==================================================================
BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x1c8/0xa14 fs/reiserfs/lbalance.c:1017
Write of size 3936 at addr ffff0000e1f5e140 by task syz.3.123/4758

CPU: 0 PID: 4758 Comm: syz.3.123 Not tainted 6.1.138-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x88/0x220 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:427
 kasan_report+0xa8/0x100 mm/kasan/report.c:531
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x260/0x2a0 mm/kasan/generic.c:189
 memmove+0x60/0x90 mm/kasan/shadow.c:55
 leaf_paste_in_buffer+0x1c8/0xa14 fs/reiserfs/lbalance.c:1017
 leaf_copy_boundary_item+0x930/0x19dc fs/reiserfs/lbalance.c:199
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0x694/0xb9c fs/reiserfs/lbalance.c:726
 leaf_shift_left+0xc8/0x3ac fs/reiserfs/lbalance.c:750
 balance_leaf_paste_left_shift fs/reiserfs/do_balan.c:458 [inline]
 balance_leaf_paste_left fs/reiserfs/do_balan.c:592 [inline]
 balance_leaf_left fs/reiserfs/do_balan.c:613 [inline]
 balance_leaf+0x21f8/0xd2f4 fs/reiserfs/do_balan.c:1409
 do_balance+0x260/0x774 fs/reiserfs/do_balan.c:1888
 reiserfs_paste_into_item+0x5b4/0x6d0 fs/reiserfs/stree.c:2159
 reiserfs_get_block+0x1444/0x3524 fs/reiserfs/inode.c:1069
 __block_write_begin_int+0x34c/0x13b8 fs/buffer.c:1991
 __block_write_begin+0x7c/0xa0 fs/buffer.c:2041
 reiserfs_write_begin+0x328/0x71c fs/reiserfs/inode.c:2775
 generic_perform_write+0x230/0x4b0 mm/filemap.c:3846
 __generic_file_write_iter+0x168/0x37c mm/filemap.c:3974
 generic_file_write_iter+0xb4/0x2b0 mm/filemap.c:4006
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ac/0x7c4 fs/read_write.c:584
 ksys_write+0x120/0x210 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the physical page:
page:000000006b89c620 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x121f5e
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc000387d6c8 fffffc0003d82888 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000e1f5e000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e1f5e080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000e1f5e100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff0000e1f5e180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e1f5e200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================