panic handing cifs reconnect in cifs_send_recv or smb2_reconnect or mutex_unlock due to a use after free of struct cifs_ses

Issue

• kernel crashed with one of the following logs:
• crash log 1

[3391089.999306] general protection fault: 0000 [#1] SMP 
[3391090.008015] Workqueue: cifsiod smb2_reconnect_server [cifs]
[3391090.010236] RIP: 0010:[<ffffffffc07c5599>]  [<ffffffffc07c5599>] cifs_send_recv+0x2b9/0x3d0 [cifs]

• crash log 2

[87704.045236] CPU: 38 PID: 84826 Comm: kworker/38:3 Kdump: loaded Tainted: P           OEL ------------   3.10.0-957.5.1.el7.x86_64 #1
[87704.045237] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 06/07/2018
[87704.045250] Workqueue: cifsiod smb2_reconnect_server [cifs]
[87704.045252] task: ffff8f9356e691a0 ti: ffff8f992d688000 task.ti: ffff8f992d688000
[87704.045254] RIP: 0010:[<ffffffffc1b4ac88>]  [<ffffffffc1b4ac88>] smb2_reconnect+0x58/0x440 [cifs]

• crash log 3

[ 1979.225457] CIFS VFS: Send error in SessSetup = -11 
[ 1979.230363] BUG: unable to handle kernel NULL pointer dereference at 0000000000000040 
[ 1979.323028] CPU: 2 PID: 20198 Comm: kworker/2:0 Kdump: loaded Tainted: G           OE  ------------   3.10.0-957.27.4.el7.x86_64 #1 
[ 1979.334840] Hardware name: IBM IBM System x -[7944Q05]-/90Y4784, BIOS -[D6E150CUS-1.11]- 02/08/2011 
[ 1979.343915] Workqueue: cifsiod smb2_reconnect_server [cifs] 
[ 1979.349509] task: ffff90bf7c80c100 ti: ffff90c05de3c000 task.ti: ffff90c05de3c000 
[ 1979.356988] RIP: 0010:[<ffffffffabd68136>]  [<ffffffffabd68136>] mutex_unlock+0x6/0x20 

• crash log 4

[306077.305516] CIFS VFS: Free previous auth_key.response = ffff9270dc7eea00
[311947.893637] CIFS VFS: ioctl error in smb2_get_dfs_refer rc=-5
[312003.006874] CIFS VFS: ioctl error in smb2_get_dfs_refer rc=-5
[312075.420999] BUG: unable to handle kernel NULL pointer dereference at           (null)
[312075.422137] IP: [<ffffffff8db96919>] __list_del_entry+0x29/0xd0
[312075.423169] PGD 8000000278b68067 PUD 1445d3067 PMD 12330c067 PTE 0
[312075.424180] Oops: 0000 [#1] SMP 
[312075.430209] CPU: 1 PID: 18436 Comm: kworker/1:4 Kdump: loaded Not tainted 3.10.0-957.27.2.el7.x86_64 #1
[312075.431187] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/05/2016
[312075.432178] Workqueue: cifsiod smb2_reconnect_server [cifs]
[312075.433139] task: ffff926dc6545140 ti: ffff926ce1168000 task.ti: ffff926ce1168000
[312075.434068] RIP: 0010:[<ffffffff8db96919>]  [<ffffffff8db96919>] __list_del_entry+0x29/0xd0