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BUG: KASAN: slab-use-after-free in kvm_gmem_release+0x155/0x380
Write of size 8 at addr ffff888020450d08 by task syz.1.24660/18648

CPU: 0 UID: 0 PID: 18648 Comm: syz.1.24660 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 kvm_gmem_release+0x155/0x380
 __fput+0x44c/0xa70
 task_work_run+0x1d4/0x260
 exit_to_user_mode_loop+0xec/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f834038ebe9
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:00007fffebd9f5d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 000000000026e844 RCX: 00007f834038ebe9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f83405c7da0 R08: 0000000000000001 R09: 0000000aebd9f8cf
R10: 0000001b30b20000 R11: 0000000000000246 R12: 00007f83405c5fac
R13: 00007f83405c5fa0 R14: ffffffffffffffff R15: 00007fffebd9f6f0
 </TASK>

Allocated by task 18649:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x230/0x3d0
 kvm_set_memory_region+0x747/0xb90
 kvm_vm_ioctl_set_memory_region+0x6f/0xd0
 kvm_vm_ioctl+0x957/0xc60
 __se_sys_ioctl+0xf9/0x170
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 18649:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5b/0x80
 kfree+0x18e/0x440
 kvm_set_memslot+0xf77/0x1310
 kvm_set_memory_region+0x966/0xb90
 kvm_vm_ioctl_set_memory_region+0x6f/0xd0
 kvm_vm_ioctl+0x957/0xc60
 __se_sys_ioctl+0xf9/0x170
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888020450c00
 which belongs to the cache kmalloc-cg-512 of size 512
The buggy address is located 264 bytes inside of
 freed 512-byte region [ffff888020450c00, ffff888020450e00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x20450
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880228d6001
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a44b140 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080100010 00000000f5000000 ffff8880228d6001
head: 00fff00000000040 ffff88801a44b140 0000000000000000 dead000000000001
head: 0000000000000000 0000000080100010 00000000f5000000 ffff8880228d6001
head: 00fff00000000002 ffffea0000811401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5583, tgid 5583 (dhcpcd), ts 40391302556, free_ts 39025693661
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x370
 ___slab_alloc+0xbeb/0x1410
 __kmalloc_node_track_caller_noprof+0x2f8/0x4e0
 kmalloc_reserve+0x136/0x290
 __alloc_skb+0x142/0x2d0
 alloc_skb_with_frags+0xca/0x890
 sock_alloc_send_pskb+0x857/0x990
 unix_dgram_sendmsg+0x461/0x1850
 __sock_sendmsg+0x21c/0x270
 sock_write_iter+0x258/0x330
 do_iter_readv_writev+0x619/0x8b0
 vfs_writev+0x31a/0x960
page last free pid 5656 tgid 5656 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __slab_free+0x303/0x3c0
 qlist_free_all+0x97/0x140
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 kmem_cache_alloc_lru_noprof+0x1c6/0x3d0
 __d_alloc+0x36/0x7a0
 d_alloc_parallel+0xe5/0x15e0
 __lookup_slow+0x116/0x3d0
 lookup_slow+0x53/0x70
 link_path_walk+0x935/0xea0
 path_lookupat+0x97/0x430
 filename_lookup+0x212/0x570
 kern_path+0x35/0x50
 unix_find_other+0x183/0xb40
 unix_stream_connect+0x429/0x1010

Memory state around the buggy address:
 ffff888020450c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888020450c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888020450d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff888020450d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888020450e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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