bunzip2: fix rare decompression failure

The decompression code parses a huffman tree and counts the number of
symbols for a given bit length.  In rare cases, there may be >= 256
symbols with a given bit length, causing the unsigned char to overflow.
This causes a decompression failure later when the code tries and fails to
find the bit length for a given symbol.

Since the maximum number of symbols is 258, use unsigned short instead.

Fixes: ab77e81f65 ("x86/dom0: support bzip2 and lzma compressed bzImage payloads")
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
master commit: 303d3ff85c
master date: 2024-07-30 11:55:56 +0200

xen/common/bunzip2.c

@@ -221,7 +221,8 @@ static int __init get_next_block(struct bunzip_data *bd)
 	   RUNB) */
 	symCount = symTotal+2;
 	for (j = 0; j < groupCount; j++) {
-		unsigned char length[MAX_SYMBOLS], temp[MAX_HUFCODE_BITS+1];
+		unsigned char length[MAX_SYMBOLS];
+		unsigned short temp[MAX_HUFCODE_BITS+1];
 		int	minLen,	maxLen, pp;
 		/* Read Huffman code lengths for each symbol.  They're
 		   stored in a way similar to mtf; record a starting