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powerpc: standardize mmap_rnd() usage 

In preparation for splitting out ET_DYN ASLR, this refactors the use of
mmap_rnd() to be used similarly to arm and x86.

(Can mmap ASLR be safely enabled in the legacy mmap case here?  Other
archs use "mm->mmap_base = TASK_UNMAPPED_BASE + random_factor".)

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kees Cook 2015-04-14 15:47:54 -07:00 committed by Linus Torvalds
parent 1f0569df0b
commit ed6322746a
1 changed files with 15 additions and 11 deletions
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26
arch/powerpc/mm/mmap.c
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@ -55,19 +55,18 @@ static inline int mmap_is_legacy(void)
static unsigned long mmap_rnd(void)
{
unsigned long rnd = 0;
unsigned long rnd;
/* 8MB for 32bit, 1GB for 64bit */
if (is_32bit_task())
rnd = (unsigned long)get_random_int() % (1<<(23-PAGE_SHIFT));
else
rnd = (unsigned long)get_random_int() % (1<<(30-PAGE_SHIFT));
if (current->flags & PF_RANDOMIZE) {
/* 8MB for 32bit, 1GB for 64bit */
if (is_32bit_task())
rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
else
rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
}
return rnd << PAGE_SHIFT;
}
static inline unsigned long mmap_base(void)
static inline unsigned long mmap_base(unsigned long rnd)
{
unsigned long gap = rlimit(RLIMIT_STACK);
@ -76,7 +75,7 @@ static inline unsigned long mmap_base(void)
else if (gap > MAX_GAP)
gap = MAX_GAP;
return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
return PAGE_ALIGN(TASK_SIZE - gap - rnd);
}
/*
@ -85,6 +84,11 @@ static inline unsigned long mmap_base(void)
*/
void arch_pick_mmap_layout(struct mm_struct *mm)
{
unsigned long random_factor = 0UL;
if (current->flags & PF_RANDOMIZE)
random_factor = mmap_rnd();
/*
* Fall back to the standard layout if the personality
* bit is set, or if the expected stack growth is unlimited:
@ -93,7 +97,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
mm->mmap_base = TASK_UNMAPPED_BASE;
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
mm->mmap_base = mmap_base();
mm->mmap_base = mmap_base(random_factor);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
}
}