You can use the set variable (gdb) and the assign (dbx) commands to alter the contents of memory specified by an address as shown in the following example:
GDB Mode
(idb) set variable $address = &(node->_data)
(idb) print $address
$11 = (int *) 0x805c500
(idb) print *(int *)($address)
$12 = -32
(idb) set variable *(int *)($address) = 1024
(idb) print *(int *)($address)
$13 = 1024
DBX Mode
(idb) set $address = &(node->_data)
(idb) print $address
0x805c500
(idb) print *(int *)($address)
-32
(idb) assign *(int *)($address) = 1024
(idb) print *(int *)($address)
1024
See also