linux-kernel - [PATCH 4/4] Decompressors: Validate match distance in decompress

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Message-Id: <201011231225.42440.lasse.collin@tukaani.org>
Date:	Tue, 23 Nov 2010 12:25:42 +0200
From:	Lasse Collin <lasse.collin@...aani.org>
To:	linux-kernel@...r.kernel.org
Cc:	"H. Peter Anvin" <hpa@...or.com>, Alain Knaff <alain@...ff.lu>,
	Albin Tonnerre <albin.tonnerre@...e-electrons.com>,
	Phillip Lougher <phillip@...gher.demon.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 4/4] Decompressors: Validate match distance in decompress_unlzma.c

From: Lasse Collin <lasse.collin@...aani.org>

Validate the newly decoded distance (rep0) in process_bit1().
This is to detect corrupt LZMA data quickly. The old code can
run for long time producing garbage until it hits the end of
the input.

Signed-off-by: Lasse Collin <lasse.collin@...aani.org>
---

--- linux-2.6.37-rc3/lib/decompress_unlzma.c.orig	2010-11-23 11:11:58.000000000 +0200
+++ linux-2.6.37-rc3/lib/decompress_unlzma.c	2010-11-23 11:13:30.000000000 +0200
@@ -528,6 +528,9 @@ static inline int INIT process_bit1(stru
 			cst->rep0 = pos_slot;
 		if (++(cst->rep0) == 0)
 			return 0;
+		if (cst->rep0 > wr->header->dict_size
+				|| cst->rep0 > get_pos(wr))
+			return -1;
 	}
 
 	len += LZMA_MATCH_MIN_LEN;
--
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