Date:   Thu, 9 Jun 2022 09:54:24 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     <joannelkoong@...il.com>
CC:     <andrii@...nel.org>, <ast@...nel.org>, <bpf@...r.kernel.org>,
        <daniel@...earbox.net>, <davem@...emloft.net>,
        <dsahern@...nel.org>, <edumazet@...gle.com>,
        <john.fastabend@...il.com>, <kafai@...com>, <kpsingh@...nel.org>,
        <kuba@...nel.org>, <kuniyu@...zon.co.jp>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <pabeni@...hat.com>, <songliubraving@...com>,
        <syzbot+98fd2d1422063b0f8c44@...kaller.appspotmail.com>,
        <syzkaller-bugs@...glegroups.com>, <yhs@...com>,
        <yoshfuji@...ux-ipv6.org>
Subject: Re: [syzbot] KASAN: use-after-free Read in inet_bind2_bucket_find

From:   Joanne Koong <joannelkoong@...il.com>
Date:   Wed, 8 Jun 2022 22:23:14 -0700
> On Tue, Jun 7, 2022 at 1:20 PM Joanne Koong <joannelkoong@...il.com> wrote:
>>
>> On Tue, Jun 7, 2022 at 10:44 AM syzbot
>> <syzbot+98fd2d1422063b0f8c44@...kaller.appspotmail.com> wrote:
>>>
>>> Hello,
>>>
>>> syzbot found the following issue on:
>>>
>>> HEAD commit:    664a393a2663 Merge tag 'input-for-v5.19-rc0' of git://git...
>>> git tree:       upstream
>>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=10c9bf5bf00000
>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=9b19cdd2d45cc221
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=98fd2d1422063b0f8c44
>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=154a123df00000
>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13b9d8cdf00000
>>>
>>> The issue was bisected to:
>>>
>>> commit d5a42de8bdbe25081f07b801d8b35f4d75a791f4
>>> Author: Joanne Koong <joannelkoong@...il.com>
>>> Date:   Fri May 20 00:18:33 2022 +0000
>>>
>>>     net: Add a second bind table hashed by port and address
>>>
>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15c72eedf00000
>>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=17c72eedf00000
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=13c72eedf00000
>>>
>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>> Reported-by: syzbot+98fd2d1422063b0f8c44@...kaller.appspotmail.com
>>> Fixes: d5a42de8bdbe ("net: Add a second bind table hashed by port and address")
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in read_pnet include/net/net_namespace.h:361 [inline]
>>> BUG: KASAN: use-after-free in ib2_net include/net/inet_hashtables.h:116 [inline]
>>> BUG: KASAN: use-after-free in check_bind2_bucket_match net/ipv4/inet_hashtables.c:765 [inline]
>>> BUG: KASAN: use-after-free in inet_bind2_bucket_find+0x562/0x620 net/ipv4/inet_hashtables.c:819
>>> Read of size 8 at addr ffff888020cbc980 by task syz-executor537/3958
>>>
>>> CPU: 0 PID: 3958 Comm: syz-executor537 Not tainted 5.18.0-syzkaller-11080-g664a393a2663 #0
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>>> Call Trace:
>>>  <TASK>
>>>  __dump_stack lib/dump_stack.c:88 [inline]
>>>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>>>  print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
>>>  print_report mm/kasan/report.c:429 [inline]
>>>  kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
>>>  read_pnet include/net/net_namespace.h:361 [inline]
>>>  ib2_net include/net/inet_hashtables.h:116 [inline]
>>>  check_bind2_bucket_match net/ipv4/inet_hashtables.c:765 [inline]
