From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f80.google.com (mail-oa1-f80.google.com [209.85.160.80]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B72D92C21FE for ; Sat, 31 Jan 2026 09:49:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769852970; cv=none; b=Ts1WTFcCVLx8BPIS/b2Iynrbq3bLiOqB11foneDUEGQ8Km2WsoGXcnSdLrPXdvwQcNjyYqNsiuh8gRMJOmZF96ruxjSaaMlCU+tpziVH8TvcmNKho4yr2+E4SOTaLxqKecEzZUCs6zkPO32DkUWkfBKSZBKG57sYiEa1VaMAOqk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769852970; c=relaxed/simple; bh=/ks4b6pp0susYSFfnNG3DLwHfn9h11l6YCNj0wrWAmY=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=fxUUyfc4CHMBGzTNyhrNUP0FM0MK92ZOwrecAyXSIIrYzqWIbZeL7T4hFUcXAZdGkYiHK0bLX0HNaEUt3CeU1aizHeMTWziPNlyiJaT7ZQKdp1PgzytrpXf8lQEnd7J1RRk9Tji8qd6WbxqI197VVETZzKcfUlaKlUF+zuflLWA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.160.80 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oa1-f80.google.com with SMTP id 586e51a60fabf-4096f92cf50so6554750fac.3 for ; Sat, 31 Jan 2026 01:49:28 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769852967; x=1770457767; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=sk0dwA9mXpxiPETTlMSUdfR5P+at6XuhGJ8JtKY8jYA=; b=E5B8xom2oqmA655K6+6lekZM9S+tIEPaWTTq1CocSxqJJJUMy6bkve/mOb2obCMY1D 4u7FDkKgJa05zE1YHg8YQeDjrYUsb0s7c4okEaLmIXiGZb4O+N0HWocaDxQggW20f5Yg 9nbth8J0EVuqbU0A8WQT5qQP0qUaflw377OWQwOoAG5OsAW0WOffF5NRsGNCl4inJE1d lv/Za7nfIjRa1f5S8ES3HVnwNx8e35H3a5N8Lme7TBmGYe6WUt/QKfKZ9RqoYRRqlYAh laiqWz/vmueg13dMXlrZ7cLVfq/YQhN4RhLq1POPxDwLYl9g/I8xGIjws+2xtdDtg92r DAZg== X-Forwarded-Encrypted: i=1; AJvYcCWxkjzkyPDKuUgkI09L2Y433jKZMf+YcOcRN+rkbT1sRTsGcy3GgKIuJkpB6wobrVllzxvhP8I=@vger.kernel.org X-Gm-Message-State: AOJu0YyZwH/Hw+J50Z5leK6zyFJbjwnd+CFVB9Je/oU/GhyisMBvI/ff tqRADFL5cmNHmdr8NRH5OiCXOZz6+/blyd6jGtpamDyee+HwaCAic7ldeUGG/lkLpThVP1fKnbD rYBnd6dhzIvn97g716J8340f8/M+nJ62HHzEZdugyXdBb/2KlYHA2ZD04TBI= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:60f:b0:662:fe6d:619f with SMTP id 006d021491bc7-6630ef5f752mr2430640eaf.0.1769852967511; Sat, 31 Jan 2026 01:49:27 -0800 (PST) Date: Sat, 31 Jan 2026 01:49:27 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <697dd027.050a0220.1d0a41.0005.GAE@google.com> Subject: [syzbot] [hams?] KASAN: slab-use-after-free Write in nr_neigh_put From: syzbot To: davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, linux-hams@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 6ad42b244136 Merge branch 'bng_en-enhancements-for-rx-and-.. git tree: net-next console output: https://syzkaller.appspot.com/x/log.txt?x=1421a72a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=2c36acc86fd56a9d dashboard link: https://syzkaller.appspot.com/bug?extid=08ca620c862d89afe6d6 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/2b03def814aa/disk-6ad42b24.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/e677d64cb110/vmlinux-6ad42b24.xz kernel image: https://storage.googleapis.com/syzbot-assets/e89660ed5369/bzImage-6ad42b24.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+08ca620c862d89afe6d6@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline] BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline] BUG: KASAN: slab-use-after-free in __refcount_sub_and_test include/linux/refcount.h:389 [inline] BUG: KASAN: slab-use-after-free in __refcount_dec_and_test include/linux/refcount.h:432 [inline] BUG: KASAN: slab-use-after-free in refcount_dec_and_test include/linux/refcount.h:450 [inline] BUG: KASAN: slab-use-after-free in nr_neigh_put+0x21/0x170 include/net/netrom.h:139 Write of size 4 at addr ffff888026ddaf3c by task syz.1.8003/5600 CPU: 0 UID: 0 PID: 5600 Comm: syz.1.8003 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200 instrument_atomic_read_write include/linux/instrumented.h:96 [inline] atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline] __refcount_sub_and_test include/linux/refcount.h:389 [inline] __refcount_dec_and_test