==================================================================
BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x198/0xa0c fs/reiserfs/lbalance.c:1017
Write of size 3936 at addr ffff0000f41ce140 by task syz.7.201/5308

CPU: 0 PID: 5308 Comm: syz.7.201 Not tainted 5.15.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x78/0x30c mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xec/0x15c mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x270/0x2b0 mm/kasan/generic.c:189
 memmove+0xb4/0xe8 mm/kasan/shadow.c:55
 leaf_paste_in_buffer+0x198/0xa0c 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+0x260/0x778 fs/reiserfs/do_balan.c:1888
 reiserfs_paste_into_item+0x5b4/0x6d0 fs/reiserfs/stree.c:2159
 reiserfs_get_block+0x1458/0x34b0 fs/reiserfs/inode.c:1077
 __block_write_begin_int+0x3e4/0x1588 fs/buffer.c:2012
 __block_write_begin+0x40/0x54 fs/buffer.c:2062
 reiserfs_write_begin+0x3c8/0x654 fs/reiserfs/inode.c:2790
 generic_perform_write+0x204/0x480 mm/filemap.c:3785
 __generic_file_write_iter+0x23c/0x454 mm/filemap.c:3912
 generic_file_write_iter+0xb0/0x1b4 mm/filemap.c:3944
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x7c8/0xa2c fs/read_write.c:594
 ksys_write+0x120/0x210 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

The buggy address belongs to the page:
page:00000000d9824f0a refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1341ce
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc0003c41c48 fffffc0003d07348 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000f41ce000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000f41ce080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000f41ce100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff0000f41ce180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000f41ce200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
Unable to handle kernel write to read-only memory at virtual address ffff000163820000