From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f77.google.com (mail-oo1-f77.google.com [209.85.161.77]) (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 86E7439F160 for ; Fri, 29 May 2026 05:09:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.77 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780031372; cv=none; b=X/TWI2cc8HZI2iMIOPSEnv30AI4VA2Ymv+j/rJ0J9GmZlBuT5rigSaBX/7/cDMW4nNRMRT9SRbiQ+cM2EH1B1Rz9SL0B1UjKgX5sfTL5oFZjLBiycWG0NWSEjAHTaabmOneiLrVGN0tgLNPnh0lptlKvXpueFEGv87xmvj9VAl8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780031372; c=relaxed/simple; bh=NKcYTPIYqr9Ob6XL6Udn/Il6DnixJy3CvjNRe2/6RC4=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=m3DVNQ/li3a/ZzAqeUPRIXtNUmHF6usDtAIWPr+43lL0hT3MUEURIUhV5nQ9vtmLW0ZV7huOBEVHqAOk7JkaZtk/ezgu1cDSVRDYKpDHbca8gG+iWRn7QKSV0s84iHn6a3zkWXB073Ugyny6pwMI+vFSYdClH4latJAU0H8Xuy4= 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=209.85.161.77 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-oo1-f77.google.com with SMTP id 006d021491bc7-69d874805ebso8652544eaf.3 for ; Thu, 28 May 2026 22:09:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780031367; x=1780636167; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=v1eTMW0iN770HO3o9T8tICVeXH1P+QKE795ALLtpRqo=; b=SNVMDmGDJ6dZQarOCYNUeh7ADI9c+dD2gXIuOamHUgwmv3e5bDyhWiejBSdjPo2Y4Q nq1FOf6X23zz/aL+ye8ZQMi2HxS4pip6yprdKaCXtJk6GnV8Mu0tjJebv8WzDbluq2d+ 3mu5wU2qYGLOW+2eUo++Ryem/8zP8wOCA7EniMeUxHAMkt4UtMU6Fs6sk5jr6ZmOHYUf NnQq24nIU2+Vtwz8twg3NN/fxybaNeStySYvFuFGqIw8uWIdlqo3bGIneCY+mqsMSfDV tzDKKpe4ei9TfV9gkrAJ9yFsO5sG6EG6iiezqAwKsZOSpjBYyiw37C0kvFD64e+KbL/9 WOKA== X-Forwarded-Encrypted: i=1; AFNElJ/gIvM5ogkvRMkcis2/uTIROXmjBU0rCiYGuOiEn83rg8cyHeKhlu1ponZ1eKrBT7JDE6Hv7cA=@vger.kernel.org X-Gm-Message-State: AOJu0Yw65uZZ9HFTMcWsqnAX315NoCrCm4CkUdtovyiKGwXQ81vIiRhm YXkR9c9foIPJng50+1A+UJB0PLBUo/2Y0HiXGMNZMTHZhkEqtP0j5Vli+bH54oaYSF+4or3bafn vIWGhnQAVu6qstsXzaOKI7hyM+5KeCYltnkEAXZIZ7c5rEX9esOipNAWRohU= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1f02:b0:69d:d439:b222 with SMTP id 006d021491bc7-69e03f01429mr773234eaf.14.1780031367463; Thu, 28 May 2026 22:09:27 -0700 (PDT) Date: Thu, 28 May 2026 22:09:27 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a191f87.ce022c6e.138e56.0003.GAE@google.com> Subject: [syzbot] [net?] KASAN: slab-use-after-free Read in ipv6_chk_acast_addr From: syzbot To: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, horms@kernel.org, idosch@nvidia.com, kuba@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: 550604d6c9b9 Add linux-next specific files for 20260521 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1726e47e580000 kernel config: https://syzkaller.appspot.com/x/.config?x=17ab782ed835fc0e dashboard link: https://syzkaller.appspot.com/bug?extid=819eb928d120d2bdad0e 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/ea4e4e647faa/disk-550604d6.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/5ea9373b711c/vmlinux-550604d6.xz kernel image: https://storage.googleapis.com/syzbot-assets/a2f381baa460/bzImage-550604d6.