KASAN: use-after-free Read in __ipv6_addr_type

Status: upstream: reported C repro on 2026/11/14 22:20
Reported-by: syzbot+1f8dd40540b457df7f18@syzkaller.appspotmail.com
First crash: 9h49m, last: 9h49m
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: use-after-free Read in __ipv6_addr_type origin:lts 19 syz, C 6 31d 59d 0/2 upstream: reported C repro on 2026/09/16 12:02
android-5-10 KASAN: use-after-free Read in __ipv6_addr_type 19 syz, C 1 26d 41d 0/2 upstream: reported C repro on 2026/10/04 22:38
upstream KASAN: use-after-free Read in __ipv6_addr_type net 19 1 2885d 2885d 11/29 fixed on 2019/01/11 01:22
upstream KMSAN: kernel-infoleak in copyout (2) net 17 syz, C 6723 1256d 2424d 22/29 fixed on 2023/06/08 14:41
upstream KMSAN: uninit-value in __ipv6_addr_type net 7 syz, C 3 632d 632d 28/29 fixed on 2025/06/10 16:19
upstream KMSAN: kernel-infoleak in _copy_to_iter (7) net 21 syz, C 138977 1359d 1712d 22/29 fixed on 2023/02/24 13:50
upstream KMSAN: uninit-value in IP6_ECN_decapsulate net 7 syz, C 981 1061d 2977d 25/29 fixed on 2023/12/21 03:45

Sample crash report:
request_module fs-gadgetfs succeeded, but still no fs?
==================================================================
BUG: KASAN: use-after-free in __ipv6_addr_type+0x272/0x2f0 net/ipv6/addrconf_core.c:42
Read of size 4 at addr ffff888123972048 by task syz-executor366/306

CPU: 1 PID: 306 Comm: syz-executor366 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 __ipv6_addr_type+0x272/0x2f0 net/ipv6/addrconf_core.c:42
 ipv6_addr_type include/net/ipv6.h:519 [inline]
 ip6_forward+0xdf2/0x1c00 net/ipv6/ip6_output.c:630
 dst_input include/net/dst.h:463 [inline]
 ip6_rcv_finish+0x19e/0x370 net/ipv6/ip6_input.c:79
 NF_HOOK include/linux/netfilter.h:305 [inline]
 ipv6_rcv+0xed/0x230 net/ipv6/ip6_input.c:310
 __netif_receive_skb_one_core net/core/dev.c:5636 [inline]
 __netif_receive_skb+0xd7/0x2a0 net/core/dev.c:5750
 netif_receive_skb_internal net/core/dev.c:5836 [inline]
 netif_receive_skb+0x98/0x3e0 net/core/dev.c:5895
 tun_rx_batched+0x1cb/0x7b0 drivers/net/tun.c:1548
 tun_get_user+0x2456/0x32f0 drivers/net/tun.c:1998
 tun_chr_write_iter+0x1f9/0x300 drivers/net/tun.c:2044
 call_write_iter include/linux/fs.h:2282 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ef/0xd00 fs/read_write.c:584
 ksys_write+0x14a/0x260 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:646
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f770f682eb9
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdbcc9ac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f770f6f5448 RCX: 00007f770f682eb9
RDX: 000000000000ffdd RSI: 0000200000000000 RDI: 0000000000000005
RBP: 00007f770f6f5463 R08: 00000000ffffffff R09: 00000000ffffffff
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007f770f6f5333
R13: 00000000ffffffff R14: 0000000000000001 R15: 0000000000000003
 </TASK>

