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);
 

lib/decompress_unlzma.c

@@ -82,6 +82,11 @@ struct rc {
 #define RC_MODEL_TOTAL_BITS 11
 
 
+static int nofill(void *buffer, unsigned int len)
+{
+	return -1;
+}
+
 /* Called twice: once at startup and once in rc_normalize() */
 static void INIT rc_read(struct rc *rc)
 {
@@ -97,7 +102,10 @@ static inline void INIT rc_init(struct rc *rc,
 				       int (*fill)(void*, unsigned int),
 				       char *buffer, int buffer_size)
 {
+	if (fill)
 		rc->fill = fill;
+	else
+		rc->fill = nofill;
 	rc->buffer = (uint8_t *)buffer;
 	rc->buffer_size = buffer_size;
 	rc->buffer_end = rc->buffer + rc->buffer_size;