[syzbot] [kvm?] [kvm-x86?] KASAN: use-after-free Read in kvm_xen_shared_info_init

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4d3a2a466b8d HID: core: Fix size_t specifier in hid_report..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1073cd6a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d0f0911eedbc130a
dashboard link: https://syzkaller.appspot.com/bug?extid=0948c82180d475ad24e2
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/03f143994ada/disk-4d3a2a46.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/de287d829354/vmlinux-4d3a2a46.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3467e0106c40/bzImage-4d3a2a46.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0948c8...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in kvm_xen_shared_info_init+0x3c6/0x440 arch/x86/kvm/xen.c:90
Read of size 4 at addr ffff8880517e3900 by task syz.2.1046/11260

CPU: 0 UID: 0 PID: 11260 Comm: syz.2.1046 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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/0x1d0 mm/kasan/report.c:595
kvm_xen_shared_info_init+0x3c6/0x440 arch/x86/kvm/xen.c:90
kvm_xen_hvm_set_attr+0xcef/0x16a0 arch/x86/kvm/xen.c:806
kvm_arch_vm_ioctl+0x2a0/0x18d0 arch/x86/kvm/x86.c:7528
kvm_vm_ioctl+0x1564/0x4050 virt/kvm/kvm_main.c:5380
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:63 [inline]
do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f62be79ce59
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:00007f62bf733028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f62bea15fa0 RCX: 00007f62be79ce59
RDX: 0000000000000004 RSI: 000000004048aec9 RDI: 0000000000000003
RBP: 00007f62be832d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f62bea16038 R14: 00007f62bea15fa0 R15: 00007ffcbacd7668
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x4 pfn:0x517e3
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001595b88 ffff8880b84412f0 0000000000000000
raw: 0000000000000004 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 11260, tgid 11259 (syz.2.1046), ts 375671463264, free_ts 375831741570
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
alloc_pages_mpol+0x1fb/0x540 mm/mempolicy.c:2490
folio_alloc_mpol_noprof+0x36/0x260 mm/mempolicy.c:2509
vma_alloc_folio_noprof+0xed/0x1d0 mm/mempolicy.c:2544
folio_prealloc mm/memory.c:1193 [inline]
wp_page_copy mm/memory.c:3859 [inline]
do_wp_page+0x1ee1/0x4350 mm/memory.c:4320
handle_pte_fault mm/memory.c:6427 [inline]
__handle_mm_fault+0x1ab6/0x2a00 mm/memory.c:6549
handle_mm_fault+0x36d/0xa20 mm/memory.c:6718
faultin_page mm/gup.c:1126 [inline]
__get_user_pages+0x1178/0x32a0 mm/gup.c:1428
__get_user_pages_locked mm/gup.c:1692 [inline]
get_user_pages_unlocked+0x1cb/0x7d0 mm/gup.c:2681
hva_to_pfn_slow virt/kvm/kvm_main.c:2903 [inline]
hva_to_pfn+0x871/0xd60 virt/kvm/kvm_main.c:2999
hva_to_pfn_retry virt/kvm/pfncache.c:209 [inline]
__kvm_gpc_refresh+0xcea/0x22c0 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:798
page last free pid 11260 tgid 11259 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1402 [inline]
__free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
__folio_put+0x3b4/0x5f0 mm/swap.c:112
folio_put include/linux/mm.h:2090 [inline]
put_page include/linux/mm.h:2159 [inline]
kvm_release_page_clean virt/kvm/kvm_main.c:2813 [inline]
kvm_release_page_clean+0x1dc/0x250 virt/kvm/kvm_main.c:2807
hva_to_pfn_retry virt/kvm/pfncache.c:246 [inline]
__kvm_gpc_refresh+0x195d/0x22c0 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:798
kvm_arch_vm_ioctl+0x2a0/0x18d0 arch/x86/kvm/x86.c:7528
kvm_vm_ioctl+0x1564/0x4050 virt/kvm/kvm_main.c:5380
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:63 [inline]
do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff8880517e3800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880517e3880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880517e3900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8880517e3980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880517e3a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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