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BUG: KASAN: use-after-free in kvm_xen_shared_info_init+0x3b7/0x420 arch/x86/kvm/xen.c:91
Read of size 4 at addr ffff88806a7f5900 by task syz.1.2708/15088

CPU: 0 UID: 0 PID: 15088 Comm: syz.1.2708 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 kvm_xen_shared_info_init+0x3b7/0x420 arch/x86/kvm/xen.c:91
 kvm_xen_hvm_set_attr+0xcef/0x16a0 arch/x86/kvm/xen.c:821
 kvm_arch_vm_ioctl+0x2a0/0x18d0 arch/x86/kvm/x86.c:4630
 kvm_vm_ioctl+0x167d/0x42d0 virt/kvm/kvm_main.c:5400
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f43c459e159
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:00007f43c54ca028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f43c4826360 RCX: 00007f43c459e159
RDX: 0000200000000840 RSI: 000000004048aec9 RDI: 0000000000000005
RBP: 00007f43c4635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f43c48263f8 R14: 00007f43c4826360 R15: 00007ffc5f786978
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xe pfn:0x6a7f5
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00012c8b88 ffff8880b8441b70 0000000000000000
raw: 000000000000000e 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_ZERO|__GFP_COMP), pid 15088, tgid 15079 (syz.1.2708), ts 881652084370
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35d0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 alloc_pages_mpol+0x201/0x550 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof+0x36/0x260 mm/mempolicy.c:2505
 vma_alloc_folio_noprof+0xed/0x1d0 mm/mempolicy.c:2540
 folio_prealloc mm/memory.c:1289 [inline]
 alloc_anon_folio mm/memory.c:5387 [inline]
 do_anonymous_page+0xac9/0x2050 mm/memory.c:5482
 do_pte_missing mm/memory.c:4698 [inline]
 handle_pte_fault mm/memory.c:6558 [inline]
 __handle_mm_fault+0x1ff3/0x2f60 mm/memory.c:6707
 handle_mm_fault+0x363/0xa20 mm/memory.c:6876
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0x8ae/0x2c30 mm/gup.c:1428
 __get_user_pages_locked mm/gup.c:1692 [inline]
 get_user_pages_unlocked+0x1cb/0x7d0 mm/gup.c:2676
 hva_to_pfn_slow virt/kvm/kvm_main.c:2904 [inline]
 hva_to_pfn+0x871/0xd60 virt/kvm/kvm_main.c:3000
 hva_to_pfn_retry virt/kvm/pfncache.c:209 [inline]
 __kvm_gpc_refresh+0xc24/0x22d0 virt/kvm/pfncache.c:330
 __kvm_gpc_activate+0x2ab/0x490 virt/kvm/pfncache.c:424
 kvm_gpc_activate_hva+0x73/0xa0 virt/kvm/pfncache.c:444
 kvm_xen_hvm_set_attr+0x395/0x16a0 arch/x86/kvm/xen.c:813
page last free pid 15088 tgid 15079 ts 882444286267 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x79f/0x10f0 mm/page_alloc.c:2962
 __folio_put+0x3b4/0x5f0 mm/folio.c:105
 folio_put include/linux/mm.h:2160 [inline]
 put_page include/linux/mm.h:2229 [inline]
 kvm_release_page_clean virt/kvm/kvm_main.c:2814 [inline]
 kvm_release_page_clean+0x1dc/0x250 virt/kvm/kvm_main.c:2808
 hva_to_pfn_retry virt/kvm/pfncache.c:246 [inline]
 __kvm_gpc_refresh+0x1a69/0x22d0 virt/kvm/pfncache.c:330
 __kvm_gpc_activate+0x2ab/0x490 virt/kvm/pfncache.c:424
 kvm_gpc_activate_hva+0x73/0xa0 virt/kvm/pfncache.c:444
 kvm_xen_hvm_set_attr+0x395/0x16a0 arch/x86/kvm/xen.c:813
 kvm_arch_vm_ioctl+0x2a0/0x18d0 arch/x86/kvm/x86.c:4630
 kvm_vm_ioctl+0x167d/0x42d0 virt/kvm/kvm_main.c:5400
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88806a7f5800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806a7f5880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806a7f5900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88806a7f5980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806a7f5a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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