loop2: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop2, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_block+0x790/0x970 fs/sysv/balloc.c:113
Read of size 4 at addr ffff88806e7290c8 by task syz.2.18/6040

CPU: 0 UID: 0 PID: 6040 Comm: syz.2.18 Not tainted 6.13.0-syzkaller-09760-g69e858e0b8b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 sysv_new_block+0x790/0x970 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:135 [inline]
 get_block+0x30a/0x16d0 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+0x2a6/0x4a0 fs/namei.c:5422
 sysv_symlink+0xcf/0x180 fs/sysv/namei.c:86
 vfs_symlink+0x137/0x2e0 fs/namei.c:4671
 do_symlinkat+0x222/0x3a0 fs/namei.c:4697
 __do_sys_symlink fs/namei.c:4718 [inline]
 __se_sys_symlink fs/namei.c:4716 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4716
 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: 0033:0x7f3a41d8cda9
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:00007f3a42c19038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f3a41fa5fa0 RCX: 00007f3a41d8cda9
RDX: 0000000000000000 RSI: 000000002000acc0 RDI: 000000002000ad80
RBP: 00007f3a41e0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3a41fa5fa0 R15: 00007ffd5cb3b8f8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xc pfn:0x6e729
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 000000000000000c 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 5993, tgid 5993 (rm), ts 77942296454, free_ts 77960916066
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0x3651/0x37a0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x292/0x710 mm/page_alloc.c:4739
 alloc_pages_mpol+0x311/0x660 mm/mempolicy.c:2270
 folio_alloc_mpol_noprof mm/mempolicy.c:2289 [inline]
 vma_alloc_folio_noprof+0x12b/0x260 mm/mempolicy.c:2324
 folio_prealloc+0x2e/0x170
 do_cow_fault mm/memory.c:5416 [inline]
 do_fault mm/memory.c:5528 [inline]
 do_pte_missing mm/memory.c:4047 [inline]
 handle_pte_fault mm/memory.c:5889 [inline]
 __handle_mm_fault+0x20bd/0x70f0 mm/memory.c:6032
 handle_mm_fault+0x2c1/0x7e0 mm/memory.c:6201
 do_user_addr_fault arch/x86/mm/fault.c:1338 [inline]
 handle_page_fault arch/x86/mm/fault.c:1481 [inline]
 exc_page_fault+0x459/0x8b0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5993 tgid 5993 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xe2f/0x18a0 mm/page_alloc.c:2707
 folios_put_refs+0x76c/0x860 mm/swap.c:994
 free_pages_and_swap_cache+0x2e5/0x690 mm/swap_state.c:331
 __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:389 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:396
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:488
 exit_mmap+0x52a/0xd40 mm/mmap.c:1297
 __mmput+0x115/0x410 kernel/fork.c:1345
 exit_mm+0x220/0x310 kernel/exit.c:570
 do_exit+0x9ad/0x28e0 kernel/exit.c:925
 do_group_exit+0x207/0x2c0 kernel/exit.c:1087
 __do_sys_exit_group kernel/exit.c:1098 [inline]
 __se_sys_exit_group kernel/exit.c:1096 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1096
 x64_sys_call+0x26a8/0x26b0 arch/x86/include/generated/asm/syscalls_64.h:232
 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:
 ffff88806e728f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806e729000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806e729080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88806e729100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806e729180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================