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grub2/SOURCES/0290-lzma-Make-sure-we-don-...

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Thu, 9 Jul 2020 03:05:23 +0000
Subject: [PATCH] lzma: Make sure we don't dereference past array
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>
Upstream-commit-id: f91e043bda4
---
grub-core/lib/LzmaEnc.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/grub-core/lib/LzmaEnc.c b/grub-core/lib/LzmaEnc.c
index f2ec04a8c..753e56a95 100644
--- a/grub-core/lib/LzmaEnc.c
+++ b/grub-core/lib/LzmaEnc.c
@@ -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)
{