syzbot

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BUG: KASAN: slab-use-after-free in hlist_add_head_rcu include/linux/rculist.h:642 [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 ffff888027b476a8 by task syz.5.3980/26107

CPU: 1 UID: 0 PID: 26107 Comm: syz.5.3980 Not tainted 6.16.0-rc6-next-20250718-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 hlist_add_head_rcu include/linux/rculist.h:642 [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+0x6ef/0x8c0 net/ipv6/anycast.c:153
 do_ipv6_setsockopt+0x1e90/0x2eb0 net/ipv6/ipv6_sockglue.c:897
 ipv6_setsockopt+0x59/0x170 net/ipv6/ipv6_sockglue.c:969
 do_sock_setsockopt+0x179/0x1b0 net/socket.c:2344
 __sys_setsockopt net/socket.c:2369 [inline]
 __do_sys_setsockopt net/socket.c:2375 [inline]
 __se_sys_setsockopt net/socket.c:2372 [inline]
 __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2372
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f813578e9a9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f813659e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f81359b5fa0 RCX: 00007f813578e9a9
RDX: 000000000000001b RSI: 0000000000000029 RDI: 0000000000000000
RBP: 00007f8135810d69 R08: 0000000000000014 R09: 0000000000000000
R10: 00002000000000c0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f81359b5fa0 R15: 00007ffed6d57798
 </TASK>

Allocated by task 0:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4365 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4377
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 cfg80211_inform_single_bss_data+0x905/0x1ac0 net/wireless/scan.c:2351
 cfg80211_inform_bss_data+0x1fb/0x3b20 net/wireless/scan.c:3234
 cfg80211_inform_bss_frame_data+0x3d7/0x730 net/wireless/scan.c:3325
 ieee80211_bss_info_update+0x746/0x9e0 net/mac80211/scan.c:226
 ieee80211_scan_rx+0x593/0xa20 net/mac80211/scan.c:355
 __ieee80211_rx_handle_packet net/mac80211/rx.c:5170 [inline]
 ieee80211_rx_list+0x2067/0x2d50 net/mac80211/rx.c:5407
 ieee80211_rx_napi+0x1a8/0x3d0 net/mac80211/rx.c:5430
 ieee80211_rx include/net/mac80211.h:5206 [inline]
 ieee80211_handle_queued_frames+0xe8/0x1f0 net/mac80211/main.c:442
 tasklet_action_common+0x369/0x580 kernel/softirq.c:829
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Freed by task 2995:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2417 [inline]
 slab_free_freelist_hook mm/slub.c:2446 [inline]
 slab_free_bulk mm/slub.c:4704 [inline]
 kmem_cache_free_bulk+0x2d1/0x520 mm/slub.c:5283
 kfree_bulk include/linux/slab.h:794 [inline]
 kvfree_rcu_bulk+0xe5/0x1f0 mm/slab_common.c:1516
 kfree_rcu_work+0xed/0x170 mm/slab_common.c:1594
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:548
 kvfree_call_rcu+0xbb/0x410 mm/slab_common.c:1962
 cfg80211_update_known_bss+0x634/0x1330 net/wireless/scan.c:1936
 __cfg80211_bss_update+0x147/0x2120 net/wireless/scan.c:1983
 cfg80211_inform_single_bss_data+0xba9/0x1ac0 net/wireless/scan.c:2375
 cfg80211_inform_bss_data+0x1fb/0x3b20 net/wireless/scan.c:3234
 cfg80211_inform_bss_frame_data+0x3d7/0x730 net/wireless/scan.c:3325
 ieee80211_bss_info_update+0x746/0x9e0 net/mac80211/scan.c:226
 ieee80211_rx_bss_info net/mac80211/ibss.c:1094 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1573 [inline]
 ieee80211_ibss_rx_queued_mgmt+0xa36/0x2ae0 net/mac80211/ibss.c:1600
 ieee80211_iface_process_skb net/mac80211/iface.c:1699 [inline]
 ieee80211_iface_work+0x85f/0x12d0 net/mac80211/iface.c:1753
 cfg80211_wiphy_work+0x2bb/0x470 net/wireless/core.c:435
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888027b47680
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 40 bytes inside of
 freed 96-byte region [ffff888027b47680, ffff888027b476e0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888027b47f80 pfn:0x27b47
ksm flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801a841280 ffffea0000cbfe80 dead000000000003
raw: ffff888027b47f80 000000000020001b 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 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5918, tgid 5918 (kworker/1:4), ts 95566135617, free_ts 95456388776
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2487 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2655
 new_slab mm/slub.c:2709 [inline]
 ___slab_alloc+0xbeb/0x1410 mm/slub.c:3891
 __slab_alloc mm/slub.c:3981 [inline]
 __slab_alloc_node mm/slub.c:4056 [inline]
 slab_alloc_node mm/slub.c:4217 [inline]
 __kmalloc_cache_noprof+0x296/0x3d0 mm/slub.c:4391
 kmalloc_noprof include/linux/slab.h:905 [inline]
 dst_cow_metrics_generic+0x56/0x1c0 net/core/dst.c:193
 dst_metrics_write_ptr include/net/dst.h:133 [inline]
 dst_metric_set include/net/dst.h:194 [inline]
 icmp6_dst_alloc+0x261/0x420 net/ipv6/route.c:3337
 mld_sendpack+0x678/0xd80 net/ipv6/mcast.c:1849
 mld_dad_work+0x46/0x490 net/ipv6/mcast.c:2299
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 5846 tgid 5846 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2895
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0xca5/0x1710 kernel/rcu/tree.c:2861
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

Memory state around the buggy address:
 ffff888027b47580: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
 ffff888027b47600: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff888027b47680: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                  ^
 ffff888027b47700: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
 ffff888027b47780: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
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