>>>  inet_bind2_bucket_find+0x562/0x620 net/ipv4/inet_hashtables.c:819
>>>  __inet_hash_connect+0xaaa/0x1450 net/ipv4/inet_hashtables.c:949
>>>  dccp_v4_connect+0xc5c/0x16f0 net/dccp/ipv4.c:108
>>>  __inet_stream_connect+0x8cf/0xed0 net/ipv4/af_inet.c:660
>>>  inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:724
>>>  __sys_connect_file+0x14f/0x190 net/socket.c:1979
>>>  io_connect+0x15f/0x690 fs/io_uring.c:6724
>>>  io_issue_sqe+0x40c6/0xa9c0 fs/io_uring.c:8351
>>>  io_queue_sqe fs/io_uring.c:8706 [inline]
>>>  io_req_task_submit+0xce/0x400 fs/io_uring.c:3066
>>>  handle_tw_list fs/io_uring.c:2938 [inline]
>>>  tctx_task_work+0x16a/0xe10 fs/io_uring.c:2967
>>>  task_work_run+0xdd/0x1a0 kernel/task_work.c:177
>>>  ptrace_notify+0x114/0x140 kernel/signal.c:2372
>>>  ptrace_report_syscall include/linux/ptrace.h:427 [inline]
>>>  ptrace_report_syscall_exit include/linux/ptrace.h:489 [inline]
>>>  syscall_exit_work kernel/entry/common.c:249 [inline]
>>>  syscall_exit_to_user_mode_prepare+0xdb/0x230 kernel/entry/common.c:276
>>>  __syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
>>>  syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
>>>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>>>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>> RIP: 0033:0x7f0041a50b99
>>> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
>>> RSP: 002b:00007f0041a022f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
>>> RAX: 0000000000000200 RBX: 00007f0041ad8428 RCX: 00007f0041a50b99
>>> RDX: 0000000000000000 RSI: 00000000000045f5 RDI: 0000000000000003
>>> RBP: 00007f0041ad8420 R08: 0000000000000000 R09: 0000000000000004
>>> R10: 0000000000000009 R11: 0000000000000246 R12: 00007f0041aa6064
>>> R13: 0000000000000003 R14: 00007f0041a02400 R15: 0000000000022000
>>>  </TASK>
>>>
>>> Allocated by task 3861:
>>>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>>>  kasan_set_track mm/kasan/common.c:45 [inline]
>>>  set_alloc_info mm/kasan/common.c:436 [inline]
>>>  __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
>>>  kasan_slab_alloc include/linux/kasan.h:224 [inline]
>>>  slab_post_alloc_hook mm/slab.h:750 [inline]
>>>  slab_alloc_node mm/slub.c:3214 [inline]
>>>  slab_alloc mm/slub.c:3222 [inline]
>>>  __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
>>>  kmem_cache_alloc+0x204/0x3b0 mm/slub.c:3239
>>>  inet_bind2_bucket_create+0x37/0x360 net/ipv4/inet_hashtables.c:91
>>>  __inet_hash_connect+0xef5/0x1450 net/ipv4/inet_hashtables.c:951
>>>  dccp_v4_connect+0xc5c/0x16f0 net/dccp/ipv4.c:108
>>>  __inet_stream_connect+0x8cf/0xed0 net/ipv4/af_inet.c:660
>>>  inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:724
>>>  __sys_connect_file+0x14f/0x190 net/socket.c:1979
>>>  io_connect+0x15f/0x690 fs/io_uring.c:6724
>>>  io_issue_sqe+0x40c6/0xa9c0 fs/io_uring.c:8351
>>>  io_queue_sqe fs/io_uring.c:8706 [inline]
>>>  io_submit_sqe fs/io_uring.c:8968 [inline]
>>>  io_submit_sqes+0x16b0/0x8020 fs/io_uring.c:9079
>>>  __do_sys_io_uring_enter+0x117f/0x2360 fs/io_uring.c:12008
>>>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>>>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>>
>>> Freed by task 3861:
>>>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>>>  kasan_set_track+0x21/0x30 mm/kasan/common.c:45
