================================================================== BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:814 [inline] BUG: KASAN: use-after-free in enqueue_timer+0xb7/0x300 kernel/time/timer.c:541 Write of size 8 at addr ffff8881d4a0f1c8 by task syz.5.432/2158 CPU: 0 PID: 2158 Comm: syz.5.432 Not tainted 5.4.290-syzkaller-00017-g6b07fcd94a6a #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1d8/0x241 lib/dump_stack.c:118 print_address_description+0x8c/0x600 mm/kasan/report.c:384 __kasan_report+0xf3/0x120 mm/kasan/report.c:516 kasan_report+0x30/0x60 mm/kasan/common.c:653 hlist_add_head include/linux/list.h:814 [inline] enqueue_timer+0xb7/0x300 kernel/time/timer.c:541 __internal_add_timer kernel/time/timer.c:554 [inline] internal_add_timer+0x240/0x430 kernel/time/timer.c:604 __mod_timer+0x6f1/0x13e0 kernel/time/timer.c:1065 call_timer_fn+0x36/0x390 kernel/time/timer.c:1448 expire_timers kernel/time/timer.c:1493 [inline] __run_timers+0x879/0xbe0 kernel/time/timer.c:1817 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1830 __do_softirq+0x23b/0x6b7 kernel/softirq.c:292 invoke_softirq kernel/softirq.c:373 [inline] irq_exit+0x195/0x1c0 kernel/softirq.c:413 exiting_irq arch/x86/include/asm/apic.h:539 [inline] smp_apic_timer_interrupt+0x11a/0x490 arch/x86/kernel/apic/apic.c:1161 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:834 RIP: 0010:arch_atomic_dec_and_test arch/x86/include/asm/atomic.h:125 [inline] RIP: 0010:atomic_dec_and_test include/asm-generic/atomic-instrumented.h:748 [inline] RIP: 0010:page_ref_dec_and_test include/linux/page_ref.h:139 [inline] RIP: 0010:put_page_testzero include/linux/mm.h:699 [inline] RIP: 0010:release_pages+0x228/0xb20 mm/swap.c:802 Code: 31 ff e8 ab f7 e1 ff f6 c3 01 0f 85 e4 07 00 00 e8 3d f4 e1 ff 49 8d 7f 34 be 04 00 00 00 e8 cf b1 11 00 31 db f0 41 ff 4f 34 <41> 0f 94 c6 0f 94 c3 bf 02 00 00 00 89 de e8 25 f6 e1 ff 31 ff 89 RSP: 0018:ffff8881d47bf760 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13 RAX: ffffffff81825601 RBX: 0000000000000000 RCX: ffffffff818256d1 RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffea00076a0d34 RBP: ffff8881d47bf868 R08: dffffc0000000000 R09: fffff94000ed41a7 R10: 0000000000000000 R11: dffffc0000000001 R12: ffff8881d4332010 R13: 0000000000000000 R14: dffffc0000000000 R15: ffffea00076a0d00 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline] tlb_flush_mmu_free mm/mmu_gather.c:189 [inline] tlb_flush_mmu mm/mmu_gather.c:196 [inline] tlb_finish_mmu+0x177/0x320 mm/mmu_gather.c:277 exit_mmap+0x2dc/0x520 mm/mmap.c:3193 __mmput+0x8e/0x2c0 kernel/fork.c:1101 exit_mm kernel/exit.c:538 [inline] do_exit+0xc08/0x2bc0 kernel/exit.c:848 do_group_exit+0x138/0x300 kernel/exit.c:984 get_signal+0xdb1/0x1440 kernel/signal.c:2738 do_signal+0xb0/0x11f0 arch/x86/kernel/signal.c:809 exit_to_usermode_loop+0xc0/0x1a0 arch/x86/entry/common.c:159 prepare_exit_to_usermode+0x199/0x200 arch/x86/entry/common.c:194 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 RIP: 0033:0x7f7f6e26f169 Code: Bad RIP value. RSP: 002b:00007f7f6c8b80e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 00007f7f6e488088 RCX: 00007f7f6e26f169 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f7f6e488088 RBP: 00007f7f6e488080 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7f6e48808c