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+819eb928d120d2bdad0e@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in ipv6_chk_acast_addr+0x2c9/0xb20 net/ipv6/anycast.c:504 Read of size 8 at addr ffff88805f5cd510 by task ktimers/0/16 CPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Call Trace: 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 ipv6_chk_acast_addr+0x2c9/0xb20 net/ipv6/anycast.c:504 icmp6_send+0x4c3/0x1b50 net/ipv6/icmp.c:679 icmpv6_send include/linux/icmpv6.h:24 [inline] ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2862 dst_link_failure include/net/dst.h:456 [inline] ipip6_tunnel_xmit net/ipv6/sit.c:1035 [inline] sit_tunnel_xmit+0xa44/0x1b80 net/ipv6/sit.c:1072 __netdev_start_xmit include/linux/netdevice.h:5394 [inline] netdev_start_xmit include/linux/netdevice.h:5403 [inline] xmit_one net/core/dev.c:3889 [inline] dev_hard_start_xmit+0x2df/0x860 net/core/dev.c:3905 __dev_queue_xmit+0x1428/0x3900 net/core/dev.c:4872 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246 ip6tunnel_xmit+0x226/0x6c0 include/net/ip6_tunnel.h:174 ip6_tnl_xmit+0x216d/0x2930 net/ipv6/ip6_tunnel.c:1292 __gre6_xmit+0xa4d/0xd50 net/ipv6/ip6_gre.c:787 ip6gre_xmit_ipv6 net/ipv6/ip6_gre.c:845 [inline] ip6gre_tunnel_xmit+0xc3b/0xf70 net/ipv6/ip6_gre.c:897 __netdev_start_xmit include/linux/netdevice.h:5394 [inline] netdev_start_xmit include/linux/netdevice.h:5403 [inline] xmit_one net/core/dev.c:3889 [inline] dev_hard_start_xmit+0x2df/0x860 net/core/dev.c:3905 sch_direct_xmit+0x251/0x4c0 net/sched/sch_generic.c:372 __dev_xmit_skb net/core/dev.c:4211 [inline] __dev_queue_xmit+0x171e/0x3900 net/core/dev.c:4833 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246 dst_output include/net/dst.h:488 [inline] NF_HOOK include/linux/netfilter.h:318 [inline] ndisc_send_skb+0xd0b/0x1670 net/ipv6/ndisc.c:512 addrconf_rs_timer+0x395/0x6d0 net/ipv6/addrconf.c:4056 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2374 [inline] __run_timer_base+0x6a3/0x9f0 kernel/time/timer.c:2386 run_timer_base kernel/time/timer.c:2395 [inline] run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405 handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626 __do_softirq kernel/softirq.c:660 [inline] run_ktimerd+0x69/0x100 kernel/softirq.c:1155 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160 kthread+0x389/0x470 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 Allocated by task 10052: 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+0x27d/0x6c0 mm/slub.c:5437 _kmalloc_node_noprof include/linux/slab.h:1168 [inline] __get_vm_area_node+0x13f/0x300 mm/vmalloc.c:3215 __vmalloc_node_range_noprof+0x36a/0x1750 mm/vmalloc.c:4022 __vmalloc_node_noprof mm/vmalloc.c:4123 [inline] vmalloc_noprof+0xb2/0xe0 mm/vmalloc.c:4158 bpf_prog_calc_tag+0x4c/0x370 kernel/bpf/core.c:307 check_and_resolve_insns+0xbd/0x2510 kernel/bpf/verifier.c:18084 bpf_check+0x12bf/0x51d0 kernel/bpf/verifier.c:19694 bpf_prog_load+0x1406/0x1a10 kernel/bpf/syscall.c:3128 __sys_bpf+0xd0b/0xd90 kernel/bpf/syscall.c:6350 __do_sys_bpf kernel/bpf/syscall.c:6469 [inline] __se_sys_bpf kernel/bpf/syscall.c:6466 [inline] __x64_sys_bpf+0xba/0xd0 kernel/bpf/syscall.c:6466 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 10052: 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:2700 [inline] slab_free mm/slub.c:6284 [inline] kfree+0x1c5/0x6c0 mm/slub.c:6599 bpf_prog_calc_tag+0x315/0x370 kernel/bpf/core.c:334 check_and_resolve_insns+0xbd/0x2510 kernel/bpf/verifier.c:18084 bpf_check+0x12bf/0x51d0 kernel/bpf/verifier.c:19694 bpf_prog_load+0x1406/0x1a10 kernel/bpf/syscall.c:3128 __sys_bpf+0xd0b/0xd90 kernel/bpf/syscall.c:6350 __do_sys_bpf kernel/bpf/syscall.c:6469 [inline] __se_sys_bpf kernel/bpf/syscall.c:6466 [inline] __x64_sys_bpf+0xba/0xd0 kernel/bpf/syscall.c:6466 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88805f5cd500 which belongs to the cache kmalloc-96 of size 96 The buggy address is located 16 bytes inside of freed 96-byte region [ffff88805f5cd500, ffff88805f5cd560) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88805f5cdd00 pfn:0x5f5cd flags: 0x80000000000200(workingset|node=0|zone=1) page_type: f5(slab) raw: 0080000000000200 ffff88813fe20280 ffffea00009c7810 ffffea000130be50 raw: ffff88805f5cdd00 0000000800200004 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 10, tgid 10 (kworker/0:1), ts 109626662632, free_ts 109611667027 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1866 prep_new_page mm/page_alloc.c:1874 [inline] get_page_from_freelist+0x265c/0x26e0 mm/page_alloc.c:3953 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5296 alloc_slab_page mm/slub.c:3289 [inline] allocate_slab+0x74/0x5e0 mm/slub.c:3404 new_slab mm/slub.c:3447 [inline] refill_objects+0x33c/0x3d0 mm/slub.c:7226 refill_sheaf mm/slub.c:2827 [inline] __pcs_replace_empty_main+0x373/0x720 mm/slub.c:4665 alloc_from_pcs mm/slub.c:4763 [inline] slab_alloc_node mm/slub.c:4897 [inline] __kmalloc_cache_noprof+0x44e/0x690 mm/slub.c:5420 _kmalloc_noprof include/linux/slab.h:967 [inline] _kzalloc_noprof include/linux/slab.h:1284 [inline] nsim_fib6_rt_create drivers/net/netdevsim/fib.c:547 [inline] nsim_fib6_rt_insert drivers/net/netdevsim/fib.c:752 [inline] nsim_fib6_event drivers/net/netdevsim/fib.c:856 [inline] nsim_fib_event+0xf36/0xa390 drivers/net/netdevsim/fib.c:889 nsim_fib_event_work+0x26e/0x3e0 drivers/net/netdevsim/fib.c:1493 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x389/0x470 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 4981 tgid 4981 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1413 [inline] __free_frozen_pages+0x10af/0x1190 mm/page_alloc.c:2957 __slab_free+0x252/0x2a0 mm/slub.c:5646 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:4583 [inline] slab_alloc_node mm/slub.c:4912 [inline] __kmalloc_cache_noprof+0x338/0x690 mm/slub.c:5420 _kmalloc_noprof include/linux/slab.h:967 [inline] _kzalloc_noprof include/linux/slab.h:1284 [inline] kernfs_fop_open+0x39a/0xcb0 fs/kernfs/file.c:641 do_dentry_open+0x83d/0x13e0 fs/open.c:947 vfs_open+0x3b/0x350 fs/open.c:1052 do_open fs/namei.c:4688 [inline] path_openat+0x2eea/0x3960 fs/namei.c:4847 do_file_open+0x23e/0x4a0 fs/namei.c:4876 do_sys_openat2+0x115/0x200 fs/open.c:1344 do_sys_open fs/open.c:1350 [inline] __do_sys_openat fs/open.c:1366 [inline] __se_sys_openat fs/open.c:1361 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1361 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff88805f5cd400: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff88805f5cd480: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >ffff88805f5cd500: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ^ ffff88805f5cd580: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc ffff88805f5cd600: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ================================================================== --- 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