Our client confirmed that the more he fetches the more memory is consumed.
The segfault was indeed caused by the absence of LDR_CNTRL.
The tests show that:
* without LDR_CNTRL, we reach 256Mb and segfault ;
* with LDR_CNTRL=MAXDATA=0x10000000, we reach 256Mo but there is no
segfault, the program just continues running ;
* with LDR_CNTRL=MAXDATA=0x80000000, we reach 2Go and there is no segfault
either, the program just continues running.