[Syzkaller & bisect] There is KASAN: slab-use-after-free Read in __nf_unregister_net_hook in v6.12-rc1

["Lai, Yi" <yi1.lai@linux.intel.com>]

Hi Eric,

Greetings!

I used Syzkaller and found that there is KASAN: slab-use-after-free Read in __nf_unregister_net_hook in v6.12-rc1

After bisection and the first bad commit is:
"
78c3253f27e5 net: use synchronize_rcu_expedited in cleanup_net()
"

All detailed into can be found at:
https://github.com/laifryiee/syzkaller_logs/tree/main/241001_170248___nf_unregister_net_hook
Syzkaller repro code:
https://github.com/laifryiee/syzkaller_logs/tree/main/241001_170248___nf_unregister_net_hook/repro.c
Syzkaller repro syscall steps:
https://github.com/laifryiee/syzkaller_logs/tree/main/241001_170248___nf_unregister_net_hook/repro.prog
Syzkaller report:
https://github.com/laifryiee/syzkaller_logs/tree/main/241001_170248___nf_unregister_net_hook/repro.report
Kconfig(make olddefconfig):
https://github.com/laifryiee/syzkaller_logs/tree/main/241001_170248___nf_unregister_net_hook/kconfig_origin
Bisect info:
https://github.com/laifryiee/syzkaller_logs/tree/main/241001_170248___nf_unregister_net_hook/bisect_info.log
bzImage:
https://github.com/laifryiee/syzkaller_logs/raw/refs/heads/main/241001_170248___nf_unregister_net_hook/bzImage_9852d85ec9d492ebef56dc5f229416c925758edc
Issue dmesg:
https://github.com/laifryiee/syzkaller_logs/blob/main/241001_170248___nf_unregister_net_hook/9852d85ec9d492ebef56dc5f229416c925758edc_dmesg.log

