[U-Boot-Users] WARNING: in 440gx_enet.c

Roberts, John john.e.roberts at siemens.com
Fri Jun 10 14:10:32 CEST 2005

U-Boot 1.1.2
In function: int ppc_440x_eth_initialize (bd_t * bis)

This function malloc's a data structures

		/* Allocate our private use data */
		hw = (EMAC_440GX_HW_PST) malloc (sizeof (EMAC_440GX_HW_ST));

Later in function: static int ppc_440x_eth_init (struct eth_device *dev,
bd_t * bis)

	/* Free "old" buffers */
	if (hw_p->alloc_tx_buf)
		free (hw_p->alloc_tx_buf);
	if (hw_p->alloc_rx_buf)
		free (hw_p->alloc_rx_buf);

The first time through, the code assumes hw_p->alloc_tx_buf and
hw_p->alloc_rx_buf will be zero. A malloc doesn't guarantee that and the
variables are never initialized to zero. If the malloc'd memory is all "F"s
you end up with : free(0xFFFFFFFF); Or it may be any random non-zero value
you try to free.

I added a memset after the malloc to init the struct to zero. I suppose
replacing the malloc with calloc will do the trick as well.

-John Roberts

More information about the U-Boot mailing list