[slam] Avoid potential division by zero

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/net/udp/slam.c b/src/net/udp/slam.c
index 8b26bfb3cc141ff962c4fb3d5397e679bf1bb3aa..8fcc97632b050c7e3f561956e431a6c68fa0c1eb 100644 (file)
--- a/src/net/udp/slam.c
+++ b/src/net/udp/slam.c
@@ -415,6 +415,8 @@ static int slam_pull_value ( struct slam_request *slam,
 static int slam_pull_header ( struct slam_request *slam,
                              struct io_buffer *iobuf ) {
        void *header = iobuf->data;
+       unsigned long total_bytes;
+       unsigned long block_size;
        int rc;
 
        /* If header matches cached header, just pull it and return */
@@ -431,22 +433,26 @@ static int slam_pull_header ( struct slam_request *slam,
         */
        if ( ( rc = slam_pull_value ( slam, iobuf, NULL ) ) != 0 )
                return rc;
-       if ( ( rc = slam_pull_value ( slam, iobuf,
-                                     &slam->total_bytes ) ) != 0 )
+       if ( ( rc = slam_pull_value ( slam, iobuf, &total_bytes ) ) != 0 )
                return rc;
-       if ( ( rc = slam_pull_value ( slam, iobuf,
-                                     &slam->block_size ) ) != 0 )
+       if ( ( rc = slam_pull_value ( slam, iobuf, &block_size ) ) != 0 )
                return rc;
 
+       /* Sanity check */
+       if ( block_size == 0 ) {
+               DBGC ( slam, "SLAM %p ignoring zero block size\n", slam );
+               return -EINVAL;
+       }
+
        /* Update the cached header */
        slam->header_len = ( iobuf->data - header );
        assert ( slam->header_len <= sizeof ( slam->header ) );
        memcpy ( slam->header, header, slam->header_len );
 
        /* Calculate number of blocks */
-       slam->num_blocks = ( ( slam->total_bytes + slam->block_size - 1 ) /
-                            slam->block_size );
-
+       slam->total_bytes = total_bytes;
+       slam->block_size = block_size;
+       slam->num_blocks = ( ( total_bytes + block_size - 1 ) / block_size );
        DBGC ( slam, "SLAM %p has total bytes %ld, block size %ld, num "
               "blocks %ld\n", slam, slam->total_bytes, slam->block_size,
               slam->num_blocks );