Allocated by task 306:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:380 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 __do_kmalloc_node mm/slab_common.c:938 [inline]
 __kmalloc_node_track_caller+0xb1/0x1e0 mm/slab_common.c:958
 kmalloc_reserve net/core/skbuff.c:449 [inline]
 __alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
 alloc_skb include/linux/skbuff.h:1322 [inline]
 alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6189
 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2770
 tun_alloc_skb drivers/net/tun.c:1524 [inline]
 tun_get_user+0x9c0/0x32f0 drivers/net/tun.c:1842
 tun_chr_write_iter+0x1f9/0x300 drivers/net/tun.c:2044
 call_write_iter include/linux/fs.h:2282 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ef/0xd00 fs/read_write.c:584
 ksys_write+0x14a/0x260 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:646
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 306:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1750 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
 slab_free mm/slub.c:3712 [inline]
 __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728
 kfree+0x6f/0xf0 mm/slab_common.c:990
 skb_free_head net/core/skbuff.c:765 [inline]
 pskb_expand_head+0x436/0x12b0 net/core/skbuff.c:1884
 __pskb_pull_tail+0xae/0x1570 net/core/skbuff.c:2399
 pskb_may_pull_reason include/linux/skbuff.h:2701 [inline]
 pskb_may_pull include/linux/skbuff.h:2709 [inline]
 decode_session6 net/xfrm/xfrm_policy.c:3421 [inline]
 __xfrm_decode_session+0x5d9/0x1e70 net/xfrm/xfrm_policy.c:3514
 xfrm_decode_session include/net/xfrm.h:1178 [inline]
 __xfrm_route_forward+0x116/0x500 net/xfrm/xfrm_policy.c:3725
 xfrm_route_forward include/net/xfrm.h:1199 [inline]
 xfrm6_route_forward include/net/xfrm.h:1209 [inline]
 ip6_forward+0xce5/0x1c00 net/ipv6/ip6_output.c:592
 dst_input include/net/dst.h:463 [inline]
 ip6_rcv_finish+0x19e/0x370 net/ipv6/ip6_input.c:79
 NF_HOOK include/linux/netfilter.h:305 [inline]
 ipv6_rcv+0xed/0x230 net/ipv6/ip6_input.c:310
 __netif_receive_skb_one_core net/core/dev.c:5636 [inline]
 __netif_receive_skb+0xd7/0x2a0 net/core/dev.c:5750
 netif_receive_skb_internal net/core/dev.c:5836 [inline]
 netif_receive_skb+0x98/0x3e0 net/core/dev.c:5895
 tun_rx_batched+0x1cb/0x7b0 drivers/net/tun.c:1548
 tun_get_user+0x2456/0x32f0 drivers/net/tun.c:1998
 tun_chr_write_iter+0x1f9/0x300 drivers/net/tun.c:2044
 call_write_iter include/linux/fs.h:2282 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ef/0xd00 fs/read_write.c:584
 ksys_write+0x14a/0x260 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:646
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888123972000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 72 bytes inside of
 512-byte region [ffff888123972000, ffff888123972200)

The buggy address belongs to the physical page:
page:ffffea00048e5c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x123970
head:ffffea00048e5c00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 ffff888100042f00
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 306, tgid 306 (syz-executor366), ts 20556203375, free_ts 20556134305
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2680
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3e0 mm/slub.c:2020
 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177
 __slab_alloc+0x5e/0xa0 mm/slub.c:3263
 slab_alloc_node mm/slub.c:3348 [inline]
 __kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423
 __do_kmalloc_node mm/slab_common.c:937 [inline]
 __kmalloc+0xa4/0x1e0 mm/slab_common.c:951
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 new_dir fs/proc/proc_sysctl.c:973 [inline]
 get_subdir fs/proc/proc_sysctl.c:1017 [inline]
 __register_sysctl_table+0x947/0xe50 fs/proc/proc_sysctl.c:1379
 register_net_sysctl+0x23f/0x250 net/sysctl_net.c:169
 neigh_sysctl_register+0x9a0/0xa80 net/core/neighbour.c:3860
 addrconf_sysctl_register+0xb3/0x1a0 net/ipv6/addrconf.c:7235
 ipv6_add_dev+0xbf5/0x1130 net/ipv6/addrconf.c:455
 addrconf_notify+0x6d0/0xe30 net/ipv6/addrconf.c:3621
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1581 [inline]
 free_pcp_prepare mm/page_alloc.c:1655 [inline]
 free_unref_page_prepare+0x81b/0x820 mm/page_alloc.c:3622
 free_unref_page+0x93/0x530 mm/page_alloc.c:3720
 free_the_page mm/page_alloc.c:863 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:6021
 free_pages+0x82/0x90 mm/page_alloc.c:6032
 __stack_depot_save+0x45f/0x490 lib/stackdepot.c:506
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_set_track+0x60/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:380 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 kmalloc_trace+0x40/0xb0 mm/slab_common.c:1033
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 ipv6_add_dev+0xfb/0x1130 net/ipv6/addrconf.c:383
 addrconf_notify+0x6d0/0xe30 net/ipv6/addrconf.c:3621
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
 call_netdevice_notifiers_info net/core/dev.c:2022 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2060 [inline]
 call_netdevice_notifiers+0x119/0x190 net/core/dev.c:2074
 register_netdevice+0x1186/0x1550 net/core/dev.c:10240
 tun_set_iff+0x831/0xee0 drivers/net/tun.c:2854
 __tun_chr_ioctl+0x88c/0x1ef0 drivers/net/tun.c:3117

Memory state around the buggy address:
 ffff888123971f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888123971f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888123972000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888123972080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888123972100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/11/14 22:19 android14-6.1 c1e1dfc6e051 819ebe34 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in __ipv6_addr_type
* Struck through repros no longer work on HEAD.