include/linux/refcount.h:432 [inline] refcount_dec_and_test include/linux/refcount.h:450 [inline] nr_neigh_put+0x21/0x170 include/net/netrom.h:139 nr_del_neigh+0x25a/0x2d0 net/netrom/nr_route.c:440 nr_rt_ioctl+0xd62/0xf90 net/netrom/nr_route.c:682 sock_do_ioctl+0x101/0x320 net/socket.c:1254 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3bd0f9aeb9 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:00007f3bd1d7a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f3bd1216090 RCX: 00007f3bd0f9aeb9 RDX: 0000200000000680 RSI: 000000000000890c RDI: 0000000000000006 RBP: 00007f3bd1008c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3bd1216128 R14: 00007f3bd1216090 R15: 00007fffa738a9e8 Allocated by task 5599: 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_noprof+0x3d1/0x6e0 mm/slub.c:5780 kmalloc_noprof include/linux/slab.h:957 [inline] nr_add_neigh+0x104/0x520 net/netrom/nr_route.c:392 nr_rt_ioctl+0xdf9/0xf90 net/netrom/nr_route.c:660 sock_do_ioctl+0x101/0x320 net/socket.c:1254 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5600: 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:2540 [inline] slab_free mm/slub.c:6674 [inline] kfree+0x1be/0x650 mm/slub.c:6882 __nr_remove_neigh net/netrom/nr_route.c:299 [inline] nr_remove_neigh net/netrom/nr_route.c:308 [inline] nr_del_neigh+0x246/0x2d0 net/netrom/nr_route.c:439 nr_rt_ioctl+0xd62/0xf90 net/netrom/nr_route.c:682 sock_do_ioctl+0x101/0x320 net/socket.c:1254 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff888026ddaf00 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 60 bytes inside of freed 64-byte region [ffff888026ddaf00, ffff888026ddaf40) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26dda ksm flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000000 ffff88813fe268c0 ffffea0000a56ec0 dead000000000003 raw: 0000000000000000 0000000080200020 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5835, tgid 5835 (syz-executor), ts 88717173954, free_ts 88621883212 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884 prep_new_page mm/page_alloc.c:1892 [inline] get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486 alloc_slab_page mm/slub.c:3075 [inline] allocate_slab+0x86/0x3a0 mm/slub.c:3248 new_slab mm/slub.c:3302 [inline] ___slab_alloc+0xd82/0x1760 mm/slub.c:4656 __slab_alloc+0x65/0x100 mm/slub.c:4779 __slab_alloc_node mm/slub.c:4855 [inline] slab_alloc_node mm/slub.c:5251 [inline] __do_kmalloc_node mm/slub.c:5656 [inline] __kmalloc_noprof+0x46c/0x7e0 mm/slub.c:5669 kmalloc_noprof include/linux/slab.h:961 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] tnode_alloc net/ipv4/fib_trie.c:327 [inline] tnode_new+0xc3/0x3b0 net/ipv4/fib_trie.c:380 fib_insert_node net/ipv4/fib_trie.c:1125 [inline] fib_insert_alias+0x9f7/0x1100 net/ipv4/fib_trie.c:1159 fib_table_insert+0x695/0x1b50 net/ipv4/fib_trie.c:1354 fib_magic+0x434/0x510 net/ipv4/fib_frontend.c:1134 fib_add_ifaddr+0x144/0x5f0 net/ipv4/fib_frontend.c:1156 fib_inetaddr_event+0x12e/0x190 net/ipv4/fib_frontend.c:1470 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 blocking_notifier_call_chain+0x6a/0x90 kernel/notifier.c:380 page last free pid 5832 tgid 5832 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1433 [inline] __free_frozen_pages+0xbf8/0xd70 mm/page_alloc.c:2973 rcu_do_batch kernel/rcu/tree.c:2605 [inline] rcu_core+0xc9e/0x1750 kernel/rcu/tree.c:2857 handle_softirqs+0x22a/0x7c0 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 Memory state around the buggy address: ffff888026ddae00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff888026ddae80: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc >ffff888026ddaf00: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ffff888026ddaf80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff888026ddb000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== --- 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