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BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x64f/0xaf0 fs/reiserfs/lbalance.c:1037
Write of size 428 at addr ffff888055791e54 by task syz.2.72/4556

CPU: 1 PID: 4556 Comm: syz.2.72 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 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+0x235/0x290 mm/kasan/generic.c:189
 memcpy+0x3c/0x60 mm/kasan/shadow.c:66
 leaf_paste_in_buffer+0x64f/0xaf0 fs/reiserfs/lbalance.c:1037
 leaf_copy_boundary_item+0xc8f/0x21e0 fs/reiserfs/lbalance.c:199
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0x85f/0xe00 fs/reiserfs/lbalance.c:726
 leaf_shift_left+0xb1/0x3f0 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+0x5072/0x10ec0 fs/reiserfs/do_balan.c:1409
 do_balance+0x318/0x930 fs/reiserfs/do_balan.c:1888
 reiserfs_paste_into_item+0x744/0x7f0 fs/reiserfs/stree.c:2159
 reiserfs_get_block+0x1c3d/0x4360 fs/reiserfs/inode.c:1077
 __block_write_begin_int+0x565/0x15d0 fs/buffer.c:2012
 reiserfs_write_begin+0x353/0x820 fs/reiserfs/inode.c:2790
 generic_perform_write+0x2b6/0x550 mm/filemap.c:3785
 __generic_file_write_iter+0x261/0x4e0 mm/filemap.c:3912
 generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
 do_iter_readv_writev+0x47d/0x5f0 fs/read_write.c:-1
 do_iter_write+0x1f8/0x7a0 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_pwritev+0x241/0x3a0 fs/read_write.c:1025
 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: 0033:0x7eff64f8fe59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007eff631e8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000148
RAX: ffffffffffffffda RBX: 00007eff65217fa0 RCX: 00007eff64f8fe59
RDX: 0000000000000001 RSI: 0000200000000000 RDI: 0000000000000004
RBP: 00007eff65025e6f R08: 000000000000000c R09: 0000000000000005
R10: 0000000000800fff R11: 0000000000000246 R12: 0000000000000000
R13: 00007eff65218038 R14: 00007eff65217fa0 R15: 00007ffc4ea914a8
 </TASK>

The buggy address belongs to the page:
page:ffffea000155e440 refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x55791
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000100 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 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 4527, ts 92525410486, free_ts 94390861957
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_pages_vma+0x2bc/0x790 mm/mempolicy.c:2146
 shmem_alloc_page mm/shmem.c:1586 [inline]
 shmem_alloc_and_acct_page+0x47f/0xbe0 mm/shmem.c:1611
 shmem_getpage_gfp+0x14be/0x2c10 mm/shmem.c:1906
 shmem_getpage mm/shmem.c:151 [inline]
 shmem_write_begin+0xcd/0x1a0 mm/shmem.c:2474
 generic_perform_write+0x2b6/0x550 mm/filemap.c:3785
 __generic_file_write_iter+0x261/0x4e0 mm/filemap.c:3912
 generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 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
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+0x119/0x830 mm/page_alloc.c:3433
 release_pages+0x185f/0x1bd0 mm/swap.c:963
 __pagevec_release+0x6d/0xe0 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x5cd/0x19a0 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x1e2/0x9a0 mm/shmem.c:1145
 evict+0x4b6/0x8b0 fs/inode.c:647
 __dentry_kill+0x412/0x630 fs/dcache.c:586
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x5a5/0x8c0 fs/file_table.c:319
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86

Memory state around the buggy address:
 ffff888055791d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888055791d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888055791e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                 ^
 ffff888055791e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888055791f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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