>>>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
>>>  ____kasan_slab_free mm/kasan/common.c:366 [inline]
>>>  ____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
>>>  kasan_slab_free include/linux/kasan.h:200 [inline]
>>>  slab_free_hook mm/slub.c:1727 [inline]
>>>  slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
>>>  slab_free mm/slub.c:3507 [inline]
>>>  kmem_cache_free+0xdd/0x5a0 mm/slub.c:3524
>>>  inet_bind2_bucket_destroy net/ipv4/inet_hashtables.c:137 [inline]
>>>  inet_bind2_bucket_destroy net/ipv4/inet_hashtables.c:133 [inline]
>>>  __inet_put_port net/ipv4/inet_hashtables.c:174 [inline]
>>>  inet_put_port+0x4a0/0x6f0 net/ipv4/inet_hashtables.c:182
>>>  dccp_set_state+0x1be/0x3a0 net/dccp/proto.c:103
>>>  dccp_done+0x19/0x100 net/dccp/proto.c:138
>>>  dccp_rcv_state_process+0xc31/0x1820 net/dccp/input.c:662
>>>  dccp_v4_do_rcv+0xf9/0x1a0 net/dccp/ipv4.c:695
>>>  sk_backlog_rcv include/net/sock.h:1061 [inline]
>>>  __release_sock+0x134/0x3b0 net/core/sock.c:2849
>>>  release_sock+0x54/0x1b0 net/core/sock.c:3404
>>>  inet_stream_connect+0x76/0xa0 net/ipv4/af_inet.c:725
>>>  __sys_connect_file+0x14f/0x190 net/socket.c:1979
>>>  io_connect+0x15f/0x690 fs/io_uring.c:6724
>>>  io_issue_sqe+0x40c6/0xa9c0 fs/io_uring.c:8351
>>>  io_queue_sqe fs/io_uring.c:8706 [inline]
>>>  io_submit_sqe fs/io_uring.c:8968 [inline]
>>>  io_submit_sqes+0x16b0/0x8020 fs/io_uring.c:9079
>>>  __do_sys_io_uring_enter+0x117f/0x2360 fs/io_uring.c:12008
>>>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>>>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>>
>>> The buggy address belongs to the object at ffff888020cbc980
>>>  which belongs to the cache dccp_bind2_bucket of size 56
>>> The buggy address is located 0 bytes inside of
>>>  56-byte region [ffff888020cbc980, ffff888020cbc9b8)
>>>
>>> The buggy address belongs to the physical page:
>>> page:ffffea0000832f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x20cbc
>>> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
>>> raw: 00fff00000000200 0000000000000000 dead000000000122 ffff88802393ca00
>>> raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000
>>> page dumped because: kasan: bad access detected
>>> page_owner tracks the page as allocated
>>> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY), pid 3856, tgid 3855 (syz-executor537), ts 156131029362, free_ts 153495137859
>>>  prep_new_page mm/page_alloc.c:2456 [inline]
>>>  get_page_from_freelist+0x1290/0x3b70 mm/page_alloc.c:4198
>>>  __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5426
>>>  alloc_pages+0x1aa/0x310 mm/mempolicy.c:2272
>>>  alloc_slab_page mm/slub.c:1797 [inline]
>>>  allocate_slab+0x26c/0x3c0 mm/slub.c:1942
>>>  new_slab mm/slub.c:2002 [inline]
>>>  ___slab_alloc+0x985/0xd90 mm/slub.c:3002
>>>  __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3089
>>>  slab_alloc_node mm/slub.c:3180 [inline]
>>>  slab_alloc mm/slub.c:3222 [inline]
>>>  __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
>>>  kmem_cache_alloc+0x360/0x3b0 mm/slub.c:3239
>>>  inet_bind2_bucket_create+0x37/0x360 net/ipv4/inet_hashtables.c:91
>>>  __inet_hash_connect+0xef5/0x1450 net/ipv4/inet_hashtables.c:951
>>>  dccp_v4_connect+0xc5c/0x16f0 net/dccp/ipv4.c:108
>>>  __inet_stream_connect+0x8cf/0xed0 net/ipv4/af_inet.c:660
