On 11/3/25 13:20, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: fd57572253bc Merge tag 'sched_ext-for-6.18-rc3-fixes' of g.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13f957e2580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=609c87dcb0628493 > dashboard link: https://syzkaller.appspot.com/bug?extid=dd280197f0f7ab3917be > compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils > for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: > https://storage.googleapis.com/syzbot-assets/a4541b741dd8/disk-fd575722.raw.xz > vmlinux: > https://storage.googleapis.com/syzbot-assets/eae4ddf523dd/vmlinux-fd575722.xz > kernel image: > https://storage.googleapis.com/syzbot-assets/28e03b35c3fc/bzImage-fd575722.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: [email protected] > > ================================================================== > BUG: KASAN: slab-use-after-free in br_switchdev_fdb_populate+0x390/0x3a0 > net/bridge/br_switchdev.c:141 > Read of size 8 at addr ffff888025122808 by task kworker/0:2/977 >
hmm I have an idea about this one, it's possibly related to MST enabled && vlan filtering disabled. I'll try to repro and post a fix if I'm correct. Cheers, Nik > CPU: 0 UID: 0 PID: 977 Comm: kworker/0:2 Not tainted syzkaller #0 > PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 10/02/2025 > Workqueue: events_long br_fdb_cleanup > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:94 [inline] > dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 > print_address_description mm/kasan/report.c:378 [inline] > print_report+0xcd/0x630 mm/kasan/report.c:482 > kasan_report+0xe0/0x110 mm/kasan/report.c:595 > br_switchdev_fdb_populate+0x390/0x3a0 net/bridge/br_switchdev.c:141 > br_switchdev_fdb_notify+0x1df/0x2c0 net/bridge/br_switchdev.c:165 > fdb_notify+0x16c/0x1a0 net/bridge/br_fdb.c:186 > fdb_delete+0x76e/0x12a0 net/bridge/br_fdb.c:324 > br_fdb_cleanup+0x43e/0x600 net/bridge/br_fdb.c:574 > process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263 > process_scheduled_works kernel/workqueue.c:3346 [inline] > worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427 > kthread+0x3c5/0x780 kernel/kthread.c:463 > ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > </TASK> > > Allocated by task 5810: > kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 > kasan_save_track+0x14/0x30 mm/kasan/common.c:77 > poison_kmalloc_redzone mm/kasan/common.c:400 [inline] > __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417 > kmalloc_noprof include/linux/slab.h:957 [inline] > kzalloc_noprof include/linux/slab.h:1094 [inline] > new_nbp net/bridge/br_if.c:431 [inline] > br_add_if+0x41d/0x1b70 net/bridge/br_if.c:599 > do_set_master+0x40f/0x730 net/core/rtnetlink.c:2956 > do_setlink.constprop.0+0xbd8/0x4380 net/core/rtnetlink.c:3158 > rtnl_changelink net/core/rtnetlink.c:3769 [inline] > __rtnl_newlink net/core/rtnetlink.c:3928 [inline] > rtnl_newlink+0x1446/0x2000 net/core/rtnetlink.c:4065 > rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6951 > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552 > netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 > netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 > sock_sendmsg_nosec net/socket.c:727 [inline] > __sock_sendmsg net/socket.c:742 [inline] > __sys_sendto+0x4a3/0x520 net/socket.c:2244 > __do_sys_sendto net/socket.c:2251 [inline] > __se_sys_sendto net/socket.c:2247 [inline] > __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2247 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > Freed by task 15061: > kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 > kasan_save_track+0x14/0x30 mm/kasan/common.c:77 > __kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:587 > kasan_save_free_info mm/kasan/kasan.h:406 [inline] > poison_slab_object mm/kasan/common.c:252 [inline] > __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:284 > kasan_slab_free include/linux/kasan.h:234 [inline] > slab_free_hook mm/slub.c:2539 [inline] > slab_free mm/slub.c:6630 [inline] > kfree+0x2b8/0x6d0 mm/slub.c:6837 > kobject_cleanup lib/kobject.c:689 [inline] > kobject_release lib/kobject.c:720 [inline] > kref_put include/linux/kref.h:65 [inline] > kobject_put+0x1e7/0x5a0 lib/kobject.c:737 > rcu_do_batch kernel/rcu/tree.c:2605 [inline] > rcu_core+0x79c/0x1530 kernel/rcu/tree.c:2861 > handle_softirqs+0x219/0x8e0 kernel/softirq.c:622 > __do_softirq kernel/softirq.c:656 [inline] > invoke_softirq kernel/softirq.c:496 [inline] > __irq_exit_rcu+0x109/0x170 kernel/softirq.c:723 > irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 > instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] > sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1052 > asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 > > Last potentially related work creation: > kasan_save_stack+0x33/0x60 mm/kasan/common.c:56 > kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:559 > __call_rcu_common.constprop.0+0xa5/0xa10 kernel/rcu/tree.c:3123 > br_del_if+0xe0/0x270 net/bridge/br_if.c:740 > do_set_master+0x172/0x730 net/core/rtnetlink.c:2940 > do_setlink.constprop.0+0xbd8/0x4380 net/core/rtnetlink.c:3158 > rtnl_group_changelink net/core/rtnetlink.c:3783 [inline] > __rtnl_newlink net/core/rtnetlink.c:3937 [inline] > rtnl_newlink+0x18e0/0x2000 net/core/rtnetlink.c:4065 > rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6951 > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552 > netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 > netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 > sock_sendmsg_nosec net/socket.c:727 [inline] > __sock_sendmsg net/socket.c:742 [inline] > ____sys_sendmsg+0xa98/0xc70 net/socket.c:2630 > ___sys_sendmsg+0x134/0x1d0 net/socket.c:2684 > __sys_sendmsg+0x16d/0x220 net/socket.c:2716 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > The buggy address belongs to the object at ffff888025122800 > which belongs to the cache kmalloc-1k of size 1024 > The buggy address is located 8 bytes inside of > freed 1024-byte region [ffff888025122800, ffff888025122c00) > > The buggy address belongs to the physical page: > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888025125800 > pfn:0x25120 > head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 > flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff) > page_type: f5(slab) > raw: 00fff00000000240 ffff88813ffa6dc0 ffffea0001ee1810 ffffea0000c8c210 > raw: ffff888025125800 000000000010000e 00000000f5000000 0000000000000000 > head: 00fff00000000240 ffff88813ffa6dc0 ffffea0001ee1810 ffffea0000c8c210 > head: ffff888025125800 000000000010000e 00000000f5000000 0000000000000000 > head: 00fff00000000003 ffffea0000944801 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 > 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), > pid 5807, tgid 5807 (syz-executor), ts 72613372336, free_ts 72596370994 > set_page_owner include/linux/page_owner.h:32 [inline] > post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1850 > prep_new_page mm/page_alloc.c:1858 [inline] > get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3884 > __alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5183 > alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416 > alloc_slab_page mm/slub.c:3055 [inline] > allocate_slab mm/slub.c:3228 [inline] > new_slab+0x24a/0x360 mm/slub.c:3282 > ___slab_alloc+0xdae/0x1a60 mm/slub.c:4651 > __slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4770 > __slab_alloc_node mm/slub.c:4846 [inline] > slab_alloc_node mm/slub.c:5268 [inline] > __do_kmalloc_node mm/slub.c:5641 [inline] > __kmalloc_noprof+0x501/0x880 mm/slub.c:5654 > kmalloc_noprof include/linux/slab.h:961 [inline] > kzalloc_noprof include/linux/slab.h:1094 [inline] > __alloc_workqueue+0x112/0x1810 kernel/workqueue.c:5715 > alloc_workqueue_noprof+0xd2/0x200 kernel/workqueue.c:5818 > wg_newlink+0x24d/0x780 drivers/net/wireguard/device.c:341 > rtnl_newlink_create net/core/rtnetlink.c:3833 [inline] > __rtnl_newlink net/core/rtnetlink.c:3950 [inline] > rtnl_newlink+0xc45/0x2000 net/core/rtnetlink.c:4065 > rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6951 > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552 > netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 > netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 > page last free pid 5809 tgid 5809 stack trace: > reset_page_owner include/linux/page_owner.h:25 [inline] > free_pages_prepare mm/page_alloc.c:1394 [inline] > __free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906 > qlink_free mm/kasan/quarantine.c:163 [inline] > qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179 > kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286 > __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:352 > kasan_slab_alloc include/linux/kasan.h:252 [inline] > slab_post_alloc_hook mm/slub.c:4970 [inline] > slab_alloc_node mm/slub.c:5280 [inline] > __kmalloc_cache_noprof+0x274/0x780 mm/slub.c:5758 > kmalloc_noprof include/linux/slab.h:957 [inline] > kzalloc_noprof include/linux/slab.h:1094 [inline] > kset_create lib/kobject.c:965 [inline] > kset_create_and_add+0x4d/0x190 lib/kobject.c:1008 > register_queue_kobjects net/core/net-sysfs.c:2106 [inline] > netdev_register_kobject+0x1ef/0x3d0 net/core/net-sysfs.c:2362 > register_netdevice+0x13dc/0x2270 net/core/dev.c:11294 > ipcaif_newlink+0x73/0x2c0 net/caif/chnl_net.c:452 > rtnl_newlink_create net/core/rtnetlink.c:3833 [inline] > __rtnl_newlink net/core/rtnetlink.c:3950 [inline] > rtnl_newlink+0xc45/0x2000 net/core/rtnetlink.c:4065 > rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6951 > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552 > netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346 > netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1896 > sock_sendmsg_nosec net/socket.c:727 [inline] > __sock_sendmsg net/socket.c:742 [inline] > __sys_sendto+0x4a3/0x520 net/socket.c:2244 > __do_sys_sendto net/socket.c:2251 [inline] > __se_sys_sendto net/socket.c:2247 [inline] > __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2247 > > Memory state around the buggy address: > ffff888025122700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff888025122780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ffff888025122800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff888025122880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff888025122900: 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 [email protected]. > > 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
