CIFS: System crash with exception RIP smbCalcSize+0x9

Issue

• System crashed due to CIFS smb_hdr being null
• CIFS VFS: Unexpected lookup error -20

crash> bt
PID: 3175   TASK: ffff880239f06ab0  CPU: 1   COMMAND: "java"
 #0 [ffff880239f1ba20] machine_kexec at ffffffff8103fdbb
 #1 [ffff880239f1ba80] crash_kexec at ffffffff810d1f02
 #2 [ffff880239f1bb50] oops_end at ffffffff8154f060
 #3 [ffff880239f1bb80] no_context at ffffffff8105186b
 #4 [ffff880239f1bbd0] __bad_area_nosemaphore at ffffffff81051af5
 #5 [ffff880239f1bc20] bad_area at ffffffff81051c1e
 #6 [ffff880239f1bc50] __do_page_fault at ffffffff81052443
 #7 [ffff880239f1bd70] do_page_fault at ffffffff81550fee
 #8 [ffff880239f1bda0] page_fault at ffffffff8154e2e5
    [exception RIP: smbCalcSize+9]
    RIP: ffffffffa0540339  RSP: ffff880239f1be58  RFLAGS: 00010202
    RAX: 0000000000000004  RBX: ffff880237c5c980  RCX: 0000000000000002
    RDX: 0000000000000000  RSI: ffff880239f1bf38  RDI: 0000000000000000
    RBP: ffff880239f1be58   R8: 00007f1058044170   R9: ffff880235976800
    R10: 0000000000000008  R11: 0000000000000246  R12: ffff88023591f180
    R13: 0000000000000000  R14: ffff88023591f220  R15: 0000000000000002
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
 #9 [ffff880239f1be60] cifs_readdir at ffffffffa054792f [cifs]
#10 [ffff880239f1bee0] vfs_readdir at ffffffff811b0b50
#11 [ffff880239f1bf30] sys_getdents at ffffffff811b0cd9
#12 [ffff880239f1bf80] system_call_fastpath at ffffffff8100b0d2
    RIP: 00000033a52a9035  RSP: 00007f1050873628  RFLAGS: 00010202
    RAX: 000000000000004e  RBX: ffffffff8100b0d2  RCX: 0000000000000002
    RDX: 0000000000008000  RSI: 00007f1058044170  RDI: 000000000000003e
    RBP: 00007f105804c180   R8: 00007f1058044170   R9: 0000000000000008
    R10: 0000000000000008  R11: 0000000000000246  R12: 0000000000000002
    R13: ffffffffffffffa8  R14: 00007f1050873710  R15: 00007f1058044140
    ORIG_RAX: 000000000000004e  CS: 0033  SS: 002b