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BUG: KASAN: slab-out-of-bounds in fib6_add_rt2node+0x349c/0x3500 net/ipv6/ip6_fib.c:1142
Read of size 1 at addr ffff888078b032de by task syz.7.947/10870

CPU: 0 UID: 0 PID: 10870 Comm: syz.7.947 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 fib6_add_rt2node+0x349c/0x3500 net/ipv6/ip6_fib.c:1142
 fib6_add_rt2node_nh net/ipv6/ip6_fib.c:1363 [inline]
 fib6_add+0x910/0x18c0 net/ipv6/ip6_fib.c:1531
 __ip6_ins_rt net/ipv6/route.c:1351 [inline]
 ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3957
 inet6_rtm_newroute+0x268/0x19e0 net/ipv6/route.c:5660
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa8c479aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa8c5743028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fa8c4a15fa0 RCX: 00007fa8c479aeb9
RDX: 0000000000000000 RSI: 0000200000000080 RDI: 0000000000000004
RBP: 00007fa8c4808c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa8c4a16038 R14: 00007fa8c4a15fa0 R15: 00007ffdbff26588
 </TASK>

Allocated by task 9643:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5657 [inline]
 __kmalloc_noprof+0x40c/0x7e0 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 fib6_info_alloc+0x30/0xf0 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x142/0x860 net/ipv6/route.c:3820
 ip6_route_add+0x49/0x1b0 net/ipv6/route.c:3949
 inet6_rtm_newroute+0x268/0x19e0 net/ipv6/route.c:5660
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888078b03200
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 22 bytes to the right of
 allocated 200-byte region [ffff888078b03200, ffff888078b032c8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888078b02e00 pfn:0x78b02
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fe26b40 ffffea0001d31390 ffffea0001dfac90
raw: ffff888078b02e00 000000000010000f 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe26b40 ffffea0001d31390 ffffea0001dfac90
head: ffff888078b02e00 000000000010000f 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0001e2c081 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5841, tgid 5841 (syz-executor), ts 101171102352, free_ts 101146947253
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3a0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xd82/0x1760 mm/slub.c:4656
 __slab_alloc+0x65/0x100 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kmalloc_noprof+0x46c/0x7e0 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 fib_create_info+0x171d/0x31f0 net/ipv4/fib_semantics.c:1402
 fib_table_insert+0xc8/0x1b50 net/ipv4/fib_trie.c:1212
 fib_magic+0x434/0x510 net/ipv4/fib_frontend.c:1134
 fib_add_ifaddr+0x38d/0x5f0 net/ipv4/fib_frontend.c:1171
 fib_netdev_event+0x382/0x490 net/ipv4/fib_frontend.c:1516
 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2281 [inline]
 call_netdevice_notifiers net/core/dev.c:2295 [inline]
 __dev_notify_flags+0x1a9/0x310 net/core/dev.c:9788
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9817
page last free pid 5977 tgid 5975 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xbf8/0xd70 mm/page_alloc.c:2973
 __slab_free+0x2ce/0x320 mm/slub.c:6008
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_node_noprof+0x427/0x6f0 mm/slub.c:5315
 __alloc_skb+0x1d7/0x390 net/core/skbuff.c:679
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 rtmsg_ifinfo_build_skb+0x84/0x260 net/core/rtnetlink.c:4407
 rtmsg_ifinfo_event net/core/rtnetlink.c:4449 [inline]
 rtmsg_ifinfo+0x8c/0x1a0 net/core/rtnetlink.c:4458
 netif_state_change+0x297/0x3a0 net/core/dev.c:1599
 do_setlink+0xbf6/0x4590 net/core/rtnetlink.c:3405
 rtnl_group_changelink net/core/rtnetlink.c:3790 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3944 [inline]
 rtnl_newlink+0x147a/0x1be0 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894

Memory state around the buggy address:
 ffff888078b03180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888078b03200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888078b03280: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
                                                    ^
 ffff888078b03300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888078b03380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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