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lzma: Make sure we don't dereference past array

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The two dimensional array p->posSlotEncoder[4][64] is being dereferenced
using the GetLenToPosState() macro which checks if len is less than 5,
and if so subtracts 2 from it. If len = 0, that is 0 - 2 = 4294967294.
Obviously we don't want to dereference that far out so we check if the
position found is greater or equal kNumLenToPosStates (4) and bail out.

N.B.: Upstream LZMA 18.05 and later has this function completely rewritten
without any history.

Fixes: CID 51526

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2020-07-09 03:05:23 +00:00 committed by Daniel Kiper
parent dc052e5ac7
commit 16c0dbf4bc
1 changed files with 8 additions and 2 deletions
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10
grub-core/lib/LzmaEnc.c
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@ -1877,13 +1877,19 @@ static SRes LzmaEnc_CodeOneBlock(CLzmaEnc *p, Bool useLimits, UInt32 maxPackSize
}
else
{
UInt32 posSlot;
UInt32 posSlot, lenToPosState;
RangeEnc_EncodeBit(&p->rc, &p->isRep[p->state], 0);
p->state = kMatchNextStates[p->state];
LenEnc_Encode2(&p->lenEnc, &p->rc, len - LZMA_MATCH_LEN_MIN, posState, !p->fastMode, p->ProbPrices);
pos -= LZMA_NUM_REPS;
GetPosSlot(pos, posSlot);
RcTree_Encode(&p->rc, p->posSlotEncoder[GetLenToPosState(len)], kNumPosSlotBits, posSlot);
lenToPosState = GetLenToPosState(len);
if (lenToPosState >= kNumLenToPosStates)
{
p->result = SZ_ERROR_DATA;
return CheckErrors(p);
}
RcTree_Encode(&p->rc, p->posSlotEncoder[lenToPosState], kNumPosSlotBits, posSlot);
if (posSlot >= kStartPosModelIndex)
{