KASAN: slab-use-after-free Write in __ipv6_dev_ac_inc (2)

Status: auto-obsoleted due to no activity on 2026/07/30 16:26
Subsystems: net
Labels: prio:high
[Documentation on labels]
First crash: 110d, last: 106d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
b0ad171c assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Write in __ipv6_dev_ac_inc (2) 2026/05/30 08:47 2026/05/30 08:47 2026/05/30 10:01 6b4a8443
7dc9eaa1 assessment-security 💥 KASAN: slab-use-after-free Write in __ipv6_dev_ac_inc (2) 2026/05/14 09:19 2026/05/14 09:19 2026/05/14 09:20 6ccb967e
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Write in __ipv6_dev_ac_inc net 22 1 380d 380d 0/29 closed as invalid on 2025/09/01 08:24

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in hlist_add_head_rcu include/linux/rculist.h:652 [inline]
BUG: KASAN: slab-use-after-free in ipv6_add_acaddr_hash net/ipv6/anycast.c:247 [inline]
BUG: KASAN: slab-use-after-free in __ipv6_dev_ac_inc+0x774/0xaf0 net/ipv6/anycast.c:376
Write of size 8 at addr ffff88802129eea8 by task syz.1.2697/19657

CPU: 0 UID: 0 PID: 19657 Comm: syz.1.2697 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 hlist_add_head_rcu include/linux/rculist.h:652 [inline]
 ipv6_add_acaddr_hash net/ipv6/anycast.c:247 [inline]
 __ipv6_dev_ac_inc+0x774/0xaf0 net/ipv6/anycast.c:376
 ipv6_sock_ac_join+0x6a8/0x880 net/ipv6/anycast.c:153
 do_ipv6_setsockopt+0x203a/0x3150 net/ipv6/ipv6_sockglue.c:893
 ipv6_setsockopt+0x59/0x170 net/ipv6/ipv6_sockglue.c:965
 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2381
 __sys_setsockopt net/socket.c:2406 [inline]
 __do_sys_setsockopt net/socket.c:2412 [inline]
 __se_sys_setsockopt net/socket.c:2409 [inline]
 __x64_sys_setsockopt+0x13d/0x1b0 net/socket.c:2409
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fea8af9c819
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:00007fea88db2028 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007fea8b216270 RCX: 00007fea8af9c819
RDX: 000000000000001b RSI: 0000000000000029 RDI: 000000000000000a
RBP: 00007fea8b032c91 R08: 0000000000000014 R09: 0000000000000000
R10: 0000200000000140 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fea8b216308 R14: 00007fea8b216270 R15: 00007fea8b33fa48
 </TASK>

Allocated by task 5857:
 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]
 __kmalloc_cache_node_noprof+0x3ef/0x6b0 mm/slub.c:5427
 kmalloc_node_noprof include/linux/slab.h:1077 [inline]
 __get_vm_area_node+0x13f/0x300 mm/vmalloc.c:3215
 __vmalloc_node_range_noprof+0x36a/0x1750 mm/vmalloc.c:4024
 __vmalloc_node_noprof mm/vmalloc.c:4124 [inline]
 vzalloc_noprof+0xb2/0xe0 mm/vmalloc.c:4202
 alloc_counters+0x64/0x5d0 net/ipv4/netfilter/ip_tables.c:799
 copy_entries_to_user net/ipv4/netfilter/ip_tables.c:821 [inline]
 get_entries net/ipv4/netfilter/ip_tables.c:1022 [inline]
 do_ipt_get_ctl+0xada/0x1240 net/ipv4/netfilter/ip_tables.c:1668
 nf_getsockopt+0x26e/0x290 net/netfilter/nf_sockopt.c:116
 ip_getsockopt+0x19e/0x230 net/ipv4/ip_sockglue.c:1777
 do_sock_getsockopt+0x51d/0x7e0 net/socket.c:2487
 __sys_getsockopt net/socket.c:2518 [inline]
 __do_sys_getsockopt net/socket.c:2525 [inline]
 __se_sys_getsockopt net/socket.c:2522 [inline]
 __x64_sys_getsockopt+0x1a4/0x240 net/socket.c:2522
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5857:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6246 [inline]
 kfree+0x1c5/0x640 mm/slub.c:6561
 copy_entries_to_user net/ipv4/netfilter/ip_tables.c:866 [inline]
 get_entries net/ipv4/netfilter/ip_tables.c:1022 [inline]
 do_ipt_get_ctl+0xf25/0x1240 net/ipv4/netfilter/ip_tables.c:1668
 nf_getsockopt+0x26e/0x290 net/netfilter/nf_sockopt.c:116
 ip_getsockopt+0x19e/0x230 net/ipv4/ip_sockglue.c:1777
 do_sock_getsockopt+0x51d/0x7e0 net/socket.c:2487
 __sys_getsockopt net/socket.c:2518 [inline]
 __do_sys_getsockopt net/socket.c:2525 [inline]
 __se_sys_getsockopt net/socket.c:2522 [inline]
 __x64_sys_getsockopt+0x1a4/0x240 net/socket.c:2522
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802129ee80
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 40 bytes inside of
 freed 96-byte region [ffff88802129ee80, ffff88802129eee0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88802129e000 pfn:0x2129e
flags: 0xfff00000000200(workingset|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000200 ffff88813fe2e280 ffffea00007fc7d0 ffffea0001f9ded0
raw: ffff88802129e000 000000080020000b 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5932, tgid 5932 (kworker/1:5), ts 88505902237, free_ts 88505719345
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x24ba/0x2540 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3467
 new_slab mm/slub.c:3525 [inline]
 refill_objects+0x339/0x3d0 mm/slub.c:7251
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __kmalloc_cache_noprof+0x392/0x660 mm/slub.c:5410
 kmalloc_noprof include/linux/slab.h:950 [inline]
 dst_cow_metrics_generic+0x56/0x1c0 net/core/dst.c:194
 dst_metrics_write_ptr include/net/dst.h:136 [inline]
 dst_metric_set include/net/dst.h:197 [inline]
 icmp6_dst_alloc+0x265/0x440 net/ipv6/route.c:3350
 mld_sendpack+0x6ba/0xe40 net/ipv6/mcast.c:1844
 mld_dad_work+0x45/0x5b0 net/ipv6/mcast.c:2294
 process_one_work kernel/workqueue.c:3302 [inline]
 process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 5932 tgid 5932 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0xbc7/0xd30 mm/page_alloc.c:2943
 __slab_free+0x274/0x2c0 mm/slub.c:5608
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 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:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 kmem_cache_alloc_node_noprof+0x384/0x690 mm/slub.c:4950
 __alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
 alloc_skb include/linux/skbuff.h:1383 [inline]
 mld_newpack+0x14c/0xc90 net/ipv6/mcast.c:1775
 add_grhead+0x5a/0x2a0 net/ipv6/mcast.c:1886
 add_grec+0x1452/0x1740 net/ipv6/mcast.c:2025
 mld_send_initial_cr+0x288/0x550 net/ipv6/mcast.c:2268
 mld_dad_work+0x45/0x5b0 net/ipv6/mcast.c:2294
 process_one_work kernel/workqueue.c:3302 [inline]
 process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158

Memory state around the buggy address:
 ffff88802129ed80: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff88802129ee00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88802129ee80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                  ^
 ffff88802129ef00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88802129ef80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/23 15:13 upstream 2e6803928193 4c3406dc .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Write in __ipv6_dev_ac_inc
2026/04/27 14:31 upstream 254f49634ee1 0f700595 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Write in __ipv6_dev_ac_inc
* Struck through repros no longer work on HEAD.