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BUG: KASAN: slab-use-after-free in rose_timer_expiry+0x471/0x4b0
Read of size 2 at addr ffff88810c6d882a by task syz.0.4351/20431

CPU: 1 UID: 0 PID: 20431 Comm: syz.0.4351 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:
 <IRQ>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 rose_timer_expiry+0x471/0x4b0
 call_timer_fn+0x17e/0x5f0
 __run_timer_base+0x61a/0x860
 run_timer_softirq+0xb7/0x180
 handle_softirqs+0x286/0x870
 __irq_exit_rcu+0xca/0x1f0
 irq_exit_rcu+0x9/0x30
 sysvec_apic_timer_interrupt+0xa6/0xc0
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20
RIP: 0010:free_pages_and_swap_cache+0x14b/0x520
Code: 89 44 24 10 4c 8d 70 08 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 f7 e8 68 bd 08 00 4d 8b 36 <4c> 89 f6 48 83 e6 01 31 ff e8 e7 58 a5 ff 4c 89 f0 48 83 e0 01 0f
RSP: 0018:ffffc9000267f4c0 EFLAGS: 00000246
RAX: 1ffffd400087f2b9 RBX: ffff8881070bb4c8 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 000000000000001b RDI: 000000000000001f
RBP: ffffc9000267f748 R08: ffffea00041ba7c7 R09: 1ffffd40008374f8
R10: dffffc0000000000 R11: fffff940008374f9 R12: 1ffff11020e17699
R13: ffffea00043f95c0 R14: 0000000000000000 R15: 0000000000000097
 tlb_flush_mmu+0x3a0/0x680
 tlb_finish_mmu+0xc3/0x1d0
 exit_mmap+0x44c/0xb50
 __mmput+0x118/0x420
 exit_mm+0x1da/0x2c0
 do_exit+0x648/0x2300
 do_group_exit+0x21c/0x2d0
 get_signal+0x1286/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 exit_to_user_mode_loop+0x75/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc81858ebe9
Code: Unable to access opcode bytes at 0x7fc81858ebbf.
RSP: 002b:00007fc8193e80e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007fc8187b5fa8 RCX: 00007fc81858ebe9
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fc8187b5fac
RBP: 00007fc8187b5fa0 R08: 7fffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc8187b6038 R14: 00007ffe875486a0 R15: 00007ffe87548788
 </TASK>

Allocated by task 19832:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x230/0x3d0
 device_add+0xbe/0xb50
 netdev_register_kobject+0x178/0x310
 register_netdevice+0x126c/0x1ae0
 register_netdev+0x40/0x60
 sit_init_net+0x228/0x5c0
 ops_init+0x35c/0x5c0
 setup_net+0x10c/0x320
 copy_net_ns+0x31b/0x4d0
 create_new_namespaces+0x3f3/0x720
 unshare_nsproxy_namespaces+0x11c/0x170
 ksys_unshare+0x4c8/0x8c0
 __x64_sys_unshare+0x38/0x50
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5871:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5b/0x80
 kfree+0x18e/0x440
 kobject_put+0x22b/0x480
 netdev_run_todo+0xd2e/0xea0
 ops_undo_list+0x3e1/0x990
 cleanup_net+0x4c5/0x800
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30

The buggy address belongs to the object at ffff88810c6d8800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 42 bytes inside of
 freed 512-byte region [ffff88810c6d8800, ffff88810c6d8a00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88810c6d8400 pfn:0x10c6d8
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000240(workingset|head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000240 ffff88801a441c80 ffffea000453aa10 ffffea000466bb10
raw: ffff88810c6d8400 0000000000100003 00000000f5000000 0000000000000000
head: 057ff00000000240 ffff88801a441c80 ffffea000453aa10 ffffea000466bb10
head: ffff88810c6d8400 0000000000100003 00000000f5000000 0000000000000000
head: 057ff00000000002 ffffea000431b601 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 12, tgid 12 (kworker/u8:0), ts 48809762778, free_ts 48663572806
 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_cache_noprof+0x296/0x3d0
 __ipv6_dev_mc_inc+0x44f/0xa50
 addrconf_dad_work+0x3d0/0x14b0
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
page last free pid 5850 tgid 5850 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __put_partials+0x156/0x1a0
 put_cpu_partial+0x17c/0x250
 __slab_free+0x2d5/0x3c0
 qlist_free_all+0x97/0x140
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 kmem_cache_alloc_node_noprof+0x1bb/0x3c0
 __alloc_skb+0x112/0x2d0
 netlink_sendmsg+0x5c6/0xb30
 __sock_sendmsg+0x21c/0x270
 __sys_sendto+0x3bd/0x520
 __x64_sys_sendto+0xde/0x100
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88810c6d8700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810c6d8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88810c6d8800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88810c6d8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810c6d8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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