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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+0x1103/0x13a0 fs/minix/itree_common.c:160
Read of size 2 at addr ffff88808573918a by task syz-executor001/6969

CPU: 1 PID: 6969 Comm: syz-executor001 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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 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+0x1103/0x13a0 fs/minix/itree_common.c:160
 minix_get_block+0xe5/0x110 fs/minix/inode.c:376
 __block_write_begin_int+0x464/0x1a80 fs/buffer.c:2012
 __block_write_begin fs/buffer.c:2062 [inline]
 block_write_begin+0x58/0x2e0 fs/buffer.c:2121
 minix_write_begin+0x35/0x220 fs/minix/inode.c:412
 generic_perform_write+0x20a/0x4f0 mm/filemap.c:3318
 __generic_file_write_iter+0x24b/0x610 mm/filemap.c:3447
 generic_file_write_iter+0x3a6/0x5c0 mm/filemap.c:3479
 call_write_iter include/linux/fs.h:1908 [inline]
 new_sync_write+0x422/0x650 fs/read_write.c:503
 __kernel_write+0x3f8/0x500 fs/read_write.c:530
 do_acct_process+0xcc2/0x10c0 kernel/acct.c:522
 slow_acct_process kernel/acct.c:581 [inline]
 acct_process+0x3b7/0x4e6 kernel/acct.c:607
 do_exit+0x197e/0x2a40 kernel/exit.c:795
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x40b/0x1ee0 kernel/signal.c:2743
 do_signal+0x82/0x2520 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:235 [inline]
 __prepare_exit_to_usermode+0x156/0x1f0 arch/x86/entry/common.c:269
 do_syscall_64+0x6c/0xe0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x44b489
Code: Bad RIP value.
RSP: 002b:00007f77f60eacf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00000000006ddc38 RCX: 000000000044b489
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000006ddc3c
RBP: 00000000006ddc30 R08: 00000000006ddc30 R09: 0000000000000000
R10: 00007f77f60eabc0 R11: 0000000000000246 R12: 00000000006ddc3c
R13: 00007fffaf029adf R14: 00007f77f60eb9c0 R15: 0000000000000001

The buggy address belongs to the page:
page:ffffea000215ce40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea000215f848 ffff8880ae739608 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888085739080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888085739100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888085739180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff888085739200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888085739280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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