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BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x615/0xab0 fs/reiserfs/lbalance.c:-1
Read of size 48 at addr ffff888058692ff0 by task syz.4.1140/8000

CPU: 1 PID: 8000 Comm: syz.4.1140 Not tainted 5.15.188-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x27b/0x290 mm/kasan/generic.c:189
 memcpy+0x25/0x60 mm/kasan/shadow.c:65
 leaf_paste_in_buffer+0x615/0xab0 fs/reiserfs/lbalance.c:-1
 leaf_copy_dir_entries+0x56c/0x8f0 fs/reiserfs/lbalance.c:108
 leaf_copy_boundary_item+0xb8c/0x2190 fs/reiserfs/lbalance.c:168
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0x84a/0xde0 fs/reiserfs/lbalance.c:726
 leaf_shift_left+0xb9/0x450 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+0x1dbd/0x10e60 fs/reiserfs/do_balan.c:1393
 do_balance+0x2fa/0x930 fs/reiserfs/do_balan.c:1888
 reiserfs_cut_from_item+0x1391/0x1ef0 fs/reiserfs/stree.c:1838
 reiserfs_do_truncate+0xa90/0x13e0 fs/reiserfs/stree.c:1973
 reiserfs_truncate_file+0x632/0xdc0 fs/reiserfs/inode.c:2318
 reiserfs_setattr+0xaa7/0x1010 fs/reiserfs/inode.c:3409
 notify_change+0xbcd/0xee0 fs/attr.c:505
 do_truncate+0x197/0x220 fs/open.c:65
 handle_truncate fs/namei.c:3265 [inline]
 do_open fs/namei.c:3612 [inline]
 path_openat+0x28af/0x2f30 fs/namei.c:3742
 do_filp_open+0x1b3/0x3e0 fs/namei.c:3769
 do_sys_openat2+0x142/0x4a0 fs/open.c:1253
 do_sys_open fs/open.c:1269 [inline]
 __do_sys_creat fs/open.c:1345 [inline]
 __se_sys_creat fs/open.c:1339 [inline]
 __x64_sys_creat+0x8c/0xb0 fs/open.c:1339
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f210eb1c929
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:00007f210dd8c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007f210ed43fa0 RCX: 00007f210eb1c929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000000c0
RBP: 00007f210eb9eb39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f210ed43fa0 R15: 00007ffd8cd0c688
 </TASK>

The buggy address belongs to the page:
page:ffffea000161a480 refcount:2 mapcount:0 mapping:ffff888016d288b0 index:0x21c pfn:0x58692
memcg:ffff888079318000
aops:def_blk_aops ino:700004
flags: 0xfff00000002032(referenced|lru|active|private|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000002032 ffffea000158f248 ffff88801d0d7030 ffff888016d288b0
raw: 000000000000021c ffff888074f4abc8 00000002ffffffff ffff888079318000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x108c48(GFP_NOFS|__GFP_NOFAIL|__GFP_HARDWALL|__GFP_MOVABLE), pid 8000, ts 633772248739, free_ts 633761814623
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5474
 __page_cache_alloc+0xd2/0x3f0 mm/filemap.c:1022
 pagecache_get_page+0x986/0xef0 mm/filemap.c:1940
 find_or_create_page include/linux/pagemap.h:420 [inline]
 grow_dev_page fs/buffer.c:949 [inline]
 grow_buffers fs/buffer.c:1014 [inline]
 __getblk_slow fs/buffer.c:1041 [inline]
 __getblk_gfp+0x249/0xb70 fs/buffer.c:1336
 sb_getblk include/linux/buffer_head.h:361 [inline]
 get_empty_nodes+0x511/0x8c0 fs/reiserfs/fix_node.c:890
 fix_nodes+0x1e69/0x82d0 fs/reiserfs/fix_node.c:2662
 reiserfs_paste_into_item+0x5c8/0x7e0 fs/reiserfs/stree.c:2130
 reiserfs_get_block+0x1bde/0x4100 fs/reiserfs/inode.c:1077
 __block_write_begin_int+0x54e/0x15a0 fs/buffer.c:2012
 reiserfs_write_begin+0x34b/0x810 fs/reiserfs/inode.c:2790
 generic_cont_expand_simple+0xe9/0x190 fs/buffer.c:2362
 reiserfs_setattr+0x42f/0x1010 fs/reiserfs/inode.c:3319
 notify_change+0xbcd/0xee0 fs/attr.c:505
 do_truncate+0x197/0x220 fs/open.c:65
 do_sys_ftruncate+0x31b/0x3d0 fs/open.c:193
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+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x122/0x7e0 mm/page_alloc.c:3433
 release_pages+0x184b/0x1bb0 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 mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x164/0x2e0 mm/mmu_gather.c:338
 unmap_region+0x315/0x360 mm/mmap.c:2665
 __do_munmap+0x9d3/0xdc0 mm/mmap.c:2895
 __vm_munmap+0x137/0x230 mm/mmap.c:2948
 __do_sys_munmap mm/mmap.c:2974 [inline]
 __se_sys_munmap mm/mmap.c:2970 [inline]
 __x64_sys_munmap+0x67/0x70 mm/mmap.c:2970
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff888058692f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888058692f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888058693000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888058693080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888058693100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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