R13: 0000000000000000 R14: 00007fff06a111a0 R15: 00007fff06a11288 The buggy address belongs to the page: page:ffffea00075283c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x8000000000000000() raw: 8000000000000000 0000000000000000 ffffea00075283c8 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as freed page last allocated via order 2, migratetype Unmovable, gfp_mask 0x146dc0(GFP_USER|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_COMP|__GFP_ZERO) set_page_owner include/linux/page_owner.h:31 [inline] post_alloc_hook mm/page_alloc.c:2165 [inline] prep_new_page+0x18f/0x370 mm/page_alloc.c:2171 get_page_from_freelist+0x2d13/0x2d90 mm/page_alloc.c:3794 __alloc_pages_nodemask+0x393/0x840 mm/page_alloc.c:4893 __alloc_pages include/linux/gfp.h:503 [inline] __alloc_pages_node include/linux/gfp.h:516 [inline] alloc_pages_node include/linux/gfp.h:530 [inline] kmalloc_order mm/slab_common.c:1342 [inline] kmalloc_order_trace+0x2a/0x100 mm/slab_common.c:1358 __kmalloc_node include/linux/slab.h:422 [inline] kmalloc_node include/linux/slab.h:599 [inline] kvmalloc_node+0x7e/0xf0 mm/util.c:596 kvmalloc include/linux/mm.h:761 [inline] kvzalloc include/linux/mm.h:769 [inline] alloc_netdev_mqs+0x85/0xc70 net/core/dev.c:9629 tun_set_iff+0x51f/0xdc0 drivers/net/tun.c:2893 __tun_chr_ioctl+0x8a9/0x1d00 drivers/net/tun.c:3187 do_vfs_ioctl+0x742/0x1720 fs/ioctl.c:47 ksys_ioctl fs/ioctl.c:742 [inline] __do_sys_ioctl fs/ioctl.c:749 [inline] __se_sys_ioctl fs/ioctl.c:747 [inline] __x64_sys_ioctl+0xd4/0x110 fs/ioctl.c:747 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1176 [inline] __free_pages_ok+0x847/0x950 mm/page_alloc.c:1438 free_the_page mm/page_alloc.c:4955 [inline] __free_pages+0x91/0x140 mm/page_alloc.c:4961 device_release+0x6b/0x190 drivers/base/core.c:1776 kobject_cleanup lib/kobject.c:716 [inline] kobject_release lib/kobject.c:747 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1e6/0x2f0 lib/kobject.c:764 tun_set_iff+0x870/0xdc0 drivers/net/tun.c:2924 __tun_chr_ioctl+0x8a9/0x1d00 drivers/net/tun.c:3187 do_vfs_ioctl+0x742/0x1720 fs/ioctl.c:47 ksys_ioctl fs/ioctl.c:742 [inline] __do_sys_ioctl fs/ioctl.c:749 [inline] __se_sys_ioctl fs/ioctl.c:747 [inline] __x64_sys_ioctl+0xd4/0x110 fs/ioctl.c:747 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x5c/0xc1 Memory state around the buggy address: ffff8881d4a0f080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff8881d4a0f100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff8881d4a0f180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff8881d4a0f200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff8881d4a0f280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== ---------------- Code disassembly (best guess): 0: 31 ff xor %edi,%edi 2: e8 ab f7 e1 ff call 0xffe1f7b2 7: f6 c3 01 test $0x1,%bl a: 0f 85 e4 07 00 00 jne 0x7f4 10: e8 3d f4 e1 ff call 0xffe1f452 15: 49 8d 7f 34 lea 0x34(%r15),%rdi 19: be 04 00 00 00 mov $0x4,%esi 1e: e8 cf b1 11 00 call 0x11b1f2 23: 31 db xor %ebx,%ebx 25: f0 41 ff 4f 34 lock decl 0x34(%r15) * 2a: 41 0f 94 c6 sete %r14b <-- trapping instruction 2e: 0f 94 c3 sete %bl 31: bf 02 00 00 00 mov $0x2,%edi 36: 89 de mov %ebx,%esi 38: e8 25 f6 e1 ff call 0xffe1f662 3d: 31 ff xor %edi,%edi 3f: 89 .byte 0x89