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BUG: KASAN: slab-out-of-bounds in fib6_add_rt2node+0x369c/0x3bc0 net/ipv6/ip6_fib.c:1142
Read of size 1 at addr ffff8880323ac4de by task syz.9.1403/11983

CPU: 0 UID: 0 PID: 11983 Comm: syz.9.1403 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 lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x156/0x4c9 mm/kasan/report.c:482
 kasan_report+0xdf/0x1a0 mm/kasan/report.c:595
 fib6_add_rt2node+0x369c/0x3bc0 net/ipv6/ip6_fib.c:1142
 fib6_add_rt2node_nh net/ipv6/ip6_fib.c:1363 [inline]
 fib6_add+0x3fe/0x1d20 net/ipv6/ip6_fib.c:1531
 __ip6_ins_rt net/ipv6/route.c:1351 [inline]
 ip6_route_add+0xf9/0x1d0 net/ipv6/route.c:3957
 inet6_rtm_newroute+0x157/0x160 net/ipv6/route.c:5660
 rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa54/0xc30 net/socket.c:2592
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646
 __sys_sendmsg+0x170/0x220 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f362c99aeb9
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:00007f362d842028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f362cc15fa0 RCX: 00007f362c99aeb9
RDX: 0000000000000000 RSI: 0000200000004380 RDI: 0000000000000003
RBP: 00007f362ca08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f362cc16038 R14: 00007f362cc15fa0 R15: 00007fffe3e5dda8
 </TASK>

Allocated by task 10460:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5657 [inline]
 __kmalloc_noprof+0x347/0x9c0 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 fib6_info_alloc+0x40/0x160 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x14c/0xad0 net/ipv6/route.c:3820
 ip6_route_add+0x4b/0x1d0 net/ipv6/route.c:3949
 inet6_rtm_newroute+0x157/0x160 net/ipv6/route.c:5660
 rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa54/0xc30 net/socket.c:2592
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646
 __sys_sendmsg+0x170/0x220 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880323ac400
 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 [ffff8880323ac400, ffff8880323ac4c8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff8880323ace00 pfn:0x323ac
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 ffffea00014dd890 ffffea0000d8e110
raw: ffff8880323ace00 0000000000100003 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe26b40 ffffea00014dd890 ffffea0000d8e110
head: ffff8880323ace00 0000000000100003 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0000c8eb01 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 5812, tgid 5812 (syz-executor), ts 66852777770, free_ts 66675694565
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1e1/0x250 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0xe3d/0x2e10 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x26c/0x2410 mm/page_alloc.c:5240
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab mm/slub.c:3248 [inline]
 new_slab+0x2c4/0x440 mm/slub.c:3302
 ___slab_alloc+0xda3/0x1ca0 mm/slub.c:4656
 __slab_alloc.isra.0+0x63/0x110 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+0x618/0x9c0 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 fib_create_info+0x5bf/0x4640 net/ipv4/fib_semantics.c:1402
 fib_table_insert+0x169/0x1c70 net/ipv4/fib_trie.c:1212
 fib_magic+0x4d4/0x5c0 net/ipv4/fib_frontend.c:1134
 fib_add_ifaddr+0x4ba/0x560 net/ipv4/fib_frontend.c:1178
 fib_netdev_event+0x3d6/0x710 net/ipv4/fib_frontend.c:1516
 notifier_call_chain+0x99/0x3b0 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2243
 call_netdevice_notifiers_extack net/core/dev.c:2281 [inline]
 call_netdevice_notifiers net/core/dev.c:2295 [inline]
 __dev_notify_flags+0x12c/0x2e0 net/core/dev.c:9788
page last free pid 5906 tgid 5906 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0x822/0x1130 mm/page_alloc.c:2973
 discard_slab mm/slub.c:3346 [inline]
 __put_partials+0x127/0x160 mm/slub.c:3886
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xe0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 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_noprof+0x2ad/0x780 mm/slub.c:5270
 getname_flags.part.0+0x4c/0x540 fs/namei.c:146
 getname_flags+0x93/0xf0 include/linux/audit.h:345
 getname include/linux/fs.h:2500 [inline]
 do_sys_openat2+0xc5/0x220 fs/open.c:1426
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880323ac380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880323ac400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880323ac480: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
                                                    ^
 ffff8880323ac500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880323ac580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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