On Mon, 2015-03-02 at 16:19 -0800, Kees Cook wrote: > This fixes the "offset2lib" weakness in ASLR for arm, arm64, mips, > powerpc, and x86. The problem is that if there is a leak of ASLR from > the executable (ET_DYN), it means a leak of shared library offset as > well (mmap), and vice versa. Further details and a PoC of this attack > are available here: > http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html > > With this patch, a PIE linked executable (ET_DYN) has its own ASLR region: > > $ ./show_mmaps_pie > 54859ccd6000-54859ccd7000 r-xp ... /tmp/show_mmaps_pie > 54859ced6000-54859ced7000 r--p ... /tmp/show_mmaps_pie > 54859ced7000-54859ced8000 rw-p ... /tmp/show_mmaps_pie Just to be clear, it's the fact that the above vmas are in a different address range to those below that shows the patch is working, right? > 7f75be764000-7f75be91f000 r-xp ... /lib/x86_64-linux-gnu/libc.so.6 > 7f75be91f000-7f75beb1f000 ---p ... /lib/x86_64-linux-gnu/libc.so.6 On powerpc I'm seeing: # /bin/dash # cat /proc/$$/maps 524e0000-52510000 r-xp 00000000 08:03 129814 /bin/dash 52510000-52520000 rw-p 00020000 08:03 129814 /bin/dash 10034f20000-10034f50000 rw-p 00000000 00:00 0 [heap] 3fffaeaf0000-3fffaeca0000 r-xp 00000000 08:03 13529 /lib/powerpc64le-linux-gnu/libc-2.19.so 3fffaeca0000-3fffaecb0000 rw-p 001a0000 08:03 13529 /lib/powerpc64le-linux-gnu/libc-2.19.so 3fffaecc0000-3fffaecd0000 rw-p 00000000 00:00 0 3fffaecd0000-3fffaecf0000 r-xp 00000000 00:00 0 [vdso] 3fffaecf0000-3fffaed20000 r-xp 00000000 08:03 13539 /lib/powerpc64le-linux-gnu/ld-2.19.so 3fffaed20000-3fffaed30000 rw-p 00020000 08:03 13539 /lib/powerpc64le-linux-gnu/ld-2.19.so 3fffc7070000-3fffc70a0000 rw-p 00000000 00:00 0 [stack] Whereas previously the /bin/dash vmas were up at 3fff.. So looks good to me for powerpc. Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> cheers
