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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Date: Thu, 9 Jul 2020 03:05:23 +0000
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Subject: [PATCH] lzma: Make sure we don't dereference past array
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The two dimensional array p->posSlotEncoder[4][64] is being dereferenced
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using the GetLenToPosState() macro which checks if len is less than 5,
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and if so subtracts 2 from it. If len = 0, that is 0 - 2 = 4294967294.
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Obviously we don't want to dereference that far out so we check if the
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position found is greater or equal kNumLenToPosStates (4) and bail out.
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N.B.: Upstream LZMA 18.05 and later has this function completely rewritten
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without any history.
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Fixes: CID 51526
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Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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Upstream-commit-id: f91e043bda4
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---
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grub-core/lib/LzmaEnc.c | 10 ++++++++--
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1 file changed, 8 insertions(+), 2 deletions(-)
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diff --git a/grub-core/lib/LzmaEnc.c b/grub-core/lib/LzmaEnc.c
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index f2ec04a8c28..753e56a95e3 100644
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--- a/grub-core/lib/LzmaEnc.c
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+++ b/grub-core/lib/LzmaEnc.c
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@@ -1877,13 +1877,19 @@ static SRes LzmaEnc_CodeOneBlock(CLzmaEnc *p, Bool useLimits, UInt32 maxPackSize
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}
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else
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{
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- UInt32 posSlot;
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+ UInt32 posSlot, lenToPosState;
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RangeEnc_EncodeBit(&p->rc, &p->isRep[p->state], 0);
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p->state = kMatchNextStates[p->state];
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LenEnc_Encode2(&p->lenEnc, &p->rc, len - LZMA_MATCH_LEN_MIN, posState, !p->fastMode, p->ProbPrices);
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pos -= LZMA_NUM_REPS;
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GetPosSlot(pos, posSlot);
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- RcTree_Encode(&p->rc, p->posSlotEncoder[GetLenToPosState(len)], kNumPosSlotBits, posSlot);
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+ lenToPosState = GetLenToPosState(len);
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+ if (lenToPosState >= kNumLenToPosStates)
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+ {
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+ p->result = SZ_ERROR_DATA;
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+ return CheckErrors(p);
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+ }
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+ RcTree_Encode(&p->rc, p->posSlotEncoder[lenToPosState], kNumPosSlotBits, posSlot);
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if (posSlot >= kStartPosModelIndex)
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{
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