>>>  inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:724
>>>  __sys_connect_file+0x14f/0x190 net/socket.c:1979
>>>  io_connect+0x15f/0x690 fs/io_uring.c:6724
>>>  io_issue_sqe+0x40c6/0xa9c0 fs/io_uring.c:8351
>>>  io_queue_sqe fs/io_uring.c:8706 [inline]
>>>  io_submit_sqe fs/io_uring.c:8968 [inline]
>>>  io_submit_sqes+0x16b0/0x8020 fs/io_uring.c:9079
>>> page last free stack trace:
>>>  reset_page_owner include/linux/page_owner.h:24 [inline]
>>>  free_pages_prepare mm/page_alloc.c:1371 [inline]
>>>  free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1421
>>>  free_unref_page_prepare mm/page_alloc.c:3343 [inline]
>>>  free_unref_page+0x19/0x6a0 mm/page_alloc.c:3438
>>>  __unfreeze_partials+0x17c/0x1a0 mm/slub.c:2521
>>>  qlink_free mm/kasan/quarantine.c:168 [inline]
>>>  qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
>>>  kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:294
>>>  __kasan_slab_alloc+0xa2/0xc0 mm/kasan/common.c:446
>>>  kasan_slab_alloc include/linux/kasan.h:224 [inline]
>>>  slab_post_alloc_hook mm/slab.h:750 [inline]
>>>  slab_alloc_node mm/slub.c:3214 [inline]
>>>  kmem_cache_alloc_node+0x255/0x3f0 mm/slub.c:3264
>>>  __alloc_skb+0x215/0x340 net/core/skbuff.c:414
>>>  alloc_skb include/linux/skbuff.h:1426 [inline]
>>>  dccp_connect+0x204/0x720 net/dccp/output.c:560
>>>  dccp_v4_connect+0x1140/0x16f0 net/dccp/ipv4.c:128
>>>  __inet_stream_connect+0x8cf/0xed0 net/ipv4/af_inet.c:660
>>>  inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:724
>>>  __sys_connect_file+0x14f/0x190 net/socket.c:1979
>>>  io_connect+0x15f/0x690 fs/io_uring.c:6724
>>>  io_issue_sqe+0x40c6/0xa9c0 fs/io_uring.c:8351
>>>  io_queue_sqe fs/io_uring.c:8706 [inline]
>>>  io_submit_sqe fs/io_uring.c:8968 [inline]
>>>  io_submit_sqes+0x16b0/0x8020 fs/io_uring.c:9079
>>>
>>> Memory state around the buggy address:
>>>  ffff888020cbc880: fa fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>>>  ffff888020cbc900: fa fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>>> >ffff888020cbc980: fa fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>>>                    ^
>>>  ffff888020cbca00: fa fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>>>  ffff888020cbca80: fa fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
>>> ==================================================================
>>>
>> I will look into where inet_bind_bucket_create gets passed in a NULL
>> net and submit a follow-up.
>>
> I think this will be fixed when a separate lock is added for the bhash2 table.
> From the logs, it looks like there were two sockets on different port
> numbers that hashed to the same bhash2 hashbucket and were being
> accessed at the same time (eg one freeing the bind2 bucket from the
> cache, one iterating through the list of the hashbucket's bind2
> buckets and checking the bucket that was getting freed right as it was
> getting freed)

Agreed.

Currently it seems that indexes of bhash and bhash2 is not always 1:1 and
there can be a case that two sockets are hashed like:

  - (net, port_A) -> bhash[A]
  - (net, port_B) -> bhash[B]
  - (net, port_A, addr_A) -> bhash2[C]
  - (net, port_B, addr_B) -> bhash2[C]

Then lock_A and lock_B are held by different processes and the same bhash2
bucket is accessed concurrently.

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