bisecting fixing commit since a844dc4c544291470aa69edbe2434b040794e269 building syzkaller on 1508f45368a309a3b1196a342b3d64ce7be4cc43 testing commit a844dc4c544291470aa69edbe2434b040794e269 with gcc (GCC) 8.1.0 kernel signature: a91e284586df43565c5fb98c2619c309aa0f491c5ceb7e73d78c5d897580d4cc run #0: crashed: KASAN: use-after-free Write in release_tty run #1: crashed: KASAN: use-after-free Write in release_tty run #2: crashed: KASAN: use-after-free Write in release_tty run #3: crashed: KASAN: use-after-free Write in release_tty run #4: crashed: KASAN: use-after-free Write in release_tty run #5: crashed: KASAN: use-after-free Write in release_tty run #6: crashed: KASAN: use-after-free Write in release_tty run #7: crashed: KASAN: use-after-free Read in tty_buffer_cancel_work run #8: crashed: KASAN: use-after-free Write in release_tty run #9: crashed: KASAN: use-after-free Write in release_tty testing current HEAD 9fa690a2a016e1b55356835f047b952e67d3d73a testing commit 9fa690a2a016e1b55356835f047b952e67d3d73a with gcc (GCC) 8.1.0 kernel signature: 26fc0a61680df84a26f92aa38efe5e652a468b27f752903d2e73a3a934de2911 all runs: crashed: KASAN: use-after-free Write in release_tty revisions tested: 2, total time: 25m57.139687396s (build: 18m6.162166374s, test: 6m42.788654885s) the crash still happens on HEAD commit msg: Linux 4.14.169 crash: KASAN: use-after-free Write in release_tty 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready 8021q: adding VLAN 0 to HW filter on device batadv0 ================================================================== BUG: KASAN: use-after-free in con_shutdown+0x76/0x80 drivers/tty/vt/vt.c:2930 Write of size 8 at addr ffff888098f14b88 by task syz-executor.1/7134 CPU: 1 PID: 7134 Comm: syz-executor.1 Not tainted 4.14.169-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 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435 con_shutdown+0x76/0x80 drivers/tty/vt/vt.c:2930 release_tty+0xab/0x760 drivers/tty/tty_io.c:1501 tty_release_struct+0x33/0x50 drivers/tty/tty_io.c:1616 tty_release+0x97e/0xc60 drivers/tty/tty_io.c:1776 __fput+0x232/0x750 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x16a/0x1b0 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x414291 RSP: 002b:00007ffcb08bbf60 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000414291 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004 RBP: 0000000000000001 R08: ffffffffffffffff R09: ffffffffffffffff R10: 00007ffcb08bc040 R11: 0000000000000293 R12: 000000000075c9a0 R13: 000000000075c9a0 R14: 0000000000760128 R15: 000000000075bf2c Allocated by task 7136: 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 kmem_cache_alloc_trace+0x152/0x7a0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] vc_allocate+0x145/0x590 drivers/tty/vt/vt.c:772 con_install+0x4d/0x410 drivers/tty/vt/vt.c:2881 tty_driver_install_tty drivers/tty/tty_io.c:1225 [inline] tty_init_dev+0xdb/0x350 drivers/tty/tty_io.c:1338 tty_open_by_driver drivers/tty/tty_io.c:1973 [inline] tty_open+0x50a/0x970 drivers/tty/tty_io.c:2021 chrdev_open+0x1e9/0x5b0 fs/char_dev.c:423 do_dentry_open+0x620/0xdb0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:891 do_last fs/namei.c:3428 [inline] path_openat+0xe09/0x3d60 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1c2/0x340 fs/open.c:1084 SYSC_open fs/open.c:1102 [inline] SyS_open+0x19/0x20 fs/open.c:1097 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 7141: 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_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 vt_disallocate_all+0x23b/0x3c0 drivers/tty/vt/vt_ioctl.c:323 vt_ioctl+0x1a1f/0x21d0 drivers/tty/vt/vt_ioctl.c:816 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 The buggy address belongs to the object at ffff888098f14a80 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 264 bytes inside of 2048-byte region [ffff888098f14a80, ffff888098f15280) The buggy address belongs to the page: page:ffffea000263c500 count:1 mapcount:0 mapping:ffff888098f14200 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffff888098f14200 0000000000000000 0000000100000003 raw: ffffea00026adda0 ffffea0001d9bf20 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888098f14a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888098f14b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888098f14b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888098f14c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888098f14c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================