[build] Round up SUBx deltas

The zbin compressor fixup utility rounds down file sizes before calculating their difference. This produces incorrect values and may cause truncated gPXE images to be loaded at boot. The following example explains the problem: ilen = 48 bytes (uncompressed input file) olen = 17 bytes (compressed output file) divisor = 16 bytes (paragraph granularity) fixmeup = 3 paragraphs (value to fix up) olen / divisor - ilen / divisor = 1 - 3 = -2 paragraphs (old delta calculation) ( align ( olen, divisor ) - align ( ilen, divisor ) ) / divisor = 2 - 3 = -1 paragraphs (new delta calculation) If we perform the SUBx operation with old delta: fixmeup + -2 = 1 paragraph gets loaded by the prefix With the new delta: fixmeup + -1 = 2 paragraphs get loaded by the prefix The old delta calculation removes the last paragraph; the prefix will load a truncated copy of gPXE into memory. We need to load 2 paragraphs since olen is 17 bytes. Loading only 1 paragraph (16 bytes) would truncate the last byte. Signed-off-by: Michael Brown <mcb30@etherboot.org>
ipxe · Apr 15, 2009 · b149a99 · b149a99
1 parent f44205b
commit b149a99
Showing 1 changed file with 10 additions and 7 deletions.
diff --git a/src/util/zbin.c b/src/util/zbin.c
@@ -57,6 +57,10 @@ struct zinfo_file {
 	unsigned int num_entries;
 };
 
+static unsigned long align ( unsigned long value, unsigned long align ) {
+	return ( ( value + align - 1 ) & ~( align - 1 ) );
+}
+
 static int read_file ( const char *filename, void **buf, size_t *len ) {
 	FILE *file;
 	struct stat stat;
@@ -140,14 +144,13 @@ static int process_zinfo_copy ( struct input_file *input,
 	struct zinfo_copy *copy = &zinfo->copy;
 	size_t offset = copy->offset;
 	size_t len = copy->len;
-	unsigned int align = copy->align;
 
 	if ( ( offset + len ) > input->len ) {
 		fprintf ( stderr, "Input buffer overrun on copy\n" );
 		return -1;
 	}
 
-	output->len = ( ( output->len + align - 1 ) & ~( align - 1 ) );
+	output->len = align ( output->len, copy->align );
 	if ( ( output->len + len ) > output->max_len ) {
 		fprintf ( stderr, "Output buffer overrun on copy\n" );
 		return -1;
@@ -170,15 +173,14 @@ static int process_zinfo_pack ( struct input_file *input,
 	struct zinfo_pack *pack = &zinfo->pack;
 	size_t offset = pack->offset;
 	size_t len = pack->len;
-	unsigned int align = pack->align;
 	unsigned long packed_len;
 
 	if ( ( offset + len ) > input->len ) {
 		fprintf ( stderr, "Input buffer overrun on pack\n" );
 		return -1;
 	}
 
-	output->len = ( ( output->len + align - 1 ) & ~( align - 1 ) );
+	output->len = align ( output->len, pack->align );
 	if ( output->len > output->max_len ) {
 		fprintf ( stderr, "Output buffer overrun on pack\n" );
 		return -1;
@@ -222,8 +224,9 @@ static int process_zinfo_subtract ( struct input_file *input,
 	}
 
 	target = ( output->buf + offset );
-	delta = ( ( output->len / subtract->divisor ) -
-		  ( input->len / subtract->divisor ) );
+	delta = ( ( align ( output->len, subtract->divisor ) -
+		    align ( input->len, subtract->divisor ) )
+		  / subtract->divisor );
 
 	switch ( datasize ) {
 	case 1: {
@@ -251,7 +254,7 @@ static int process_zinfo_subtract ( struct input_file *input,
 	}
 
 	if ( DEBUG ) {
-		fprintf ( stderr, "SUBx [%#zx,%#zx) (%#lx+(%#lx/%#lx)-(%#lx/%#lx)) = %#lx\n",
+		fprintf ( stderr, "SUBx [%#zx,%#zx) (%#lx+(%#lx/%#x)-(%#lx/%#x)) = %#lx\n",
 			  offset, ( offset + datasize ), old, output->len, subtract->divisor,
 			  input->len, subtract->divisor, new );
 	}