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.