> On Sep 9, 2024, at 02:23, syzbot <syzbot+2dab93857ee95f2eeb08@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 88fac17500f4 Merge tag 'fuse-fixes-6.11-rc7' of git://git... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13291d97980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=660f6eb11f9c7dc5 > dashboard link: https://syzkaller.appspot.com/bug?extid=2dab93857ee95f2eeb08 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/6dfa1c637f53/disk-88fac175.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/7a322b491698/vmlinux-88fac175.xz > kernel image: https://storage.googleapis.com/syzbot-assets/edc9184a3a97/bzImage-88fac175.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+2dab93857ee95f2eeb08@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: slab-use-after-free in __vma_shareable_lock include/linux/hugetlb.h:1278 [inline] This is accessing vma structure. > BUG: KASAN: slab-use-after-free in hugetlb_vma_unlock_read mm/hugetlb.c:281 [inline] > BUG: KASAN: slab-use-after-free in hugetlb_no_page mm/hugetlb.c:6380 [inline] > BUG: KASAN: slab-use-after-free in hugetlb_fault+0xfaf/0x3770 mm/hugetlb.c:6485 > Read of size 8 at addr ffff88807c17f9d0 by task syz.0.4558/26998 > > CPU: 1 UID: 0 PID: 26998 Comm: syz.0.4558 Not tainted 6.11.0-rc6-syzkaller-00026-g88fac17500f4 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:93 [inline] > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119 > print_address_description mm/kasan/report.c:377 [inline] > print_report+0x169/0x550 mm/kasan/report.c:488 > kasan_report+0x143/0x180 mm/kasan/report.c:601 > __vma_shareable_lock include/linux/hugetlb.h:1278 [inline] > hugetlb_vma_unlock_read mm/hugetlb.c:281 [inline] I think vma is freed before this call of hugetlb_vma_unlock_read() but after hugetlb_vma_lock_read() in hugetlb_fault(). I found a possible scenario to cause this problem. hugetlb_no_page() ret = vmf_anon_prepare() if (vmf->flags & FAULT_FLAG_VMA_LOCK) { if (!mmap_read_trylock(vma->vm_mm)) { vma_end_read(vma); // VMA lock is released, which could be freed before the call of hugetlb_vma_unlock_read(). return VM_FAULT_RETRY; } } if (unlikely(ret)) goto out; out: hugetlb_vma_unlock_read(vma); // UAF of VMA The culprit commit should be 7c43a553792a1 ("hugetlb: allow faults to be handled under the VMA lock"). I will take a closer look at the solution tomorrow. And Cc the author of the above commit, maybe have some comments on this. Muchun, Thanks. > hugetlb_no_page mm/hugetlb.c:6380 [inline] > hugetlb_fault+0xfaf/0x3770 mm/hugetlb.c:6485 > handle_mm_fault+0x1901/0x1bc0 mm/memory.c:5830 > do_user_addr_fault arch/x86/mm/fault.c:1338 [inline] > handle_page_fault arch/x86/mm/fault.c:1481 [inline] > exc_page_fault+0x459/0x8c0 arch/x86/mm/fault.c:1539 > asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 > RIP: 0033:0x7f2b63744998 > Code: fc 89 37 c3 c5 fa 6f 06 c5 fa 6f 4c 16 f0 c5 fa 7f 07 c5 fa 7f 4c 17 f0 c3 66 0f 1f 84 00 00 00 00 00 48 8b 4c 16 f8 48 8b 36 <48> 89 37 48 89 4c 17 f8 c3 c5 fe 6f 54 16 e0 c5 fe 6f 5c 16 c0 c5 > RSP: 002b:00007f2b63a5fb88 EFLAGS: 00010206 > RAX: 00000000200002c0 RBX: 0000000000000004 RCX: 00676e7277682f76 > RDX: 000000000000000b RSI: 7277682f7665642f RDI: 00000000200002c0 > RBP: 00007f2b63937a80 R08: 00007f2b63600000 R09: 0000000000000001 > R10: 0000000000000001 R11: 0000000000000009 R12: 000000000014aa5e > R13: 00007f2b63a5fc90 R14: 0000000000000032 R15: fffffffffffffffe > </TASK> > > Allocated by task 27000: > kasan_save_stack mm/kasan/common.c:47 [inline] > kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 > unpoison_slab_object mm/kasan/common.c:312 [inline] > __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338 > kasan_slab_alloc include/linux/kasan.h:201 [inline] > slab_post_alloc_hook mm/slub.c:3988 [inline] > slab_alloc_node mm/slub.c:4037 [inline] > kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4044 > vm_area_alloc+0x24/0x1d0 kernel/fork.c:471 > mmap_region+0xc3d/0x2090 mm/mmap.c:2944 > do_mmap+0x8f9/0x1010 mm/mmap.c:1468 > vm_mmap_pgoff+0x1dd/0x3d0 mm/util.c:588 > ksys_mmap_pgoff+0x544/0x720 mm/mmap.c:1514 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > Freed by task 26255: > kasan_save_stack mm/kasan/common.c:47 [inline] > kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 > kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579 > poison_slab_object+0xe0/0x150 mm/kasan/common.c:240 > __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256 > kasan_slab_free include/linux/kasan.h:184 [inline] > slab_free_hook mm/slub.c:2252 [inline] > slab_free mm/slub.c:4473 [inline] > kmem_cache_free+0x145/0x350 mm/slub.c:4548 > rcu_do_batch kernel/rcu/tree.c:2569 [inline] > rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2843 VMA structure is freed via rcu, so it is really a UAF problem. > handle_softirqs+0x2c4/0x970 kernel/softirq.c:554 > do_softirq+0x11b/0x1e0 kernel/softirq.c:455 > __local_bh_enable_ip+0x1bb/0x200 kernel/softirq.c:382 > spin_unlock_bh include/linux/spinlock.h:396 [inline] > __fib6_clean_all+0x327/0x4b0 net/ipv6/ip6_fib.c:2277 > rt6_sync_down_dev net/ipv6/route.c:4908 [inline] > rt6_disable_ip+0x164/0x7e0 net/ipv6/route.c:4913 > addrconf_ifdown+0x15d/0x1bd0 net/ipv6/addrconf.c:3856 > addrconf_notify+0x3cb/0x1020 > notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93 > call_netdevice_notifiers_extack net/core/dev.c:2032 [inline] > call_netdevice_notifiers net/core/dev.c:2046 [inline] > dev_close_many+0x33c/0x4c0 net/core/dev.c:1587 > unregister_netdevice_many_notify+0x50b/0x1c40 net/core/dev.c:11327 > unregister_netdevice_many net/core/dev.c:11414 [inline] > default_device_exit_batch+0xa0f/0xa90 net/core/dev.c:11897 > ops_exit_list net/core/net_namespace.c:178 [inline] > cleanup_net+0x89d/0xcc0 net/core/net_namespace.c:640 > process_one_work kernel/workqueue.c:3231 [inline] > process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 > worker_thread+0x86d/0xd10 kernel/workqueue.c:3389 > kthread+0x2f0/0x390 kernel/kthread.c:389 > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > Last potentially related work creation: > kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47 > __kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541 > __call_rcu_common kernel/rcu/tree.c:3106 [inline] > call_rcu+0x167/0xa70 kernel/rcu/tree.c:3210 > remove_vma mm/mmap.c:189 [inline] > remove_mt mm/mmap.c:2415 [inline] > do_vmi_align_munmap+0x155c/0x18c0 mm/mmap.c:2758 > do_vmi_munmap+0x261/0x2f0 mm/mmap.c:2830 > mmap_region+0x72f/0x2090 mm/mmap.c:2881 > do_mmap+0x8f9/0x1010 mm/mmap.c:1468 > vm_mmap_pgoff+0x1dd/0x3d0 mm/util.c:588 > ksys_mmap_pgoff+0x544/0x720 mm/mmap.c:1514 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > The buggy address belongs to the object at ffff88807c17f9b0 > which belongs to the cache vm_area_struct of size 184 > The buggy address is located 32 bytes inside of > freed 184-byte region [ffff88807c17f9b0, ffff88807c17fa68) > > The buggy address belongs to the physical page: > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7c17f > memcg:ffff888028997401 > anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) > page_type: 0xfdffffff(slab) > raw: 00fff00000000000 ffff88801bafdb40 ffffea0001f89e00 000000000000000d > raw: 0000000000000000 0000000000100010 00000001fdffffff ffff888028997401 > page dumped because: kasan: bad access detected > page_owner tracks the page as allocated > page last allocated via order 0, migratetype Unmovable, gfp_mask 0x152cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 26741, tgid 26741 (dhcpcd-run-hook), ts 1341391347767, free_ts 1341166373745 > set_page_owner include/linux/page_owner.h:32 [inline] > post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493 > prep_new_page mm/page_alloc.c:1501 [inline] > get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3439 > __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4695 > __alloc_pages_node_noprof include/linux/gfp.h:269 [inline] > alloc_pages_node_noprof include/linux/gfp.h:296 [inline] > alloc_slab_page+0x5f/0x120 mm/slub.c:2321 > allocate_slab+0x5a/0x2f0 mm/slub.c:2484 > new_slab mm/slub.c:2537 [inline] > ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3723 > __slab_alloc+0x58/0xa0 mm/slub.c:3813 > __slab_alloc_node mm/slub.c:3866 [inline] > slab_alloc_node mm/slub.c:4025 [inline] > kmem_cache_alloc_noprof+0x1c1/0x2a0 mm/slub.c:4044 > vm_area_dup+0x27/0x290 kernel/fork.c:486 > dup_mmap kernel/fork.c:695 [inline] > dup_mm kernel/fork.c:1672 [inline] > copy_mm+0xc7b/0x1f30 kernel/fork.c:1721 > copy_process+0x187a/0x3dc0 kernel/fork.c:2374 > kernel_clone+0x226/0x8f0 kernel/fork.c:2781 > __do_sys_clone kernel/fork.c:2924 [inline] > __se_sys_clone kernel/fork.c:2908 [inline] > __x64_sys_clone+0x258/0x2a0 kernel/fork.c:2908 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > page last free pid 26730 tgid 26718 stack trace: > reset_page_owner include/linux/page_owner.h:25 [inline] > free_pages_prepare mm/page_alloc.c:1094 [inline] > free_unref_page+0xd22/0xea0 mm/page_alloc.c:2612 > __folio_put+0x2c8/0x440 mm/swap.c:128 > migrate_folio_move mm/migrate.c:1330 [inline] > migrate_pages_batch+0x2a76/0x3560 mm/migrate.c:1818 > migrate_pages_sync mm/migrate.c:1884 [inline] > migrate_pages+0x1f59/0x3460 mm/migrate.c:1993 > do_mbind mm/mempolicy.c:1388 [inline] > kernel_mbind mm/mempolicy.c:1531 [inline] > __do_sys_mbind mm/mempolicy.c:1605 [inline] > __se_sys_mbind+0x1490/0x19f0 mm/mempolicy.c:1601 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > Memory state around the buggy address: > ffff88807c17f880: fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00 00 > ffff88807c17f900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc >> ffff88807c17f980: fc fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb > ^ > ffff88807c17fa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc > ffff88807c17fa80: fc fc fc fc fc 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@xxxxxxxxxxxxxxxx. > > 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
