==================================================================
BUG: KASAN: use-after-free in leaf_paste_entries+0x64b/0x13a0 fs/reiserfs/lbalance.c:1362
Read of size 2 at addr ffff888070023008 by task syz.2.795/5700

CPU: 0 PID: 5700 Comm: syz.2.795 Not tainted 5.15.164-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 print_address_description+0x63/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0x16b/0x1c0 mm/kasan/report.c:451
 leaf_paste_entries+0x64b/0x13a0 fs/reiserfs/lbalance.c:1362
 leaf_copy_dir_entries+0x7ec/0xc60 fs/reiserfs/lbalance.c:119
 leaf_copy_boundary_item+0xbbe/0x21b0 fs/reiserfs/lbalance.c:168
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0xcd0/0x28a0 fs/reiserfs/lbalance.c:726
 leaf_shift_left+0xba/0x430 fs/reiserfs/lbalance.c:750
 balance_leaf_when_delete_left fs/reiserfs/do_balan.c:194 [inline]
 balance_leaf_when_delete fs/reiserfs/do_balan.c:272 [inline]
 balance_leaf+0x228e/0x12510 fs/reiserfs/do_balan.c:1393
 do_balance+0x309/0x8f0 fs/reiserfs/do_balan.c:1888
 reiserfs_cut_from_item+0x1945/0x2560 fs/reiserfs/stree.c:1838
 reiserfs_do_truncate+0xa12/0x15b0 fs/reiserfs/stree.c:1973
 reiserfs_truncate_file+0x638/0xda0 fs/reiserfs/inode.c:2318
 reiserfs_setattr+0xa4d/0xf90 fs/reiserfs/inode.c:3409
 notify_change+0xc6d/0xf50 fs/attr.c:505
 do_truncate+0x21c/0x300 fs/open.c:65
 handle_truncate fs/namei.c:3265 [inline]
 do_open fs/namei.c:3612 [inline]
 path_openat+0x28a3/0x2f20 fs/namei.c:3742
 do_filp_open+0x21c/0x460 fs/namei.c:3769
 do_sys_openat2+0x13b/0x4f0 fs/open.c:1253
 do_sys_open fs/open.c:1269 [inline]
 __do_sys_openat fs/open.c:1285 [inline]
 __se_sys_openat fs/open.c:1280 [inline]
 __x64_sys_openat+0x243/0x290 fs/open.c:1280
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe1f5bae9f9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe1f402d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fe1f5d3cf80 RCX: 00007fe1f5bae9f9
RDX: 000000000000275a RSI: 0000000020000040 RDI: ffffffffffffff9c
RBP: 00007fe1f5c1c8ee R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe1f5d3cf80 R15: 00007fffecc9c718
 </TASK>

The buggy address belongs to the page:
page:ffffea0001c008c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x70023
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001c30948 ffffea0001c6f8c8 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x1100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 5601, ts 151773017082, free_ts 153446843489
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x322a/0x33c0 mm/page_alloc.c:4159
 __alloc_pages+0x272/0x700 mm/page_alloc.c:5423
 alloc_pages_vma+0x39a/0x800 mm/mempolicy.c:2146
 wp_page_copy+0x221/0x2070 mm/memory.c:3021
 handle_pte_fault mm/memory.c:4639 [inline]
 __handle_mm_fault mm/memory.c:4756 [inline]
 handle_mm_fault+0x2a3d/0x5950 mm/memory.c:4854
 do_user_addr_fault arch/x86/mm/fault.c:1357 [inline]
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x271/0x700 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:568
 copy_user_enhanced_fast_string+0xe/0x40 arch/x86/lib/copy_user_64.S:205
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 copyout lib/iov_iter.c:157 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:228 [inline]
 __copy_page_to_iter lib/iov_iter.c:861 [inline]
 copy_page_to_iter+0x49a/0x10d0 lib/iov_iter.c:889
 process_vm_rw_pages mm/process_vm_access.c:45 [inline]
 process_vm_rw_single_vec mm/process_vm_access.c:117 [inline]
 process_vm_rw_core mm/process_vm_access.c:215 [inline]
 process_vm_rw+0x886/0xcc0 mm/process_vm_access.c:283
 __do_sys_process_vm_readv mm/process_vm_access.c:295 [inline]
 __se_sys_process_vm_readv mm/process_vm_access.c:291 [inline]
 __x64_sys_process_vm_readv+0xdc/0xf0 mm/process_vm_access.c:291
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0xc34/0xcf0 mm/page_alloc.c:3317
 free_unref_page_list+0x1f7/0x8e0 mm/page_alloc.c:3433
 release_pages+0x1bb9/0x1f40 mm/swap.c:963
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu+0xc8/0x170 mm/mmu_gather.c:247
 zap_pte_range mm/memory.c:1445 [inline]
 zap_pmd_range mm/memory.c:1494 [inline]
 zap_pud_range mm/memory.c:1523 [inline]
 zap_p4d_range mm/memory.c:1544 [inline]
 unmap_page_range+0x214d/0x2630 mm/memory.c:1565
 unmap_vmas+0x1f8/0x390 mm/memory.c:1642
 exit_mmap+0x3b6/0x670 mm/mmap.c:3186
 __mmput+0x112/0x3b0 kernel/fork.c:1126
 exit_mm+0x688/0x7f0 kernel/exit.c:550
 do_exit+0x626/0x2480 kernel/exit.c:861
 do_group_exit+0x144/0x310 kernel/exit.c:996
 get_signal+0xc66/0x14e0 kernel/signal.c:2889
 arch_do_signal_or_restart+0xc3/0x1890 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x97/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307

Memory state around the buggy address:
 ffff888070022f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888070022f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888070023000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff888070023080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888070023100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================