octave, 75 bytes

Result

AC

Duration

1073ms

Code [DL]

m=scanf("%d%d");h=m(1);w=m(2);s=repmat('*',h,w);s(2:h-1,2:w-1)=' ';disp(s)

stdin

70
29

stdout

*****************************
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*****************************

stderr

octave: X11 DISPLAY environment variable not set
octave: disabling GUI features