syzbot

panic: mutex 0xffffWAfRd8N0I7NeG:b7 8S8PL1 8 noNtO T heLOlWd EiREnD m tOxN SY_SlCeaALL v7e5 5
36S8t7a09r1t2i ngE XIsTta c0k  at
racStopped at      savectx+0xae:   movl    $0,%gs:0x680
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*500123  27258      0           0  0x4000000    1  syz-executor
savectx() at savectx+0xae
end of kernel
end trace frame: 0x4913e54270, count: 14
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