================================================================== BUG: KASAN: slab-use-after-free in kvm_gmem_release+0x176/0x440 virt/kvm/guest_memfd.c:353 Write of size 8 at addr ffff888076c3a908 by task syz.0.17/5987 CPU: 1 UID: 0 PID: 5987 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x240 mm/kasan/report.c:482 kasan_report+0x118/0x150 mm/kasan/report.c:595 kvm_gmem_release+0x176/0x440 virt/kvm/guest_memfd.c:353 __fput+0x44c/0xa70 fs/file_table.c:468 task_work_run+0x1d4/0x260 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe89eb8efc9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc05374288 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007fe89ede7da0 RCX: 00007fe89eb8efc9 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007fe89ede7da0 R08: 0000000000000000 R09: 000000040537457f R10: 00007fe89ede7cb0 R11: 0000000000000246 R12: 000000000001915f R13: 00007ffc05374380 R14: ffffffffffffffff R15: 00007ffc053743a0 Allocated by task 5988: kasan_save_stack mm/kasan/common.c:56 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:77 poison_kmalloc_redzone mm/kasan/common.c:397 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414 kasan_kmalloc include/linux/kasan.h:262 [inline] __kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5758 kmalloc_noprof include/linux/slab.h:957 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] kvm_set_memory_region+0x747/0xb90 virt/kvm/kvm_main.c:2104 kvm_vm_ioctl_set_memory_region+0x6f/0xd0 virt/kvm/kvm_main.c:2154 kvm_vm_ioctl+0x957/0xc60 virt/kvm/kvm_main.c:5201 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+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5988: kasan_save_stack mm/kasan/common.c:56 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:77 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:252 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284 kasan_slab_free include/linux/kasan.h:234 [inline] slab_free_hook mm/slub.c:2533 [inline] slab_free mm/slub.c:6622 [inline] kfree+0x19a/0x6d0 mm/slub.c:6829 kvm_set_memory_region+0x9c4/0xb90 virt/kvm/kvm_main.c:2130 kvm_vm_ioctl_set_memory_region+0x6f/0xd0 virt/kvm/kvm_main.c:2154 kvm_vm_ioctl+0x957/0xc60 virt/kvm/kvm_main.c:5201 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+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff888076c3a800 which belongs to the cache kmalloc-cg-512 of size 512 The buggy address is located 264 bytes inside of freed 512-byte region [ffff888076c3a800, ffff888076c3aa00) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x76c38 head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 memcg:ffff888078e60a01 flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff) page_type: f5(slab) raw: 00fff00000000040 ffff88813fe30140 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000100010 00000000f5000000 ffff888078e60a01 head: 00fff00000000040 ffff88813fe30140 dead000000000122 0000000000000000 head: 0000000000000000 0000000000100010 00000000f5000000 ffff888078e60a01 head: 00fff00000000002 ffffea0001db0e01 00000000ffffffff 00000000ffffffff head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 50, tgid 50 (kworker/u8:3), ts 101888316348, free_ts 97186106390 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851 prep_new_page mm/page_alloc.c:1859 [inline] get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3920 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5214 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2418 alloc_slab_page mm/slub.c:3049 [inline] allocate_slab+0x96/0x3a0 mm/slub.c:3222 new_slab mm/slub.c:3276 [inline] ___slab_alloc+0xe94/0x18a0 mm/slub.c:4646 __slab_alloc+0x65/0x100 mm/slub.c:4765 __slab_alloc_node mm/slub.c:4841 [inline] slab_alloc_node mm/slub.c:5263 [inline] __kmalloc_cache_noprof+0x41e/0x700 mm/slub.c:5753 kmalloc_noprof include/linux/slab.h:957 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] ipv6_add_addr+0x530/0x1090 net/ipv6/addrconf.c:1120 addrconf_add_linklocal+0x28c/0x6c0 net/ipv6/addrconf.c:3311 addrconf_addr_gen+0x490/0x580 net/ipv6/addrconf.c:3442 addrconf_init_auto_addrs+0x62d/0xa30 net/ipv6/addrconf.c:-1 addrconf_notify+0xacc/0x1010 net/ipv6/addrconf.c:3740 notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85 netif_state_change+0x284/0x3a0 net/core/dev.c:1583 linkwatch_do_dev+0x124/0x180 net/core/link_watch.c:186 page last free pid 5928 tgid 5928 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1395 [inline] __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2948 vfree+0x25a/0x400 mm/vmalloc.c:3467 kcov_put kernel/kcov.c:439 [inline] kcov_close+0x28/0x50 kernel/kcov.c:535 __fput+0x44c/0xa70 fs/file_table.c:468 task_work_run+0x1d4/0x260 kernel/task_work.c:227 exit_task_work include/linux/task_work.h:40 [inline] do_exit+0x6b5/0x2300 kernel/exit.c:966 do_group_exit+0x21c/0x2d0 kernel/exit.c:1107 get_signal+0x1285/0x1340 kernel/signal.c:3034 arch_do_signal_or_restart+0xa0/0x790 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop+0x72/0x130 kernel/entry/common.c:40 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff888076c3a800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888076c3a880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888076c3a900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888076c3a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888076c3aa00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================