[syzbot] [kernel?] KASAN: slab-use-after-free Read in irq_migrate_all_off_this_cpu

[syzbot <syzbot+e293654450a72d8e7875@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    2709dd5ae32f Merge tag 'sched-urgent-2026-08-22' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=141d2415580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=549777c32aabcf9c
dashboard link: https://syzkaller.appspot.com/bug?extid=e293654450a72d8e7875
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-2709dd5a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d2178ccb53ea/vmlinux-2709dd5a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/84740cfe4163/bzImage-2709dd5a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e293654450a72d8e7875@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in irq_can_move_pcntxt kernel/irq/internals.h:328 [inline]
BUG: KASAN: slab-use-after-free in migrate_one_irq kernel/irq/cpuhotplug.c:57 [inline]
BUG: KASAN: slab-use-after-free in irq_migrate_all_off_this_cpu+0xaaf/0xc30 kernel/irq/cpuhotplug.c:181
Read of size 8 at addr ffff88806e9f29a8 by task migration/1/27

CPU: 1 UID: 0 PID: 27 Comm: migration/1 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Stopper: multi_cpu_stop+0x0/0x4b0 kernel/stop_machine.c:199 <- __stop_cpus.constprop.0+0xb1/0x140
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+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 irq_can_move_pcntxt kernel/irq/internals.h:328 [inline]
 migrate_one_irq kernel/irq/cpuhotplug.c:57 [inline]
 irq_migrate_all_off_this_cpu+0xaaf/0xc30 kernel/irq/cpuhotplug.c:181
 fixup_irqs+0x2b/0x280 arch/x86/kernel/irq.c:474
 cpu_disable_common arch/x86/kernel/smpboot.c:1371 [inline]
 native_cpu_disable+0x59/0x80 arch/x86/kernel/smpboot.c:1383
 __cpu_disable arch/x86/include/asm/smp.h:73 [inline]
 take_cpu_down+0xb6/0x190 kernel/cpu.c:1282
 multi_cpu_stop+0x16a/0x4b0 kernel/stop_machine.c:239
 cpu_stopper_thread+0x21e/0x450 kernel/stop_machine.c:510
 smpboot_thread_fn+0x3d3/0xab0 kernel/smpboot.c:160
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 8406:
 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:5337 [inline]
 __kmalloc_noprof+0x324/0x820 mm/slub.c:5362
 _kmalloc_noprof include/linux/slab.h:992 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 neigh_alloc net/core/neighbour.c:518 [inline]
 ___neigh_create+0x1532/0x2940 net/core/neighbour.c:652
 ip6_finish_output2+0x1052/0x1d50 net/ipv6/ip6_output.c:130
 __ip6_finish_output+0x357/0xdf0 net/ipv6/ip6_output.c:210
 ip6_finish_output net/ipv6/ip6_output.c:221 [inline]
 NF_HOOK_COND include/linux/netfilter.h:314 [inline]
 ip6_output+0x2aa/0xa60 net/ipv6/ip6_output.c:248
 dst_output include/net/dst.h:470 [inline]
 NF_HOOK include/linux/netfilter.h:325 [inline]
 ndisc_send_skb+0xa85/0x1bf0 net/ipv6/ndisc.c:513
 ndisc_send_rs+0x129/0x680 net/ipv6/ndisc.c:724
 addrconf_dad_completed+0x47f/0xff0 net/ipv6/addrconf.c:4396
 addrconf_dad_work+0x83c/0x1360 net/ipv6/addrconf.c:4304
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3387
 process_scheduled_works kernel/workqueue.c:3470 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3551
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 55:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2678 [inline]
 slab_free_freelist_hook mm/slub.c:2707 [inline]
 slab_free_bulk mm/slub.c:6406 [inline]
 kmem_cache_free_bulk mm/slub.c:7143 [inline]
 kmem_cache_free_bulk+0x258/0x730 mm/slub.c:7122
 kfree_bulk include/linux/slab.h:910 [inline]
 kvfree_rcu_bulk+0x176/0x190 mm/slab_common.c:1519
 kfree_rcu_work+0x122/0x1a0 mm/slab_common.c:1597
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3387
 process_scheduled_works kernel/workqueue.c:3470 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3551
