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BUG: KASAN: slab-use-after-free in rose_timer_expiry+0x471/0x4b0
Read of size 2 at addr ffff888121b4d42a by task syz.2.8127/3796

CPU: 0 UID: 0 PID: 3796 Comm: syz.2.8127 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:_raw_spin_unlock_irq+0x29/0x50
Code: 90 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ea fc 20 f6 48 89 df e8 42 94 21 f6 e8 0d e6 4a f6 fb bf 01 00 00 00 <e8> a2 8e 13 f6 65 8b 05 6b f1 23 07 85 c0 74 07 5b e9 51 4c 00 00
RSP: 0000:ffffc9000775fcc0 EFLAGS: 00000282
RAX: ac57bdb50f65bd00 RBX: ffff8881074c1300 RCX: ac57bdb50f65bd00
RDX: 0000000000000000 RSI: ffffffff8be33660 RDI: 0000000000000001
RBP: 000000000000000b R08: ffffffff8fa38437 R09: 1ffffffff1f47086
R10: dffffc0000000000 R11: fffffbfff1f47087 R12: 1ffff11020e9829b
R13: 0000000000000000 R14: 0000000044000004 R15: ffff8881074c14d8
 get_signal+0x11a8/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 irqentry_exit_to_user_mode+0x81/0x120
 exc_page_fault+0x9f/0xf0
 asm_exc_page_fault+0x26/0x30
RIP: 0033:0x7f60f4e550b3
Code: 8b 44 24 08 48 85 c0 74 17 48 8b 54 24 18 48 0f ca 48 89 54 24 18 48 83 f8 01 0f 85 7a 02 00 00 48 8b 44 24 10 48 8b 54 24 18 <48> 89 10 e9 d2 fd ff ff 48 8b 44 24 10 0f b7 10 48 8b 44 24 08 48
RSP: 002b:00007ffe37030930 EFLAGS: 00010246
RAX: 0000200000000258 RBX: 0000000000000008 RCX: 0000000000000000
RDX: 0000000000000009 RSI: 0000000000000000 RDI: 0000555587f243c8
RBP: 00007ffe37030a38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00007f60f51b5fac
R13: 00007f60f51b5fa0 R14: fffffffffffffffe R15: 0000000000000001
 </TASK>

Allocated by task 3707:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x230/0x3d0
 cfcnfg_create+0x68/0x380
 caif_init_net+0x81/0xc0
 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 5854:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5b/0x80
 kfree+0x18e/0x440
 caif_exit_net+0x480/0x4a0
 ops_undo_list+0x49a/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 ffff888121b4d400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 42 bytes inside of
 freed 512-byte region [ffff888121b4d400, ffff888121b4d600)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121b4c
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff88801a441c80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff88801a441c80 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 057ff00000000002 ffffea000486d301 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 18975, tgid 18974 (syz.0.3434), ts 249997212311, free_ts 249991853929
 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
 device_add+0xbe/0xb50
 netdev_register_kobject+0x178/0x310
 register_netdevice+0x126c/0x1ae0
 register_netdev+0x40/0x60
 ip6gre_init_net+0x291/0x3c0
 ops_init+0x35c/0x5c0
 setup_net+0x10c/0x320
 copy_net_ns+0x31b/0x4d0
 create_new_namespaces+0x3f3/0x720
page last free pid 18975 tgid 18974 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
 __kmalloc_cache_noprof+0x1be/0x3d0
 ref_tracker_alloc+0x133/0x460
 netdev_queue_update_kobjects+0x1d1/0x6c0
 netdev_register_kobject+0x258/0x310
 register_netdevice+0x126c/0x1ae0
 register_netdev+0x40/0x60
 vti6_init_net+0x238/0x370
 ops_init+0x35c/0x5c0
 setup_net+0x10c/0x320
 copy_net_ns+0x31b/0x4d0
 create_new_namespaces+0x3f3/0x720

Memory state around the buggy address:
 ffff888121b4d300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888121b4d380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888121b4d400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff888121b4d480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888121b4d500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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