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Fix crashes in ConvertToVectorRep and CopyToVectorRep #5126

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merged 1 commit into from
Oct 19, 2022
Merged

Fix crashes in ConvertToVectorRep and CopyToVectorRep #5126

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26 changes: 17 additions & 9 deletions src/vec8bit.c
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Original file line number Diff line number Diff line change
Expand Up @@ -528,10 +528,17 @@ static void RewriteVec8Bit(Obj vec, UInt q)

if (q1 == q)
return;
assert(q > q1);

if (q < q1) {
ErrorMayQuit("Cannot convert a vector compressed over GF(%i) to small field GF(%i)", q1, q);
}

if (((q - 1) % (q1 - 1)) != 0) {
ErrorMayQuit("Cannot convert a vector compressed over GF(%i) to GF(%i)", q1, q);
}

if (DoFilter(IsLockedRepresentationVector, vec) == True) {
ErrorMayQuit("You cannot convert a locked vector compressed over "
ErrorMayQuit("Cannot convert a locked vector compressed over "
"GF(%i) to GF(%i)",
q1, q);
}
Expand Down Expand Up @@ -563,7 +570,6 @@ static void RewriteVec8Bit(Obj vec, UInt q)
byte = 0;
i = len - 1;

assert(((q - 1) % (q1 - 1)) == 0);
mult = (q - 1) / (q1 - 1);
while (i >= 0) {
val = VAL_FFE(convtab1[gettab1[byte1 + 256 * (i % els1)]]);
Expand Down Expand Up @@ -609,7 +615,7 @@ void RewriteGF2Vec(Obj vec, UInt q)
assert(q % 2 == 0);

if (DoFilter(IsLockedRepresentationVector, vec) == True) {
ErrorMayQuit("You cannot convert a locked vector compressed over "
ErrorMayQuit("Cannot convert a locked vector compressed over "
"GF(2) to GF(%i)",
q, 0);
}
Expand Down Expand Up @@ -685,9 +691,10 @@ static void ConvVec8Bit(Obj list, UInt q)

// already in the correct representation
if (IS_VEC8BIT_REP(list)) {
if (FIELD_VEC8BIT(list) == q)
UInt q1 = FIELD_VEC8BIT(list);
if (q1 == q)
return;
else if (FIELD_VEC8BIT(list) < q) {
else if (q1 < q && ((q - 1) % (q1 - 1)) == 0) {
RewriteVec8Bit(list, q);
return;
}
Expand Down Expand Up @@ -836,14 +843,15 @@ static Obj NewVec8Bit(Obj list, UInt q)

// already in the correct representation
if (IS_VEC8BIT_REP(list)) {
if (FIELD_VEC8BIT(list) == q) {
UInt q1 = FIELD_VEC8BIT(list);
if (q1 == q) {
res = CopyVec8Bit(list, 1);
if (!IS_MUTABLE_OBJ(list))
// index 0 is for immutable vectors
SetTypeDatObj(res, TypeVec8Bit(q, 0));
return res;
}
else if (FIELD_VEC8BIT(list) < q) {
else if (q1 < q && ((q - 1) % (q1 - 1)) == 0) {
// rewriting to a larger field
res = CopyVec8Bit(list, 1);
RewriteVec8Bit(res, q);
Expand Down Expand Up @@ -1003,7 +1011,7 @@ static Obj FuncPLAIN_VEC8BIT(Obj self, Obj list)
RequireArgument(SELF_NAME, list, "must be an 8bit vector");
}
if (DoFilter(IsLockedRepresentationVector, list) == True) {
ErrorMayQuit("You cannot convert a locked vector compressed over "
ErrorMayQuit("Cannot convert a locked vector compressed over "
"GF(%i) to a plain list",
FIELD_VEC8BIT(list), 0);
}
Expand Down
16 changes: 16 additions & 0 deletions tst/testbugfix/2022-10-18-RewriteVec8Bit.tst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
# avoid crashes when converting certain compressed vectors
# see <https://github.com/gap-system/gap/issues/5123>

#
gap> v:= [ 0 * Z(2) ];;
gap> ConvertToVectorRep( v, 4 );
4
gap> ConvertToVectorRep( v, 8 );
8

#
gap> v:= [ 0 * Z(2) ];;
gap> ConvertToVectorRep( v, 4 );
4
gap> CopyToVectorRep( v, 8 );
[ 0*Z(2) ]