Process accounting resumed
==================================================================
BUG: KASAN: use-after-free in add_chain fs/minix/itree_common.c:14 [inline]
BUG: KASAN: use-after-free in get_branch fs/minix/itree_common.c:52 [inline]
BUG: KASAN: use-after-free in get_block+0x69a/0x1600 fs/minix/itree_common.c:160
Read of size 2 at addr ffff88807f15c18a by task syz-executor.1/9979

CPU: 1 PID: 9979 Comm: syz-executor.1 Not tainted 5.8.0-rc4-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+0x1f0/0x31e lib/dump_stack.c:118
 print_address_description+0x66/0x5a0 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 add_chain fs/minix/itree_common.c:14 [inline]
 get_branch fs/minix/itree_common.c:52 [inline]
 get_block+0x69a/0x1600 fs/minix/itree_common.c:160
 __block_write_begin_int+0x708/0x1a00 fs/buffer.c:2012
 __block_write_begin fs/buffer.c:2062 [inline]
 block_write_begin+0x59/0x280 fs/buffer.c:2121
 minix_write_begin+0x38/0x1f0 fs/minix/inode.c:412
 generic_perform_write+0x23b/0x4e0 mm/filemap.c:3318
 __generic_file_write_iter+0x22b/0x4e0 mm/filemap.c:3447
 generic_file_write_iter+0x4a6/0x650 mm/filemap.c:3479
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 __kernel_write+0x85b/0xa60 fs/read_write.c:530
 do_acct_process+0xec6/0x12b0 kernel/acct.c:522
 acct_pin_kill+0x27/0x130 kernel/acct.c:174
 pin_kill+0x218/0x6a0 fs/fs_pin.c:44
 mnt_pin_kill+0x9d/0x160 fs/fs_pin.c:81
 cleanup_mnt+0x48c/0x4e0 fs/namespace.c:1111
 task_work_run+0x137/0x1c0 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:239 [inline]
 __prepare_exit_to_usermode+0x14c/0x1e0 arch/x86/entry/common.c:269
 do_syscall_64+0x7f/0xe0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cba9
Code: Bad RIP value.
RSP: 002b:00007f426b9aec78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 000000000050ca80 RCX: 000000000045cba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000500
RBP: 000000000078c0e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000cb6 R14: 00000000004cf091 R15: 00007f426b9af6d4

The buggy address belongs to the page:
page:ffffea0001fc5700 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x1
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea00021b6f08 ffffea0001fc2008 0000000000000000
raw: 0000000000000001 0000000000000002 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88807f15c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807f15c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807f15c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88807f15c200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807f15c280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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