9a3fe392e4
(cherry picked from commit https://lkml.org/lkml/2016/2/4/831) d07e22597d1d355 ("mm: mmap: add new /proc tunable for mmap_base ASLR") added the ability to choose from a range of values to use for entropy count in generating the random offset to the mmap_base address. The maximum value on this range was set to 32 bits for 64-bit x86 systems, but this value could be increased further, requiring more than the 32 bits of randomness provided by get_random_int(), as is already possible for arm64. Add a new function: get_random_long() which more naturally fits with the mmap usage of get_random_int() but operates exactly the same as get_random_int(). Also, fix the shifting constant in mmap_rnd() to be an unsigned long so that values greater than 31 bits generate an appropriate mask without overflow. This is especially important on x86, as its shift instruction uses a 5-bit mask for the shift operand, which meant that any value for mmap_rnd_bits over 31 acts as a no-op and effectively disables mmap_base randomization. Finally, replace calls to get_random_int() with get_random_long() where appropriate. Bug: 26963541 Signed-off-by: Daniel Cashman <dcashman@android.com> Signed-off-by: Daniel Cashman <dcashman@google.com> Change-Id: I5b45621088666d5d1dfbf43952f25ea0798b10ba |
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| Kbuild | ||