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BUG: KASAN: use-after-free in nexthop_flush_dev+0x20b/0x230 net/ipv4/nexthop.c:2381
Read of size 8 at addr ffff888147a3f058 by task syz-executor.3/3633

CPU: 1 PID: 3633 Comm: syz-executor.3 Not tainted 5.18.0-syzkaller-04999-g0a375c822497 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
 print_report mm/kasan/report.c:429 [inline]
 kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
 nexthop_flush_dev+0x20b/0x230 net/ipv4/nexthop.c:2381
 nh_netdev_event+0x2c6/0x370 net/ipv4/nexthop.c:3574
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:84
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1943
 call_netdevice_notifiers_extack net/core/dev.c:1981 [inline]
 call_netdevice_notifiers net/core/dev.c:1995 [inline]
 netdev_wait_allrefs_any net/core/dev.c:10225 [inline]
 netdev_run_todo+0xb90/0x10b0 net/core/dev.c:10337
 tun_detach drivers/net/tun.c:695 [inline]
 tun_chr_close+0xe0/0x180 drivers/net/tun.c:3444
 __fput+0x277/0x9d0 fs/file_table.c:317
 task_work_run+0xdd/0x1a0 kernel/task_work.c:177
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0xaff/0x2a00 kernel/exit.c:795
 do_group_exit+0xd2/0x2f0 kernel/exit.c:925
 __do_sys_exit_group kernel/exit.c:936 [inline]
 __se_sys_exit_group kernel/exit.c:934 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:934
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7fc769489109
Code: Unable to access opcode bytes at RIP 0x7fc7694890df.
RSP: 002b:00007fff5d0435b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fff5d043c30 RCX: 00007fc769489109
RDX: 00007fc769488217 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 0000000000000007 R08: 0000000000000005 R09: 00007fff5d043c30
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000032
R13: 000000000006e58e R14: 0000000000000005 R15: 00007fff5d043c70
 </TASK>

Allocated by task 3633:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:436 [inline]
 ____kasan_kmalloc mm/kasan/common.c:515 [inline]
 ____kasan_kmalloc mm/kasan/common.c:474 [inline]
 __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:524
 kmalloc include/linux/slab.h:588 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 nexthop_net_init+0x71/0x140 net/ipv4/nexthop.c:3753
 ops_init+0xaf/0x470 net/core/net_namespace.c:134
 setup_net+0x5d1/0xc50 net/core/net_namespace.c:325
 copy_net_ns+0x318/0x760 net/core/net_namespace.c:471
 create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
 ksys_unshare+0x445/0x920 kernel/fork.c:3137
 __do_sys_unshare kernel/fork.c:3208 [inline]
 __se_sys_unshare kernel/fork.c:3206 [inline]
 __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3206
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Freed by task 8:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track+0x21/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1727 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
 slab_free mm/slub.c:3507 [inline]
 kfree+0xd6/0x4d0 mm/slub.c:4555
 nexthop_net_exit_batch+0x245/0x2d0 net/ipv4/nexthop.c:3743
 ops_exit_list+0x125/0x170 net/core/net_namespace.c:167
 cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:594
 process_one_work+0x996/0x1610 kernel/workqueue.c:2289
 worker_thread+0x665/0x1080 kernel/workqueue.c:2436
 kthread+0x2e9/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302

The buggy address belongs to the object at ffff888147a3f000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 88 bytes inside of
 2048-byte region [ffff888147a3f000, ffff888147a3f800)

The buggy address belongs to the physical page:
page:ffffea00051e8e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x147a38
head:ffffea00051e8e00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x57ff00000010200(slab|head|node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000010200 ffffea0005146e00 dead000000000002 ffff888010c42000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 7838207039, free_ts 0
 prep_new_page mm/page_alloc.c:2441 [inline]
 get_page_from_freelist+0xba2/0x3e00 mm/page_alloc.c:4182
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5408
 alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2104
 alloc_pages+0x2b1/0x310 mm/mempolicy.c:2267
 alloc_slab_page mm/slub.c:1797 [inline]
 allocate_slab+0x26c/0x3c0 mm/slub.c:1942
 new_slab mm/slub.c:2002 [inline]
 ___slab_alloc+0x985/0xd90 mm/slub.c:3002
 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3089
 slab_alloc_node mm/slub.c:3180 [inline]
 slab_alloc mm/slub.c:3222 [inline]
 kmem_cache_alloc_trace+0x310/0x3f0 mm/slub.c:3253
 kmalloc include/linux/slab.h:588 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 device_create_groups_vargs+0x8a/0x280 drivers/base/core.c:4044
 device_create+0xdf/0x120 drivers/base/core.c:4104
 bdi_register_va.part.0+0x9c/0x800 mm/backing-dev.c:880
 bdi_register_va mm/backing-dev.c:915 [inline]
 bdi_register+0x12a/0x140 mm/backing-dev.c:912
 device_add_disk+0x83c/0xe20 block/genhd.c:511
 add_disk include/linux/blkdev.h:761 [inline]
 loop_add+0x8b8/0xb00 drivers/block/loop.c:2031
 loop_init+0x1f4/0x216 drivers/block/loop.c:2233
 do_one_initcall+0x103/0x650 init/main.c:1295
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888147a3ef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888147a3ef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888147a3f000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff888147a3f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888147a3f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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