syzbot

==================================================================
BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x6a1/0xbd0 fs/reiserfs/lbalance.c:-1
Read of size 48 at addr ffff88804f904ff0 by task syz.4.450/7988

CPU: 1 PID: 7988 Comm: syz.4.450 Not tainted 6.6.96-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x230 mm/kasan/report.c:475
 kasan_report+0x117/0x150 mm/kasan/report.c:588
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x288/0x290 mm/kasan/generic.c:187
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 leaf_paste_in_buffer+0x6a1/0xbd0 fs/reiserfs/lbalance.c:-1
 leaf_copy_dir_entries+0x5e7/0x990 fs/reiserfs/lbalance.c:108
 leaf_copy_boundary_item+0xb90/0x2180 fs/reiserfs/lbalance.c:168
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0x8b5/0xe90 fs/reiserfs/lbalance.c:726
 leaf_shift_left+0xbd/0x450 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+0x1dc1/0x10da0 fs/reiserfs/do_balan.c:1393
 do_balance+0x2fe/0x940 fs/reiserfs/do_balan.c:1888
 reiserfs_delete_solid_item+0x8b5/0xec0 fs/reiserfs/stree.c:1460
 remove_save_link+0x25a/0x3c0 fs/reiserfs/super.c:540
 reiserfs_truncate_file+0x561/0x7c0 fs/reiserfs/inode.c:2318
 reiserfs_setattr+0xc0c/0x11a0 fs/reiserfs/inode.c:3392
 notify_change+0xb0d/0xe10 fs/attr.c:499
 do_truncate+0x19b/0x220 fs/open.c:66
 vfs_truncate+0x266/0x300 fs/open.c:112
 do_sys_truncate+0xe0/0x1a0 fs/open.c:135
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe851b8e929
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:00007fe85291b038 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007fe851db6080 RCX: 00007fe851b8e929
RDX: 0000000000000000 RSI: 00000000003a6000 RDI: 0000200000000080
RBP: 00007fe851c10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fe851db6080 R15: 00007ffca04688c8
 </TASK>

The buggy address belongs to the physical page:
page:ffffea00013e4100 refcount:2 mapcount:0 mapping:ffff88801fea58f8 index:0x215 pfn:0x4f904
memcg:ffff88807dde6000
aops:def_blk_aops ino:700004
flags: 0xfff50000008224(referenced|lru|workingset|private|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff50000008224 ffffea0001573e88 ffffea00015d3308 ffff88801fea58f8
raw: 0000000000000215 ffff88805aeec740 00000002ffffffff ffff88807dde6000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x148c48(GFP_NOFS|__GFP_NOFAIL|__GFP_COMP|__GFP_HARDWALL|__GFP_MOVABLE), pid 7989, tgid 7984 (syz.4.450), ts 221684318736, free_ts 221565809829
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 folio_alloc+0x1e/0x30 mm/mempolicy.c:2291
 filemap_alloc_folio+0xdf/0x470 mm/filemap.c:1004
 __filemap_get_folio+0x3ee/0xbc0 mm/filemap.c:1962
 grow_dev_page fs/buffer.c:1058 [inline]
 grow_buffers fs/buffer.c:1118 [inline]
 __getblk_slow fs/buffer.c:1145 [inline]
 __getblk_gfp+0x223/0x660 fs/buffer.c:1439
 sb_getblk include/linux/buffer_head.h:344 [inline]
 get_empty_nodes+0x515/0x8c0 fs/reiserfs/fix_node.c:890
 fix_nodes+0x1e52/0x82e0 fs/reiserfs/fix_node.c:2663
 reiserfs_insert_item+0x9a1/0xbe0 fs/reiserfs/stree.c:2238
 reiserfs_new_inode+0xf67/0x17d0 fs/reiserfs/inode.c:2052
 reiserfs_create+0x3be/0x680 fs/reiserfs/namei.c:666
 lookup_open fs/namei.c:3488 [inline]
 open_last_lookups fs/namei.c:3556 [inline]
 path_openat+0x1277/0x3190 fs/namei.c:3786
 do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
 do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
 do_sys_open fs/open.c:1434 [inline]
 __do_sys_openat fs/open.c:1450 [inline]
 __se_sys_openat fs/open.c:1445 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1445
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 tlb_batch_pages_flush mm/mmu_gather.c:98 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:293 [inline]
 tlb_flush_mmu+0x368/0x4f0 mm/mmu_gather.c:300
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:392
 unmap_region+0x2ed/0x340 mm/mmap.c:2345
 do_vmi_align_munmap+0xffe/0x1660 mm/mmap.c:2588
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2656
 __vm_munmap+0x193/0x3c0 mm/mmap.c:2957
 __do_sys_munmap mm/mmap.c:2974 [inline]
 __se_sys_munmap mm/mmap.c:2971 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:2971
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88804f904f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88804f904f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88804f905000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88804f905080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804f905100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================