linux-kernel - [PATCH] Decompressors: Check input size in decompress

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Date:	Fri, 26 Nov 2010 20:23:43 +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] Decompressors: Check input size in decompress_inflate.c

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

Check for end of the input buffer when skipping over
the filename field in the .gz file header.

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

diff -uprN linux-2.6.37-rc3.orig/lib/decompress_inflate.c linux-2.6.37-rc3/lib/decompress_inflate.c
--- linux-2.6.37-rc3.orig/lib/decompress_inflate.c	2010-10-20 23:30:22.000000000 +0300
+++ linux-2.6.37-rc3/lib/decompress_inflate.c	2010-11-26 19:42:15.000000000 +0200
@@ -100,13 +100,22 @@ STATIC int INIT gunzip(unsigned char *bu
 	 * possible asciz filename)
 	 */
 	strm->next_in = zbuf + 10;
+	strm->avail_in = len - 10;
 	/* skip over asciz filename */
 	if (zbuf[3] & 0x8) {
-		while (strm->next_in[0])
-			strm->next_in++;
-		strm->next_in++;
+		do {
+			/*
+			 * If the filename doesn't fit into the buffer,
+			 * the file is very probably corrupt. Don't try
+			 * to read more data.
+			 */
+			if (strm->avail_in == 0) {
+				error("header error");
+				goto gunzip_5;
+			}
+			--strm->avail_in;
+		} while (*strm->next_in++);
 	}
-	strm->avail_in = len - (strm->next_in - zbuf);
 
 	strm->next_out = out_buf;
 	strm->avail_out = out_len;
--
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