diff options
| author | Kees Cook <keescook@chromium.org> | 2015-04-15 01:47:45 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-15 02:49:05 +0300 |
| commit | 82168140bc4cec7ec9bad39705518541149ff8b7 (patch) | |
| tree | 204435faeddb6c911c8dba3313da288ccef29f55 /arch/x86/mm/mmap.c | |
| parent | fbbc400f3924ce095b466c776dc294727ec0a202 (diff) | |
| download | linux-82168140bc4cec7ec9bad39705518541149ff8b7.tar.xz | |
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: Kees Cook <keescook@chromium.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/mm/mmap.c')
| -rw-r--r-- | arch/x86/mm/mmap.c | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index df4552bd239e..ebfa52030d5c 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -67,22 +67,21 @@ static int mmap_is_legacy(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 - * 28 bits of randomness in 64bit mmaps, 40 address space bits - */ - if (current->flags & PF_RANDOMIZE) { - if (mmap_is_ia32()) - rnd = get_random_int() % (1<<8); - else - rnd = get_random_int() % (1<<28); - } + * 8 bits of randomness in 32bit mmaps, 20 address space bits + * 28 bits of randomness in 64bit mmaps, 40 address space bits + */ + if (mmap_is_ia32()) + rnd = (unsigned long)get_random_int() % (1<<8); + else + rnd = (unsigned long)get_random_int() % (1<<28); + return rnd << PAGE_SHIFT; } -static unsigned long mmap_base(void) +static unsigned long mmap_base(unsigned long rnd) { unsigned long gap = rlimit(RLIMIT_STACK); @@ -91,19 +90,19 @@ static 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); } /* * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64 * 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()) return TASK_UNMAPPED_BASE; else - return TASK_UNMAPPED_BASE + mmap_rnd(); + return TASK_UNMAPPED_BASE + rnd; } /* @@ -112,13 +111,18 @@ static unsigned long mmap_legacy_base(void) */ void arch_pick_mmap_layout(struct mm_struct *mm) { - mm->mmap_legacy_base = mmap_legacy_base(); - mm->mmap_base = mmap_base(); + unsigned long random_factor = 0UL; + + if (current->flags & PF_RANDOMIZE) + random_factor = mmap_rnd(); + + mm->mmap_legacy_base = mmap_legacy_base(random_factor); if (mmap_is_legacy()) { mm->mmap_base = mm->mmap_legacy_base; mm->get_unmapped_area = arch_get_unmapped_area; } else { + mm->mmap_base = mmap_base(random_factor); mm->get_unmapped_area = arch_get_unmapped_area_topdown; } } |