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BUG: KASAN: use-after-free in n_tty_check_throttle drivers/tty/n_tty.c:266 [inline]
BUG: KASAN: use-after-free in n_tty_receive_buf_common+0x214f/0x2570 drivers/tty/n_tty.c:1761
Read of size 1 at addr ffff88803bce427e by task syz-executor.0/22106

CPU: 1 PID: 22106 Comm: syz-executor.0 Not tainted 4.14.171-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+0x142/0x197 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
 n_tty_check_throttle drivers/tty/n_tty.c:266 [inline]
 n_tty_receive_buf_common+0x214f/0x2570 drivers/tty/n_tty.c:1761
 n_tty_receive_buf2+0x34/0x40 drivers/tty/n_tty.c:1777
 tty_ldisc_receive_buf+0xa5/0x1a0 drivers/tty/tty_buffer.c:455
 paste_selection+0x1e6/0x3f2 drivers/tty/vt/selection.c:360
 tioclinux+0x10e/0x400 drivers/tty/vt/vt.c:2696
 vt_ioctl+0x180c/0x2170 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x841/0x1320 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c6c9
RSP: 002b:00007fa9dc67bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa9dc67c6d4 RCX: 000000000045c6c9
RDX: 0000000020000000 RSI: 000000000000541c RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000056c R14: 00000000004c7e83 R15: 000000000076bf2c

Allocated by task 22103:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 __do_kmalloc mm/slab.c:3720 [inline]
 __kmalloc+0x15d/0x7a0 mm/slab.c:3729
 kmalloc include/linux/slab.h:493 [inline]
 set_selection+0x79a/0xe30 drivers/tty/vt/selection.c:295
 tioclinux+0xf7/0x400 drivers/tty/vt/vt.c:2692
 vt_ioctl+0x180c/0x2170 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x841/0x1320 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 22101:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 set_selection+0x7b7/0xe30 drivers/tty/vt/selection.c:301
 tioclinux+0xf7/0x400 drivers/tty/vt/vt.c:2692
 vt_ioctl+0x180c/0x2170 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x841/0x1320 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff88803bce3980
 which belongs to the cache kmalloc-65536 of size 65536
The buggy address is located 2302 bytes inside of
 65536-byte region [ffff88803bce3980, ffff88803bcf3980)
The buggy address belongs to the page:
page:ffffea0000ef3800 count:1 mapcount:0 mapping:ffff88803bce3980 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88803bce3980 0000000000000000 0000000100000001
raw: ffffea0000ef3020 ffff8880aa801e48 ffff8880aa802500 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88803bce4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803bce4180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803bce4200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88803bce4280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803bce4300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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