From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f79.google.com (mail-oo1-f79.google.com [209.85.161.79]) (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 5F00F3876C7 for ; Mon, 9 Feb 2026 18:35:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.79 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770662134; cv=none; b=svBzS8WbI2EvVV3G8ub8oJhQVDK9FUGzwSUsHn27xaTAZaHUpiwKBmImHW0DaUv5OnYmNHI9GZBmEduBXg0X+BN1Kdg8+9fa405dmWHheLyzbhXsCePV4O081Js+/JQfu5Dlq+K3iU3Zim6dZZFTjlncVLU2TD3LavZtVM3uU+g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770662134; c=relaxed/simple; bh=LdVtwpRxDCnJM5F0Vu1ghRkmhsv/wKAya9T/ZdcmWxk=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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006d021491bc7-66d0c854dfemr5447774eaf.57.1770662133305; Mon, 09 Feb 2026 10:35:33 -0800 (PST) Date: Mon, 09 Feb 2026 10:35:33 -0800 In-Reply-To: <00000000000086d83c0615ba6f9a@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <698a28f5.a00a0220.34fa92.004a.GAE@google.com> Subject: Re: [syzbot] [net?] KMSAN: uninit-value in __schedule (5) From: syzbot To: bp@alien8.de, dave.hansen@linux.intel.com, davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, horms@kernel.org, hpa@zytor.com, kuba@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, x86@kernel.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 05f7e89ab973 Linux 6.19 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17daf65a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=df890e720d1bb80 dashboard link: https://syzkaller.appspot.com/bug?extid=28bdcfc1dab2ffa279a5 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1029533a580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/ea9f39c5175d/disk-05f7e89a.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/734edeebfa32/vmlinux-05f7e89a.xz kernel image: https://storage.googleapis.com/syzbot-assets/a2cb36d849f0/bzImage-05f7e89a.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+28bdcfc1dab2ffa279a5@syzkaller.appspotmail.com ================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] BUG: KASAN: slab-use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] BUG: KASAN: slab-use-after-free in membarrier_switch_mm kernel/sched/sched.h:3666 [inline] BUG: KASAN: slab-use-after-free in context_switch kernel/sched/core.c:5230 [inline] BUG: KASAN: slab-use-after-free in __schedule+0xc56/0x5fa0 kernel/sched/core.c:6867 Read of size 4 at addr ffff88801db4e2c0 by task kworker/u8:1/13 CPU: 0 UID: 0 PID: 13 Comm: kworker/u8:1 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 Workqueue: ipv6_addrconf addrconf_dad_work Call Trace: __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+0x156/0x4c9 mm/kasan/report.c:482 kasan_report+0xdf/0x1a0 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:186 [inline] kasan_check_range+0x10f/0x1e0 mm/kasan/generic.c:200 instrument_atomic_read include/linux/instrumented.h:68 [inline] atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] membarrier_switch_mm kernel/sched/sched.h:3666 [inline] context_switch kernel/sched/core.c:5230 [inline] __schedule+0xc56/0x5fa0 kernel/sched/core.c:6867 __schedule_loop kernel/sched/core.c:6949 [inline] schedule+0xdd/0x390 kernel/sched/core.c:6964 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7021 __mutex_lock_common kernel/locking/mutex.c:692 [inline] __mutex_lock+0xc9a/0x1b90 kernel/locking/mutex.c:776 rtnl_net_lock include/linux/rtnetlink.h:130 [inline] addrconf_dad_work+0x11f/0x1360 net/ipv6/addrconf.c:4194 process_one_work+0x9c2/0x1840 kernel/workqueue.c:3257 process_scheduled_works kernel/workqueue.c:3340 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3421 kthread+0x3b3/0x730 kernel/kthread.c:463 ret_from_fork+0x754/0xaf0 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Allocated by task 5942: kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4953 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x2ad/0x780 mm/slub.c:5270 