lzma/gzip: fix potential oops when input data is truncated

If the lzma/gzip decompressors are called with insufficient input data
(len > 0 & fill = NULL), they will attempt to call the fill function to
obtain more data, leading to a kernel oops.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/decompress_inflate.c

@@ -27,6 +27,11 @@
 
 #define GZIP_IOBUF_SIZE (16*1024)
 
+static int nofill(void *buffer, unsigned int len)
+{
+	return -1;
+}
+
 /* Included from initramfs et al code */
 STATIC int INIT gunzip(unsigned char *buf, int len,
 		       int(*fill)(void*, unsigned int),
@@ -76,6 +81,9 @@ STATIC int INIT gunzip(unsigned char *buf, int len,
 		goto gunzip_nomem4;
 	}
 
+	if (!fill)
+		fill = nofill;
+
 	if (len == 0)
 		len = fill(zbuf, GZIP_IOBUF_SIZE);