IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE
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BUG: KASAN: slab-out-of-bounds in skb_headlen include/linux/skbuff.h:1914 [inline]
BUG: KASAN: slab-out-of-bounds in pskb_may_pull include/linux/skbuff.h:2128 [inline]
BUG: KASAN: slab-out-of-bounds in skb_ensure_writable+0x28a/0x2e0 net/core/skbuff.c:5024
Read of size 4 at addr ffff8881c81d60f8 by task syz-executor4/25266

CPU: 1 PID: 25266 Comm: syz-executor4 Not tainted 4.14.93+ #6
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 print_address_description+0x60/0x226 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0x88/0x2a5 mm/kasan/report.c:393

Allocated by task 190:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc.part.0+0x4f/0xd0 mm/kasan/kasan.c:551
 slab_post_alloc_hook mm/slab.h:442 [inline]
 slab_alloc_node mm/slub.c:2723 [inline]
 slab_alloc mm/slub.c:2731 [inline]
 kmem_cache_alloc+0xd2/0x2d0 mm/slub.c:2736
 kmem_cache_alloc_node include/linux/slab.h:361 [inline]
 __alloc_skb+0xd7/0x550 net/core/skbuff.c:193
 alloc_skb include/linux/skbuff.h:980 [inline]
 kobject_uevent_env+0x571/0xc60 lib/kobject_uevent.c:476

Freed by task 190:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:524
 slab_free_hook mm/slub.c:1389 [inline]
 slab_free_freelist_hook mm/slub.c:1410 [inline]
 slab_free mm/slub.c:2966 [inline]
 kmem_cache_free+0xc4/0x330 mm/slub.c:2988
 kfree_skbmem net/core/skbuff.c:582 [inline]
 kfree_skbmem+0xa0/0x100 net/core/skbuff.c:576
 __kfree_skb net/core/skbuff.c:642 [inline]
 consume_skb+0xc6/0x340 net/core/skbuff.c:701
 netlink_broadcast_filtered+0x2b3/0x9d0 net/netlink/af_netlink.c:1488
 kobject_uevent_env+0x6ba/0xc60 lib/kobject_uevent.c:492

The buggy address belongs to the object at ffff8881c81d6000
 which belongs to the cache skbuff_head_cache of size 224
The buggy address is located 24 bytes to the right of
 224-byte region [ffff8881c81d6000, ffff8881c81d60e0)
The buggy address belongs to the page:
page:ffffea0007207580 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000100(slab)
raw: 4000000000000100 0000000000000000 0000000000000000 00000001800c000c
raw: dead000000000100 dead000000000200 ffff8881d6758200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c81d5f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881c81d6000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881c81d6080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                                                ^
 ffff8881c81d6100: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8881c81d6180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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