Message-ID: <CACT4Y+b+DFpa34E3UWzSYn6qy-BMmxN80ikdmU_xMe9x9JF2+Q@mail.gmail.com>
Date:   Wed, 13 Jun 2018 09:51:44 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+4c20b3866171ce8441d2@...kaller.appspotmail.com>,
        Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:     David Miller <davem@...emloft.net>,
        LKML <linux-kernel@...r.kernel.org>, linux-rdma@...r.kernel.org,
        netdev <netdev@...r.kernel.org>, rds-devel@....oracle.com,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in rds_cong_queue_updates

On Wed, Jun 13, 2018 at 4:51 AM, syzbot
<syzbot+4c20b3866171ce8441d2@...kaller.appspotmail.com> wrote:
> syzbot has found a reproducer for the following crash on:

Woohoo! Please take a look, this is a top crasher.

> HEAD commit:    f0dc7f9c6dd9 Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1461f03f800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=fa9c20c48788d1c1
> dashboard link: https://syzkaller.appspot.com/bug?extid=4c20b3866171ce8441d2
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=16cbfeaf800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=165227f7800000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+4c20b3866171ce8441d2@...kaller.appspotmail.com
>
> IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
> 8021q: adding VLAN 0 to HW filter on device team0
> IPVS: ftp: loaded support on port[0] = 21
> IPVS: ftp: loaded support on port[0] = 21
> ==================================================================
> BUG: KASAN: use-after-free in atomic_read
> include/asm-generic/atomic-instrumented.h:21 [inline]
> BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:42
> [inline]
> BUG: KASAN: use-after-free in check_net include/net/net_namespace.h:236
> [inline]
> BUG: KASAN: use-after-free in rds_destroy_pending net/rds/rds.h:897 [inline]
> BUG: KASAN: use-after-free in rds_cong_queue_updates+0x255/0x590
> net/rds/cong.c:226
> Read of size 4 at addr ffff8801ab180044 by task syz-executor199/4800
>
> CPU: 1 PID: 4800 Comm: syz-executor199 Not tainted 4.17.0+ #84
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  check_memory_region_inline mm/kasan/kasan.c:260 [inline]
>  check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
>  kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
>  atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
>  refcount_read include/linux/refcount.h:42 [inline]
>  check_net include/net/net_namespace.h:236 [inline]
>  rds_destroy_pending net/rds/rds.h:897 [inline]
>  rds_cong_queue_updates+0x255/0x590 net/rds/cong.c:226
>  rds_recv_rcvbuf_delta.part.3+0x211/0x350 net/rds/recv.c:126
>  rds_recv_rcvbuf_delta net/rds/recv.c:735 [inline]
>  rds_clear_recv_queue+0x2f0/0x4c0 net/rds/recv.c:735
>  rds_release+0x15c/0x550 net/rds/af_rds.c:72
>  __sock_release+0xd7/0x260 net/socket.c:603
>  sock_close+0x19/0x20 net/socket.c:1186
>  __fput+0x353/0x890 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x1e4/0x290 kernel/task_work.c:113
>  exit_task_work include/linux/task_work.h:22 [inline]
>  do_exit+0x1aee/0x2730 kernel/exit.c:865
>  do_group_exit+0x16f/0x430 kernel/exit.c:968
>  get_signal+0x886/0x1960 kernel/signal.c:2468
>  do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
>  exit_to_usermode_loop+0x2cf/0x360 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:293
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x44f439
> Code: e8 ac be 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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
> 0f 83 5b ff fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fc65567dcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 00000000006edadc RCX: 000000000044f439
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006edadc
> RBP: 00000000006edad8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fff3df31b1f R14: 00007fc65567e9c0 R15: 0000000000000061
>
> Allocated by task 4800:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
>  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
>  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
>  kmem_cache_zalloc include/linux/slab.h:696 [inline]
>  net_alloc net/core/net_namespace.c:383 [inline]
>  copy_net_ns+0x159/0x4c0 net/core/net_namespace.c:423
>  create_new_namespaces+0x69d/0x8f0 kernel/nsproxy.c:107
>  unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:206
>  ksys_unshare+0x708/0xf90 kernel/fork.c:2411
>  __do_sys_unshare kernel/fork.c:2479 [inline]
>  __se_sys_unshare kernel/fork.c:2477 [inline]
>  __x64_sys_unshare+0x31/0x40 kernel/fork.c:2477
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 746:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>  __cache_free mm/slab.c:3498 [inline]
>  kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
>  net_free net/core/net_namespace.c:399 [inline]
>  net_drop_ns.part.14+0x11a/0x130 net/core/net_namespace.c:406
>  net_drop_ns net/core/net_namespace.c:405 [inline]
>  cleanup_net+0x6a1/0xb20 net/core/net_namespace.c:541
>  process_one_work+0xc64/0x1b70 kernel/workqueue.c:2153
>  worker_thread+0x181/0x13a0 kernel/workqueue.c:2296
>  kthread+0x345/0x410 kernel/kthread.c:240
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
>
> The buggy address belongs to the object at ffff8801ab180040
>  which belongs to the cache net_namespace(17:syz0) of size 8896
> The buggy address is located 4 bytes inside of
>  8896-byte region [ffff8801ab180040, ffff8801ab182300)
> The buggy address belongs to the page:
> page:ffffea0006ac6000 count:1 mapcount:0 mapping:ffff8801aeaa0080 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
> raw: 02fffc0000008100 ffff8801d3827048 ffff8801d3827048 ffff8801aeaa0080
> raw: 0000000000000000 ffff8801ab180040 0000000100000001 ffff8801ab7cae40
> page dumped because: kasan: bad access detected
> page->mem_cgroup:ffff8801ab7cae40
>
> Memory state around the buggy address:
>  ffff8801ab17ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff8801ab17ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                                            ^
>  ffff8801ab180080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801ab180100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
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