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BUG: KASAN: use-after-free in ip6_forward+0x1799/0x1ae0 net/ipv6/ip6_output.c:533
Read of size 1 at addr ffff88810ba3bc47 by task syz.6.2032/8180

CPU: 0 PID: 8180 Comm: syz.6.2032 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 ip6_forward+0x1799/0x1ae0 net/ipv6/ip6_output.c:533
 dst_input include/net/dst.h:461 [inline]
 ip6_rcv_finish+0x18c/0x360 net/ipv6/ip6_input.c:80
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ipv6_rcv+0xf0/0x230 net/ipv6/ip6_input.c:301
 __netif_receive_skb_one_core net/core/dev.c:5413 [inline]
 __netif_receive_skb+0xc8/0x280 net/core/dev.c:5527
 netif_receive_skb_internal net/core/dev.c:5632 [inline]
 netif_receive_skb+0x9b/0x3e0 net/core/dev.c:5691
 tun_rx_batched+0x600/0x750 drivers/net/tun.c:-1
 tun_get_user+0x26f6/0x31a0 drivers/net/tun.c:2037
 tun_chr_write_iter+0x1c1/0x270 drivers/net/tun.c:2070
 call_write_iter include/linux/fs.h:2072 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_write+0x14a/0x260 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f383ed302d9
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:00007f383d789028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f383efb7fa0 RCX: 00007f383ed302d9
RDX: 0000000000000ffe RSI: 0000200000000100 RDI: 0000000000000003
RBP: 00007f383edc7888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f383efb8038 R14: 00007f383efb7fa0 R15: 00007fff99cf7a68

Allocated by task 0:
(stack is not available)

Freed by task 8180:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 skb_free_head net/core/skbuff.c:606 [inline]
 pskb_expand_head+0x386/0x11c0 net/core/skbuff.c:1691
 __pskb_pull_tail+0xb2/0x1450 net/core/skbuff.c:2197
 pskb_may_pull include/linux/skbuff.h:2397 [inline]
 decode_session6 net/xfrm/xfrm_policy.c:3425 [inline]
 __xfrm_decode_session+0x591/0x2310 net/xfrm/xfrm_policy.c:3524
 __xfrm_policy_check+0x252/0x29d0 net/xfrm/xfrm_policy.c:3579
 __xfrm_policy_check2 include/net/xfrm.h:1117 [inline]
 xfrm_policy_check include/net/xfrm.h:1122 [inline]
 xfrm6_policy_check include/net/xfrm.h:1132 [inline]
 ip6_forward+0xba1/0x1ae0 net/ipv6/ip6_output.c:505
 dst_input include/net/dst.h:461 [inline]
 ip6_rcv_finish+0x18c/0x360 net/ipv6/ip6_input.c:80
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ipv6_rcv+0xf0/0x230 net/ipv6/ip6_input.c:301
 __netif_receive_skb_one_core net/core/dev.c:5413 [inline]
 __netif_receive_skb+0xc8/0x280 net/core/dev.c:5527
 netif_receive_skb_internal net/core/dev.c:5632 [inline]
 netif_receive_skb+0x9b/0x3e0 net/core/dev.c:5691
 tun_rx_batched+0x600/0x750 drivers/net/tun.c:-1
 tun_get_user+0x26f6/0x31a0 drivers/net/tun.c:2037
 tun_chr_write_iter+0x1c1/0x270 drivers/net/tun.c:2070
 call_write_iter include/linux/fs.h:2072 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_write+0x14a/0x260 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810ba3bc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 71 bytes inside of
 512-byte region [ffff88810ba3bc00, ffff88810ba3be00)
The buggy address belongs to the page:
page:ffffea00042e8e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ba38
head:ffffea00042e8e00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
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 280, ts 23631229924, free_ts 23625278205
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc+0x1f9/0x330 mm/slub.c:4034
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 tnode_alloc net/ipv4/fib_trie.c:331 [inline]
 tnode_new net/ipv4/fib_trie.c:384 [inline]
 inflate net/ipv4/fib_trie.c:544 [inline]
 resize+0x2c3/0x24f0 net/ipv4/fib_trie.c:868
 trie_rebalance net/ipv4/fib_trie.c:1059 [inline]
 fib_insert_node net/ipv4/fib_trie.c:1103 [inline]
 fib_insert_alias+0xb4e/0x1070 net/ipv4/fib_trie.c:1117
 fib_table_insert+0x732/0x1d60 net/ipv4/fib_trie.c:1309
 fib_magic net/ipv4/fib_frontend.c:1107 [inline]
 fib_add_ifaddr+0x360/0xf90 net/ipv4/fib_frontend.c:1129
 fib_inetaddr_event+0x15d/0x310 net/ipv4/fib_frontend.c:1445
 notifier_call_chain kernel/notifier.c:83 [inline]
 blocking_notifier_call_chain+0xba/0x140 kernel/notifier.c:337
 __inet_insert_ifa+0x88e/0xa80 net/ipv4/devinet.c:567
 inet_rtm_newaddr+0x8cf/0x1580 net/ipv4/devinet.c:967
 rtnetlink_rcv_msg+0x9e9/0xca0 net/core/rtnetlink.c:5622
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x390 mm/page_alloc.c:5454
 __free_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab mm/slub.c:1920 [inline]
 unfreeze_partials+0x150/0x180 mm/slub.c:2415
 put_cpu_partial+0xc1/0x180 mm/slub.c:2451
 __slab_free+0x2c9/0x3a0 mm/slub.c:3100
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x10e/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965
 sock_alloc_inode+0x1b/0xb0 net/socket.c:253
 alloc_inode fs/inode.c:233 [inline]
 new_inode_pseudo+0x62/0x210 fs/inode.c:968
 sock_alloc net/socket.c:574 [inline]
 __sock_create+0x12c/0x770 net/socket.c:1401

Memory state around the buggy address:
 ffff88810ba3bb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810ba3bb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88810ba3bc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88810ba3bc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810ba3bd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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