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BUG: KASAN: use-after-free in n_tty_check_throttle drivers/tty/n_tty.c:264 [inline]
BUG: KASAN: use-after-free in n_tty_receive_buf_common+0x264d/0x2a50 drivers/tty/n_tty.c:1759
Read of size 1 at addr ffff8880493d1934 by task syz-executor.1/31373

CPU: 1 PID: 31373 Comm: syz-executor.1 Not tainted 4.19.107-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+0x188/0x20d lib/dump_stack.c:118
 print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
 n_tty_check_throttle drivers/tty/n_tty.c:264 [inline]
 n_tty_receive_buf_common+0x264d/0x2a50 drivers/tty/n_tty.c:1759
 tty_ldisc_receive_buf+0xa9/0x190 drivers/tty/tty_buffer.c:456
 paste_selection+0x1d7/0x433 drivers/tty/vt/selection.c:366
 tioclinux+0x12c/0x480 drivers/tty/vt/vt.c:3030
 vt_ioctl+0x1811/0x2310 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x7a1/0x1420 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcda/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c479
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f47be892c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f47be8936d4 RCX: 000000000045c479
RDX: 0000000020000100 RSI: 000000000000541c RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000574 R14: 00000000004c7c8f R15: 000000000076bf2c

Allocated by task 31325:
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
 __do_kmalloc mm/slab.c:3727 [inline]
 __kmalloc+0x15b/0x770 mm/slab.c:3736
 kmalloc_array include/linux/slab.h:637 [inline]
 set_selection+0x7d4/0x1200 drivers/tty/vt/selection.c:295
 tioclinux+0x115/0x480 drivers/tty/vt/vt.c:3026
 vt_ioctl+0x1811/0x2310 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x7a1/0x1420 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcda/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 31374:
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xce/0x220 mm/slab.c:3822
 set_selection+0x7f1/0x1200 drivers/tty/vt/selection.c:302
 tioclinux+0x115/0x480 drivers/tty/vt/vt.c:3026
 vt_ioctl+0x1811/0x2310 drivers/tty/vt/vt_ioctl.c:364
 tty_ioctl+0x7a1/0x1420 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcda/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880493d1640
 which belongs to the cache kmalloc-32768 of size 32768
The buggy address is located 756 bytes inside of
 32768-byte region [ffff8880493d1640, ffff8880493d9640)
The buggy address belongs to the page:
page:ffffea000124f400 count:1 mapcount:0 mapping:ffff88812c3d5380 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea0000fe0408 ffff88812c3d4d48 ffff88812c3d5380
raw: 0000000000000000 ffff8880493d1640 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880493d1800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880493d1880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880493d1900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8880493d1980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880493d1a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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