linux-kernel - [patch] decompress_bunzip2: off by one in get_next

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Message-ID: <20141022081615.GD31384@mwanda>
Date:	Wed, 22 Oct 2014 11:16:15 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Alain Knaff <alain@...ff.lu>
Cc:	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: [patch] decompress_bunzip2: off by one in get_next_block()

"origPtr" is used as an offset into the bd->dbuf[] array.  That array
is allocated in start_bunzip() and has "bd->dbufSize" number of elements
so the test here should be >= instead of >.

Later we check "origPtr" again before using it as an offset so I don't
know if this bug can be triggered in real life.

Fixes: bc22c17e12c1 ('bzip2/lzma: library support for gzip, bzip2 and lzma decompression')
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/lib/decompress_bunzip2.c b/lib/decompress_bunzip2.c
index 8290e0b..6dd0335 100644
--- a/lib/decompress_bunzip2.c
+++ b/lib/decompress_bunzip2.c
@@ -184,7 +184,7 @@ static int INIT get_next_block(struct bunzip_data *bd)
 	if (get_bits(bd, 1))
 		return RETVAL_OBSOLETE_INPUT;
 	origPtr = get_bits(bd, 24);
-	if (origPtr > dbufSize)
+	if (origPtr >= dbufSize)
 		return RETVAL_DATA_ERROR;
 	/* mapping table: if some byte values are never used (encoding things
 	   like ascii text), the compression code removes the gaps to have fewer
--
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