Commit 82168140 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds

x86: 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 extracts the checking of
PF_RANDOMIZE.
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fbbc400f
...@@ -67,22 +67,21 @@ static int mmap_is_legacy(void) ...@@ -67,22 +67,21 @@ static int mmap_is_legacy(void)
static unsigned long mmap_rnd(void) static unsigned long mmap_rnd(void)
{ {
unsigned long rnd = 0; unsigned long rnd;
/* /*
* 8 bits of randomness in 32bit mmaps, 20 address space bits * 8 bits of randomness in 32bit mmaps, 20 address space bits
* 28 bits of randomness in 64bit mmaps, 40 address space bits * 28 bits of randomness in 64bit mmaps, 40 address space bits
*/ */
if (current->flags & PF_RANDOMIZE) { if (mmap_is_ia32())
if (mmap_is_ia32()) rnd = (unsigned long)get_random_int() % (1<<8);
rnd = get_random_int() % (1<<8); else
else rnd = (unsigned long)get_random_int() % (1<<28);
rnd = get_random_int() % (1<<28);
}
return rnd << PAGE_SHIFT; return rnd << PAGE_SHIFT;
} }
static unsigned long mmap_base(void) static unsigned long mmap_base(unsigned long rnd)
{ {
unsigned long gap = rlimit(RLIMIT_STACK); unsigned long gap = rlimit(RLIMIT_STACK);
...@@ -91,19 +90,19 @@ static unsigned long mmap_base(void) ...@@ -91,19 +90,19 @@ static unsigned long mmap_base(void)
else if (gap > MAX_GAP) else if (gap > MAX_GAP)
gap = MAX_GAP; gap = MAX_GAP;
return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); return PAGE_ALIGN(TASK_SIZE - gap - rnd);
} }
/* /*
* Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64 * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
* does, but not when emulating X86_32 * does, but not when emulating X86_32
*/ */
static unsigned long mmap_legacy_base(void) static unsigned long mmap_legacy_base(unsigned long rnd)
{ {
if (mmap_is_ia32()) if (mmap_is_ia32())
return TASK_UNMAPPED_BASE; return TASK_UNMAPPED_BASE;
else else
return TASK_UNMAPPED_BASE + mmap_rnd(); return TASK_UNMAPPED_BASE + rnd;
} }
/* /*
...@@ -112,13 +111,18 @@ static unsigned long mmap_legacy_base(void) ...@@ -112,13 +111,18 @@ static unsigned long mmap_legacy_base(void)
*/ */
void arch_pick_mmap_layout(struct mm_struct *mm) void arch_pick_mmap_layout(struct mm_struct *mm)
{ {
mm->mmap_legacy_base = mmap_legacy_base(); unsigned long random_factor = 0UL;
mm->mmap_base = mmap_base();
if (current->flags & PF_RANDOMIZE)
random_factor = mmap_rnd();
mm->mmap_legacy_base = mmap_legacy_base(random_factor);
if (mmap_is_legacy()) { if (mmap_is_legacy()) {
mm->mmap_base = mm->mmap_legacy_base; mm->mmap_base = mm->mmap_legacy_base;
mm->get_unmapped_area = arch_get_unmapped_area; mm->get_unmapped_area = arch_get_unmapped_area;
} else { } else {
mm->mmap_base = mmap_base(random_factor);
mm->get_unmapped_area = arch_get_unmapped_area_topdown; mm->get_unmapped_area = arch_get_unmapped_area_topdown;
} }
} }
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