A security issue in Linux ASLR implementation which affects some AMD processors has been found. The issue affects to all Linux process even if they are not using shared libraries (statically compiled). The problem appears because some mmapped objects (VDSO, libraries, etc.) are poorly randomized in an attempt to avoid cache aliasing penalties for AMD Bulldozer (Family 15h) processors. Affected systems have reduced the mmapped files entropy by eight. Grsecurity/PaX is also affected. The total entropy for the VVAR/VDSO, mmapped files and libraries of a processes are reduced by eight. The number of possible locations where the mapped areas can be placed are reduced by 87.5%.
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