dup_mm kernel/fork.c:1519 [inline] copy_mm kernel/fork.c:1581 [inline] copy_process+0x73df/0x7890 kernel/fork.c:2221 kernel_clone+0xfc/0x930 kernel/fork.c:2651 __do_sys_clone+0xd9/0x120 kernel/fork.c:2792 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 6090: 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:2540 [inline] slab_free mm/slub.c:6674 [inline] kmem_cache_free+0x143/0x720 mm/slub.c:6789 mmdrop include/linux/sched/mm.h:55 [inline] mmdrop_sched include/linux/sched/mm.h:83 [inline] mmdrop_lazy_tlb_sched include/linux/sched/mm.h:110 [inline] finish_task_switch.isra.0+0x76e/0xb70 kernel/sched/core.c:5143 context_switch kernel/sched/core.c:5263 [inline] __schedule+0xfee/0x5fa0 kernel/sched/core.c:6867 preempt_schedule_common+0x42/0xc0 kernel/sched/core.c:7051 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] _raw_spin_unlock_irqrestore+0x61/0x80 kernel/locking/spinlock.c:194 anon_pipe_write+0xdaa/0x1d40 fs/pipe.c:596 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6ac/0x1070 fs/read_write.c:686 ksys_write+0x1f8/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88801db4e200 which belongs to the cache mm_struct of size 2968 The buggy address is located 192 bytes inside of freed 2968-byte region [ffff88801db4e200, ffff88801db4ed98) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1db48 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 memcg:ffff888031ddb901 flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000040 ffff88813ff30b40 dead000000000100 dead000000000122 raw: 0000000000000000 00000000800a000a 00000000f5000000 ffff888031ddb901 head: 00fff00000000040 ffff88813ff30b40 dead000000000100 dead000000000122 head: 0000000000000000 00000000800a000a 00000000f5000000 ffff888031ddb901 head: 00fff00000000003 ffffea000076d201 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 5202, tgid 5202 (udevd), ts 49764882375, free_ts 49738398245 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x1e1/0x250 mm/page_alloc.c:1884 prep_new_page mm/page_alloc.c:1892 [inline] get_page_from_freelist+0xe3d/0x2e10 mm/page_alloc.c:3945 __alloc_frozen_pages_noprof+0x26c/0x2410 mm/page_alloc.c:5240 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2486 alloc_slab_page mm/slub.c:3075 [inline] allocate_slab mm/slub.c:3248 [inline] new_slab+0x2c4/0x440 mm/slub.c:3302 ___slab_alloc+0xda3/0x1ca0 mm/slub.c:4656 __slab_alloc.isra.0+0x63/0x110 mm/slub.c:4779 __slab_alloc_node mm/slub.c:4855 [inline] slab_alloc_node mm/slub.c:5251 [inline] kmem_cache_alloc_noprof+0x4ec/0x780 mm/slub.c:5270 dup_mm kernel/fork.c:1519 [inline] copy_mm kernel/fork.c:1581 [inline] copy_process+0x73df/0x7890 kernel/fork.c:2221 kernel_clone+0xfc/0x930 kernel/fork.c:2651 __do_sys_clone+0xd9/0x120 kernel/fork.c:2792 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f page last free pid 5349 tgid 5349 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1433 [inline] __free_frozen_pages+0x822/0x1130 mm/page_alloc.c:2973 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x47/0xe0 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:4953 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x2ad/0x780 mm/slub.c:5270 vm_area_dup+0x27/0x8e0 mm/vma_init.c:123 __split_vma+0x18c/0xe30 mm/vma.c:513 vms_gather_munmap_vmas+0x3aa/0x1320 mm/vma.c:1423 __mmap_setup mm/vma.c:2405 [inline] __mmap_region+0x46e/0x2820 mm/vma.c:2734 mmap_region+0x180/0x3e0 mm/vma.c:2830 do_mmap+0xc63/0x12f0 mm/mmap.c:558 vm_mmap_pgoff+0x29e/0x470 mm/util.c:581 ksys_mmap_pgoff+0x328/0x5b0 mm/mmap.c:604 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline] __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff88801db4e180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88801db4e200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88801db4e280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88801db4e300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88801db4e380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.