netdev - Crash due to destroying TCP request sockets using SOCK

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Date:   Thu, 05 Jul 2018 20:37:03 -0600
From:   Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
To:     netdev@...r.kernel.org, eric.dumazet@...il.com, lorenzo@...gle.com
Subject: Crash due to destroying TCP request sockets using SOCK_DESTROY

We are seeing a crash on an ARM64 device with Android 4.14 based kernel.

 From the call stack, a TCP socket is being destroyed using netlink_diag.
The memory dump showed that the socket was an inet request socket (in
state TCP_NEW_SYN_RECV) with refcount of 0.

The crash seems to have happened during a regression test where wifi
was toggled with some browser activity but it is not very easily
reproducible. I believe netd on Android tries to destroy all sockets in
a system on change of network.

  13232.479820:   <2> refcount_t: underflow; use-after-free.
  13232.479838:   <6> ------------[ cut here ]------------
  13232.479843:   <6> kernel BUG at kernel/msm-4.14/lib/refcount.c:204!
  13232.479849:   <6> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
  13232.479895:   <6> CPU: 4 PID: 648 Comm: netd Tainted: G S      W  O   
  4.14.49+ #1
  13232.479897:   <6> task: fffffff5d6e28080 task.stack: ffffff801cf98000
  13232.479908:   <2> pc : refcount_sub_and_test+0x64/0x78
  13232.479910:   <2> lr : refcount_sub_and_test+0x64/0x78
  13232.479911:   <2> sp : ffffff801cf9ba40 pstate : 20400145
  13232.479911:   <2> x29: ffffff801cf9ba40 x28: fffffff5d6e28080
  13232.479914:   <2> x27: ffffff801cf9bd10 x26: fffffff4a1428f40
  13232.479915:   <2> x25: 0000000000000000 x24: ffffffffffffff91
  13232.479917:   <2> x23: 0000000000000015 x22: fffffff5b837c880
  13232.479919:   <2> x21: fffffff4a1428f40 x20: 0000000000000000
  13232.479920:   <2> x19: fffffff4c47c6088 x18: e7b13cd1ecbfea00
  13232.479922:   <2> x17: 00000008ec3bb553 x16: 011d8776aa792786
  13232.479924:   <2> x15: e7b13cd1ecbfea00 x14: 000000002bdb7692
  13232.479925:   <2> x13: 0000000000000000 x12: e7b13cd1ecbfea00
  13232.479927:   <2> x11: e7b13cd1ecbfea00 x10: 0000000000000000
  13232.479928:   <2> x9 : e7b13cd1ecbfea00 x8 : 0000000000000000
  13232.479929:   <2> x7 : 0000000000000001 x6 : 0000000000000001
  13232.479931:   <2> x5 : 0000000000000000 x4 : 00000c08ed425d69
  13232.479932:   <2> x3 : 00000066effb6000 x2 : ffffff8f09dc5000
  13232.479934:   <2> x1 : 0000000000000000 x0 : 0000000000000026
  13232.479996:   <6> Process netd (pid: 648, stack limit = 
0xffffff801cf98000)
  13232.479998:   <2> Call trace:
  13232.480000:   <2>  refcount_sub_and_test+0x64/0x78
  13232.480002:   <2>  refcount_dec_and_test+0x18/0x24
  13232.480005:   <2>  sock_gen_put+0x1c/0xb0
  13232.480009:   <2>  tcp_diag_destroy+0x54/0x68
  13232.480010:   <2>  inet_diag_cmd_exact+0x78/0xa0
  13232.480012:   <2>  inet_diag_handler_cmd+0xcc/0xf8
  13232.480018:   <2>  sock_diag_rcv_msg+0x130/0x158
  13232.480021:   <2>  netlink_rcv_skb+0xa4/0x11c
  13232.480023:   <2>  sock_diag_rcv+0x34/0x48
  13232.480025:   <2>  netlink_unicast+0x158/0x1f0
  13232.480026:   <2>  netlink_sendmsg+0x334/0x340
  13232.480028:   <2>  sock_sendmsg+0x44/0x60
  13232.480031:   <2>  sock_write_iter+0xac/0xf4
  13232.480034:   <2>  __vfs_write+0x124/0x154
  13232.480036:   <2>  vfs_write+0xcc/0x188
  13232.480038:   <2>  SyS_write+0x60/0xc0
  13232.480040:   <2>  el0_svc_naked+0x34/0x38
  13232.480042:   <6> Code: 910003fd f0008200 910fd000 97f4158c 
(d4210000)
  13232.480045:   <6> ---[ end trace 994bad5b8077e394 ]---
  13232.480061:   <6> Kernel panic - not syncing: Fatal exception

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