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x86/x86asm: fix panic on truncated VEX/EVEX prefix #25

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nsavoire wants to merge 1 commit into from
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x86/x86asm: fix panic on truncated VEX/EVEX prefix #25

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3 changes: 3 additions & 0 deletions x86/x86asm/avx.go
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,9 @@ func decodeAVX(src []byte, pos int, vex Prefix, vexIndex int, inst Inst, mode in

_ = evex_z // TODO: use zeroing mask if needed for output

if pos >= len(src) {
return inst, errors.New("truncated")
}
opbyte := src[pos]
pos++

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5 changes: 5 additions & 0 deletions x86/x86asm/decode_test.go
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Expand Up @@ -75,6 +75,11 @@ func TestDecodeDoesNotCrash(t *testing.T) {
[]byte{},
[]byte{0xc5},
[]byte{0xc4},
// Streams ending exactly at the end of a VEX or EVEX prefix,
// leaving no opcode byte.
[]byte{0xc5, 0xfc},
[]byte{0xc4, 0xe2, 0x7d},
[]byte{0x62, 0xf1, 0x7c, 0x48},
}
for _, test := range cases {
_, err := Decode([]byte(test), 64) // the only goal is that this line does not panic
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