BUG: KASAN: use-after-free in sysv_new_block+0x790/0x970 fs/sysv/balloc.c:113
Read of size 4 at addr ffff888059dc40c8 by task syz.3.4/5929

CPU: 0 UID: 0 PID: 5929 Comm: syz.3.4 Not tainted 6.14.0-rc3-next-20250218-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:410 [inline]
 print_report+0x16b/0x5a0 mm/kasan/report.c:510
 kasan_report+0x143/0x180 mm/kasan/report.c:623
 sysv_new_block+0x790/0x970 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:135 [inline]
 get_block+0x30a/0x16e0 fs/sysv/itree.c:254
 __block_write_begin_int+0x692/0x19a0 fs/buffer.c:2116
 block_write_begin+0x8f/0x120 fs/buffer.c:2226
 sysv_write_begin+0x31/0x70 fs/sysv/itree.c:490
 page_symlink+0x2c0/0x4d0 fs/namei.c:5402
 sysv_symlink+0xcf/0x180 fs/sysv/namei.c:86
 vfs_symlink+0x137/0x2e0 fs/namei.c:4659
 do_symlinkat+0x222/0x3a0 fs/namei.c:4685
 __do_sys_symlink fs/namei.c:4706 [inline]
 __se_sys_symlink fs/namei.c:4704 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4704
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcc15d8d169
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:00007fcc16ca9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007fcc15fa5fa0 RCX: 00007fcc15d8d169
RDX: 0000000000000000 RSI: 000040000000acc0 RDI: 000040000000ad80
RBP: 00007fcc15e0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fcc15fa5fa0 R15: 00007ffe8d932bc8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fcc0b601 pfn:0x59dc4
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00016770c8 ffffea0001677148 0000000000000000
raw: 00000007fcc0b601 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5929, tgid 5928 (syz.3.4), ts 101390398182, free_ts 101394838102
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1629
 prep_new_page mm/page_alloc.c:1637 [inline]
 get_page_from_freelist+0x365c/0x37a0 mm/page_alloc.c:3555
 __alloc_frozen_pages_noprof+0x292/0x710 mm/page_alloc.c:4817
 alloc_pages_mpol+0x311/0x660 mm/mempolicy.c:2301
 folio_alloc_mpol_noprof mm/mempolicy.c:2320 [inline]
 vma_alloc_folio_noprof+0x12b/0x260 mm/mempolicy.c:2355
 folio_prealloc+0x2e/0x170
 alloc_anon_folio mm/memory.c:4823 [inline]
 do_anonymous_page mm/memory.c:4880 [inline]
 do_pte_missing mm/memory.c:4046 [inline]
 handle_pte_fault+0x2e40/0x61c0 mm/memory.c:5890
 __handle_mm_fault mm/memory.c:6033 [inline]
 handle_mm_fault+0x11ae/0x1cd0 mm/memory.c:6202
 do_user_addr_fault arch/x86/mm/fault.c:1337 [inline]
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x459/0x920 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5929 tgid 5928 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1205 [inline]
 free_unref_folios+0xe40/0x18b0 mm/page_alloc.c:2785
 folios_put_refs+0x76c/0x860 mm/swap.c:994
 free_pages_and_swap_cache+0x5c3/0x690 mm/swap_state.c:328
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
 tlb_flush_mmu+0x3a5/0x680 mm/mmu_gather.c:404
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:496
 vms_clear_ptes+0x432/0x530 mm/vma.c:1163
 vms_complete_munmap_vmas+0x210/0x8f0 mm/vma.c:1205
 do_vmi_align_munmap+0x4df/0x5b0 mm/vma.c:1464
 do_vmi_munmap+0x24e/0x2d0 mm/vma.c:1512
 __vm_munmap+0x372/0x510 mm/vma.c:2970
 __do_sys_munmap mm/mmap.c:1084 [inline]
 __se_sys_munmap mm/mmap.c:1081 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1081
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888059dc3f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888059dc4000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888059dc4080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888059dc4100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888059dc4180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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