=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
include/linux/kvm_host.h:889 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.4.281/5307:
 #0: ffff88805dcac0c8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x1c8/0xb80 virt/kvm/kvm_main.c:3871

stack backtrace:
CPU: 1 PID: 5307 Comm: syz.4.281 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 __kvm_memslots include/linux/kvm_host.h:887 [inline]
 kvm_vcpu_memslots+0x1b6/0x200 include/linux/kvm_host.h:901
 kvm_vcpu_gfn_to_memslot+0x2b/0x3c0 virt/kvm/kvm_main.c:2158
 kvm_vcpu_unmap+0x5b/0x80 virt/kvm/kvm_main.c:2773
 free_nested+0x3cf/0x680 arch/x86/kvm/vmx/nested.c:311
 kvm_leave_nested arch/x86/kvm/x86.c:618 [inline]
 kvm_vcpu_ioctl_x86_set_vcpu_events+0x95b/0x1190 arch/x86/kvm/x86.c:4812
 kvm_arch_vcpu_ioctl+0x1092/0x19d0 arch/x86/kvm/x86.c:5297
 kvm_vcpu_ioctl+0x6b1/0xb80 virt/kvm/kvm_main.c:4050
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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: 0033:0x7f64152416c9
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:00007f6413487038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6415498090 RCX: 00007f64152416c9
RDX: 0000200000000180 RSI: 000000004040aea0 RDI: 0000000000000005
RBP: 00007f64152c3f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6415498128 R14: 00007f6415498090 R15: 00007fff4cf83a18
 </TASK>
==================================================================
BUG: KASAN: use-after-free in try_get_memslot include/linux/kvm_host.h:1323 [inline]
BUG: KASAN: use-after-free in kvm_vcpu_gfn_to_memslot+0x395/0x3c0 virt/kvm/kvm_main.c:2162
Read of size 4 at addr ffff88806183000c by task syz.4.281/5307

CPU: 0 PID: 5307 Comm: syz.4.281 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 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
 try_get_memslot include/linux/kvm_host.h:1323 [inline]
 kvm_vcpu_gfn_to_memslot+0x395/0x3c0 virt/kvm/kvm_main.c:2162
 kvm_vcpu_unmap+0x5b/0x80 virt/kvm/kvm_main.c:2773
 free_nested+0x3cf/0x680 arch/x86/kvm/vmx/nested.c:311
 kvm_leave_nested arch/x86/kvm/x86.c:618 [inline]
 kvm_vcpu_ioctl_x86_set_vcpu_events+0x95b/0x1190 arch/x86/kvm/x86.c:4812
 kvm_arch_vcpu_ioctl+0x1092/0x19d0 arch/x86/kvm/x86.c:5297
 kvm_vcpu_ioctl+0x6b1/0xb80 virt/kvm/kvm_main.c:4050
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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: 0033:0x7f64152416c9
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:00007f6413487038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6415498090 RCX: 00007f64152416c9
RDX: 0000200000000180 RSI: 000000004040aea0 RDI: 0000000000000005
RBP: 00007f64152c3f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6415498128 R14: 00007f6415498090 R15: 00007fff4cf83a18
 </TASK>

The buggy address belongs to the page:
page:ffffea0001860c00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x61830
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 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 5, migratetype Unmovable, gfp_mask 0x552dc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO|__GFP_ACCOUNT), pid 5302, ts 153429914160, free_ts 153453107797
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
 __alloc_pages_node include/linux/gfp.h:570 [inline]
 alloc_pages_node include/linux/gfp.h:584 [inline]
 kmalloc_large_node+0x7d/0x190 mm/slub.c:4426
 __kmalloc_node+0x232/0x3b0 mm/slub.c:4442
 kmalloc_node include/linux/slab.h:630 [inline]
 kvmalloc_node+0x84/0x130 mm/util.c:619
 kvmalloc include/linux/mm.h:816 [inline]
 kvzalloc include/linux/mm.h:824 [inline]
 kvm_dup_memslots virt/kvm/kvm_main.c:1588 [inline]
 kvm_set_memslot+0x195/0x19c0 virt/kvm/kvm_main.c:1620
 __kvm_set_memory_region+0xaf6/0xd40 virt/kvm/kvm_main.c:1843
 kvm_set_memory_region virt/kvm/kvm_main.c:1864 [inline]
 kvm_vm_ioctl_set_memory_region+0x6f/0xa0 virt/kvm/kvm_main.c:1876
 kvm_vm_ioctl+0x8c4/0xa80 virt/kvm/kvm_main.c:4493
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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_pages_ok+0x89f/0x940 mm/page_alloc.c:1643
 free_nonslab_page+0xe2/0x150 mm/slub.c:3540
 kvm_set_memslot+0x1316/0x19c0 virt/kvm/kvm_main.c:1696
 __kvm_set_memory_region+0xaf6/0xd40 virt/kvm/kvm_main.c:1843
 kvm_set_memory_region virt/kvm/kvm_main.c:1864 [inline]
 kvm_vm_ioctl_set_memory_region+0x6f/0xa0 virt/kvm/kvm_main.c:1876
 kvm_vm_ioctl+0x8c4/0xa80 virt/kvm/kvm_main.c:4493
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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

Memory state around the buggy address:
 ffff88806182ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806182ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888061830000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff888061830080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888061830100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================