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 kvfree_call_rcu+0x6a/0x4f0 mm/slab_common.c:1987
 neigh_destroy+0x436/0x620 net/core/neighbour.c:943
 neigh_release include/net/neighbour.h:459 [inline]
 neigh_cleanup_and_release+0xfa/0x2d0 net/core/neighbour.c:121
 neigh_periodic_work+0x6b6/0xc10 net/core/neighbour.c:1026
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3387
 process_scheduled_works kernel/workqueue.c:3470 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3551
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff88806e9f2800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 424 bytes inside of
 freed 1024-byte region [ffff88806e9f2800, ffff88806e9f2c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88806e9f0000 pfn:0x6e9f0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4fff00000000240(workingset|head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000240 ffff88801c042dc0 ffffea0001433410 ffffea0001aba210
raw: ffff88806e9f0000 0000000800100008 00000000f5000000 0000000000000000
head: 04fff00000000240 ffff88801c042dc0 ffffea0001433410 ffffea0001aba210
head: ffff88806e9f0000 0000000800100008 00000000f5000000 0000000000000000
head: 04fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 61, tgid 61 (kworker/3:1), ts 50400280827
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35b0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3267 [inline]
 allocate_slab mm/slub.c:3382 [inline]
 new_slab+0xa5/0x640 mm/slub.c:3428
 refill_objects+0xe3/0x410 mm/slub.c:7305
 refill_sheaf mm/slub.c:2805 [inline]
 __pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
 alloc_from_pcs mm/slub.c:4775 [inline]
 slab_alloc_node mm/slub.c:4907 [inline]
 __do_kmalloc_node mm/slub.c:5336 [inline]
 __kmalloc_noprof+0x66b/0x820 mm/slub.c:5362
 _kmalloc_noprof include/linux/slab.h:992 [inline]
 _kzalloc_noprof include/linux/slab.h:1309 [inline]
 ieee802_11_parse_elems_full+0x17c/0x3c90 net/mac80211/parse.c:1071
 ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2548 [inline]
 ieee80211_inform_bss+0x159/0x1170 net/mac80211/scan.c:79
 rdev_inform_bss net/wireless/rdev-ops.h:418 [inline]
 cfg80211_inform_single_bss_data+0x898/0x1dc0 net/wireless/scan.c:2410
 cfg80211_inform_bss_data+0x230/0x3c20 net/wireless/scan.c:3266
 cfg80211_inform_bss_frame_data+0x245/0x7c0 net/wireless/scan.c:3358
 ieee80211_bss_info_update+0x310/0xab0 net/mac80211/scan.c:230
 ieee80211_scan_rx+0x4e6/0xb60 net/mac80211/scan.c:364
 __ieee80211_rx_handle_packet+0xbab/0xfc0 net/mac80211/rx.c:5427
 ieee80211_rx_list+0xf19/0x2160 net/mac80211/rx.c:5720
page last free pid 5140 tgid 5140 ts 50393821474 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x79f/0x10f0 mm/page_alloc.c:2962
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 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:4586 [inline]
 slab_alloc_node mm/slub.c:4919 [inline]
 kmem_cache_alloc_noprof+0x26b/0x6a0 mm/slub.c:4933
 alloc_filename fs/namei.c:147 [inline]
 do_getname+0x35/0x390 fs/namei.c:187
 class_filename_flags_constructor include/linux/fs.h:2587 [inline]
 do_sys_openat2+0xc7/0x1e0 fs/open.c:1416
 do_sys_open fs/open.c:1423 [inline]
 __do_sys_openat fs/open.c:1439 [inline]
 __se_sys_openat fs/open.c:1434 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1434
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88806e9f2880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806e9f2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806e9f2980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88806e9f2a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806e9f2a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup