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Avoid integer overflow in bios_disk

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Coverity warns about potential integer overflow on 32-bit value before
widening the calculation result to 64-bit.
This commit is contained in:
Patryk Obara 2020-03-01 04:05:59 +01:00 • committed by Patryk Obara
parent 19d1caa483
commit 2bbe181ccb
1 changed files with 12 additions and 5 deletions
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17
src/ints/bios_disk.cpp
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@ -519,11 +519,18 @@ static Bitu INT13_DiskHandler(void) {
CALLBACK_SCF(true);
return CBRET_NONE;
}
Bit32u tmpheads, tmpcyl, tmpsect, tmpsize;
imageDiskList[drivenum]->Get_Geometry(&tmpheads, &tmpcyl, &tmpsect, &tmpsize);
Bit64u largesize = tmpheads*tmpcyl*tmpsect*tmpsize;
largesize/=512;
Bit32u ts = static_cast<Bit32u>(largesize);
uint32_t tmpheads, tmpcyl, tmpsect, tmpsize;
imageDiskList[drivenum]->Get_Geometry(&tmpheads, &tmpcyl,
&tmpsect, &tmpsize);
// Store intermediate calculations in 64-bit to avoid
// accidental integer overflow on temporary value:
uint64_t largesize = tmpheads;
largesize *= tmpcyl;
largesize *= tmpsect;
largesize *= tmpsize;
const uint32_t ts = static_cast<uint32_t>(largesize / 512);
reg_ah = (drivenum <2)?1:3; //With 2 for floppy MSDOS starts calling int 13 ah 16
if(reg_ah == 3) {
reg_cx = static_cast<Bit16u>(ts >>16);