d45a0d1 by task syz-executor.2/7333 CPU: 0 PID: 7333 Comm: syz-executor.2 Not tainted 4.14.180-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267 memcpy+0x23/0x50 mm/kasan/kasan.c:302 memcpy include/linux/string.h:347 [inline] soft_cursor+0x430/0xc70 drivers/video/fbdev/core/softcursor.c:70 bit_cursor+0xe3b/0x1ce0 drivers/video/fbdev/core/bitblit.c:386 fbcon_cursor+0x3d8/0x6c0 drivers/video/fbdev/core/fbcon.c:1350 hide_cursor+0x73/0x2b0 drivers/tty/vt/vt.c:590 redraw_screen+0x272/0x7f0 drivers/tty/vt/vt.c:680 vc_do_resize+0xc2f/0xfa0 drivers/tty/vt/vt.c:967 vc_resize+0x3d/0x60 drivers/tty/vt/vt.c:987 vt_ioctl+0xee5/0x21f0 drivers/tty/vt/vt_ioctl.c:901 tty_ioctl+0x434/0x1260 drivers/tty/tty_io.c:2661 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x74/0x80 fs/ioctl.c:692 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45a679 RSP: 002b:00007f61bc2dcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a679 RDX: 00000000200002c0 RSI: 000000000000560a RDI: 0000000000000004 RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f61bc2dd6d4 R13: 00000000004c6ce2 R14: 00000000004dd2d0 R15: 00000000ffffffff Allocated by task 2381: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 kmem_cache_alloc+0x12e/0x790 mm/slab.c:3552 kmem_cache_zalloc include/linux/slab.h:651 [inline] fill_pool lib/debugobjects.c:110 [inline] __debug_object_init+0x65c/0xa10 lib/debugobjects.c:341 debug_object_init+0x16/0x20 lib/debugobjects.c:393 debug_timer_init kernel/time/timer.c:687 [inline] debug_init kernel/time/timer.c:736 [inline] init_timer_key+0x2a/0x280 kernel/time/timer.c:780 ipv6_add_addr+0xacc/0x1920 net/ipv6/addrconf.c:1037 addrconf_add_linklocal+0x144/0x2c0 net/ipv6/addrconf.c:3071 addrconf_addr_gen+0x2bf/0x300 net/ipv6/addrconf.c:3201 addrconf_dev_config+0xdc/0x250 net/ipv6/addrconf.c:3246 addrconf_notify+0x2e1/0x1b10 net/ipv6/addrconf.c:3472 notifier_call_chain+0xd6/0x150 kernel/notifier.c:93 __raw_notifier_call_chain kernel/notifier.c:394 [inline] raw_notifier_call_chain+0x11/0x20 kernel/notifier.c:401 call_netdevice_notifiers_info+0x4b/0x60 net/core/dev.c:1671 netdev_state_change+0xb5/0xe0 net/core/dev.c:1318 linkwatch_do_dev+0x72/0xc0 net/core/link_watch.c:164 __linkwatch_run_queue+0x23f/0x450 net/core/link_watch.c:202 linkwatch_event+0x3e/0x50 net/core/link_watch.c:237 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Freed by task 0: (stack is not available) The buggy address belongs to the object at ffff88808d45a0a8 which belongs to the cache debug_objects_cache of size 40 The buggy address is located 1 bytes to the right of 40-byte region [ffff88808d45a0a8, ffff88808d45a0d0) The buggy address belongs to the page: page:ffffea0002351680 count:1 mapcount:0 mapping:ffff88808d45a000 index:0xffff88808d45afb9 flags: 0xfffe0000000100(slab) raw: 00fffe0000000100 ffff88808d45a000 ffff88808d45afb9 0000000100000047 raw: ffffea0002355720 ffffea00023555a0 ffff8880aa810dc0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88808d459f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88808d45a000: 00 00 00 00 00 fc fc 00 00 00 00 00 fc fc 00 00 >ffff88808d45a080: 00 00 00 fc fc 00 00 00 00 00 fc fc 00 00 00 00 ^ ffff88808d45a100: 00 fc fc 00 00 00 00 00 fc fc 00 00 00 00 00 fc ffff88808d45a180: fc 00 00 00 00 00 fc fc 00 00 00 00 00 fc fc 00 ==================================================================