==================================================================
BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x5d0/0xa40 fs/reiserfs/lbalance.c:1043
Read of size 48 at addr ffff0000f6a85ff0 by task syz.5.381/6312

CPU: 1 PID: 6312 Comm: syz.5.381 Tainted: G   M               syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 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+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x258/0x290 mm/kasan/generic.c:189
 memcpy+0x48/0x90 mm/kasan/shadow.c:65
 leaf_paste_in_buffer+0x5d0/0xa40 fs/reiserfs/lbalance.c:1043
 leaf_copy_dir_entries+0x444/0x780 fs/reiserfs/lbalance.c:108
 leaf_copy_boundary_item+0x87c/0x19f4 fs/reiserfs/lbalance.c:-1
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0x6c8/0xbd8 fs/reiserfs/lbalance.c:726
 balance_leaf_when_delete_left fs/reiserfs/do_balan.c:167 [inline]
 balance_leaf_when_delete fs/reiserfs/do_balan.c:272 [inline]
 balance_leaf+0x9800/0xdee0 fs/reiserfs/do_balan.c:1393
 do_balance+0x270/0x794 fs/reiserfs/do_balan.c:1888
 reiserfs_cut_from_item+0x1160/0x1a34 fs/reiserfs/stree.c:1838
 reiserfs_do_truncate+0x728/0xfd0 fs/reiserfs/stree.c:1973
 reiserfs_truncate_file+0x3a4/0xb04 fs/reiserfs/inode.c:2310
 reiserfs_setattr+0xad4/0x1014 fs/reiserfs/inode.c:3395
 notify_change+0xb5c/0xe20 fs/attr.c:499
 do_truncate+0x188/0x20c fs/open.c:65
 handle_truncate fs/namei.c:3293 [inline]
 do_open fs/namei.c:3638 [inline]
 path_openat+0x21c8/0x27a0 fs/namei.c:3791
 do_filp_open+0x198/0x38c fs/namei.c:3818
 do_sys_openat2+0x134/0x3fc fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __arm64_sys_openat+0x11c/0x150 fs/open.c:1347
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 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:00000000a6a720ee refcount:2 mapcount:0 mapping:00000000f3ef0909 index:0x247 pfn:0x136a85
memcg:ffff0000dda8e000
aops:def_blk_aops ino:700005
flags: 0x5ffd60000002052(referenced|lru|workingset|private|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffd60000002052 fffffc0003daa108 ffff0000cc5ae208 ffff0000c983f618
raw: 0000000000000247 ffff0000c56b81d0 00000002ffffffff ffff0000dda8e000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000f6a85f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff0000f6a85f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000f6a86000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff0000f6a86080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000f6a86100: 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 ffff0000e3e86ff0