"
[   16.910304] ==================================================================
[   16.910757] BUG: KASAN: slab-use-after-free in __nf_unregister_net_hook+0x640/0x6b0
[   16.911156] Read of size 8 at addr ffff8880106fe400 by task repro/725
[   16.911529]
[   16.911674] CPU: 1 UID: 0 PID: 725 Comm: repro Not tainted 6.12.0-rc1-9852d85ec9d4+ #1
[   16.912338] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[   16.913460] Call Trace:
[   16.913859]  <TASK>
[   16.913983]  dump_stack_lvl+0xea/0x150
[   16.914262]  print_report+0xce/0x610
[   16.914585]  ? __nf_unregister_net_hook+0x640/0x6b0
[   16.914845]  ? kasan_complete_mode_report_info+0x80/0x200
[   16.915133]  ? __nf_unregister_net_hook+0x640/0x6b0
[   16.915497]  kasan_report+0xcc/0x110
[   16.915687]  ? __nf_unregister_net_hook+0x640/0x6b0
[   16.916082]  ? __pfx_bpf_link_release+0x10/0x10
[   16.916398]  __asan_report_load8_noabort+0x18/0x20
[   16.916655]  __nf_unregister_net_hook+0x640/0x6b0
[   16.916895]  ? __pfx_bpf_link_release+0x10/0x10
[   16.917177]  ? __pfx_bpf_link_release+0x10/0x10
[   16.917467]  nf_unregister_net_hook+0xea/0x140
[   16.917770]  bpf_nf_link_release+0xda/0x1e0
[   16.917983]  bpf_link_free+0x139/0x2d0
[   16.918187]  bpf_link_release+0x68/0x80
[   16.918397]  __fput+0x414/0xb60
[   16.918603]  ____fput+0x22/0x30
[   16.918777]  task_work_run+0x19c/0x2b0
[   16.919006]  ? __pfx_task_work_run+0x10/0x10
[   16.919235]  ? free_nsproxy+0x344/0x470
[   16.919448]  ? switch_task_namespaces+0xf9/0x110
[   16.919711]  do_exit+0xb19/0x2a30
[   16.919913]  ? audit_log_end+0x156/0x2c0
[   16.920202]  ? __pfx_do_exit+0x10/0x10
[   16.920419]  ? audit_seccomp+0x1b2/0x220
[   16.920656]  ? audit_seccomp+0x1b9/0x220
[   16.920872]  __secure_computing+0x2f5/0x350
[   16.921109]  syscall_trace_enter+0x9b/0x230
[   16.921354]  do_syscall_64+0x115/0x140
[   16.921551]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[   16.921816] RIP: 0033:0x7f2464518a4d
[   16.922038] Code: Unable to access opcode bytes at 0x7f2464518a23.
[   16.922363] RSP: 002b:00007ffe02122928 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
[   16.922759] RAX: ffffffffffffffda RBX: 00007f24645f69e0 RCX: 00007f2464518a4d
[   16.923163] RDX: 00000000000000e7 RSI: ffffffffffffff80 RDI: 0000000000000000
[   16.923583] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000020
[   16.923965] R10: 00007ffe021227d0 R11: 0000000000000246 R12: 00007f24645f69e0
[   16.924353] R13: 00007f24645fbf00 R14: 0000000000000001 R15: 00007f24645fbee8
[   16.924750]  </TASK>
[   16.924870]
[   16.924962] Allocated by task 725:
[   16.925153]  kasan_save_stack+0x2c/0x60
[   16.925387]  kasan_save_track+0x18/0x40
[   16.925607]  kasan_save_alloc_info+0x3c/0x50
[   16.925853]  __kasan_slab_alloc+0x62/0x80
[   16.926065]  kmem_cache_alloc_noprof+0x114/0x370
[   16.926334]  copy_net_ns+0xf0/0x6e0
[   16.926520]  create_new_namespaces+0x403/0xb40
[   16.926769]  unshare_nsproxy_namespaces+0xca/0x200
[   16.927038]  ksys_unshare+0x424/0xa10
[   16.927242]  __x64_sys_unshare+0x3a/0x50
[   16.927451]  x64_sys_call+0xcf1/0x20d0
[   16.927670]  do_syscall_64+0x6d/0x140
[   16.927888]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[   16.928148]
[   16.928243] Freed by task 51:
[   16.928414]  kasan_save_stack+0x2c/0x60
[   16.928631]  kasan_save_track+0x18/0x40
[   16.928841]  kasan_save_free_info+0x3f/0x60
[   16.929073]  __kasan_slab_free+0x3d/0x60
[   16.929308]  kmem_cache_free+0x1aa/0x550
[   16.929529]  cleanup_net+0x8af/0xae0
[   16.929745]  process_one_work+0x92e/0x1b50
[   16.929981]  worker_thread+0x68d/0xe90
[   16.930204]  kthread+0x35a/0x470
[   16.930424]  ret_from_fork+0x56/0x90
[   16.930626]  ret_from_fork_asm+0x1a/0x30
[   16.930843]
[   16.930935] The buggy address belongs to the object at ffff8880106fd400
[   16.930935]  which belongs to the cache net_namespace of size 6912
[   16.931597] The buggy address is located 4096 bytes inside of
[   16.931597]  freed 6912-byte region [ffff8880106fd400, ffff8880106fef00)
[   16.932280]
[   16.932430] The buggy address belongs to the physical page:
[   16.932757] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106f8
[   16.933195] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[   16.933592] memcg:ffff88801157d281
[   16.933783] flags: 0xfffffc0000040(head|node=0|zone=1|lastcpupid=0x1fffff)
[   16.934155] page_type: f5(slab)
[   16.934329] raw: 000fffffc0000040 ffff88800d71cdc0 dead000000000122 0000000000000000
[   16.934782] raw: 0000000000000000 0000000080040004 00000001f5000000 ffff88801157d281
[   16.935209] head: 000fffffc0000040 ffff88800d71cdc0 dead000000000122 0000000000000000
[   16.935610] head: 0000000000000000 0000000080040004 00000001f5000000 ffff88801157d281
[   16.936038] head: 000fffffc0000003 ffffea000041be01 ffffffffffffffff 0000000000000000
[   16.936507] head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
[   16.936913] page dumped because: kasan: bad access detected
[   16.937285]
[   16.937398] Memory state around the buggy address:
[   16.937698]  ffff8880106fe300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[   16.938149]  ffff8880106fe380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[   16.938634] >ffff8880106fe400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[   16.939010]                    ^
"

I hope you find it useful.

Regards,
Yi Lai

---

If you don't need the following environment to reproduce the problem or if you
already have one reproduced environment, please ignore the following information.

How to reproduce:
git clone https://gitlab.com/xupengfe/repro_vm_env.git
cd repro_vm_env
tar -xvf repro_vm_env.tar.gz
cd repro_vm_env; ./start3.sh  // it needs qemu-system-x86_64 and I used v7.1.0
  // start3.sh will load bzImage_2241ab53cbb5cdb08a6b2d4688feb13971058f65 v6.2-rc5 kernel
  // You could change the bzImage_xxx as you want
  // Maybe you need to remove line "-drive if=pflash,format=raw,readonly=on,file=./OVMF_CODE.fd \" for different qemu version
You could use below command to log in, there is no password for root.
ssh -p 10023 root@localhost

After login vm(virtual machine) successfully, you could transfer reproduced
binary to the vm by below way, and reproduce the problem in vm:
gcc -pthread -o repro repro.c
scp -P 10023 repro root@localhost:/root/

Get the bzImage for target kernel:
Please use target kconfig and copy it to kernel_src/.config
make olddefconfig
make -jx bzImage           //x should equal or less than cpu num your pc has

Fill the bzImage file into above start3.sh to load the target kernel in vm.


Tips:
If you already have qemu-system-x86_64, please ignore below info.
If you want to install qemu v7.1.0 version:
git clone https://github.com/qemu/qemu.git
cd qemu
git checkout -f v7.1.0
mkdir build
cd build
yum install -y ninja-build.x86_64
yum -y install libslirp-devel.x86_64
../configure --target-list=x86_64-softmmu --enable-kvm --enable-vnc --enable-gtk --enable-sdl --enable-usb-redir --enable-slirp
make
make install