powerpc: Ensure random space between stack and mmaps
get_random_int() returns the same value within a 1 jiffy interval. This means that the mmap and stack regions will almost always end up the same distance apart, making a relative offset based attack possible. To fix this, shift the randomness we use for the mmap region by 1 bit. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Родитель
912f9ee21c
Коммит
a5adc91a4b
|
@ -46,6 +46,14 @@ static inline int mmap_is_legacy(void)
|
|||
return sysctl_legacy_va_layout;
|
||||
}
|
||||
|
||||
/*
|
||||
* Since get_random_int() returns the same value within a 1 jiffy window,
|
||||
* we will almost always get the same randomisation for the stack and mmap
|
||||
* region. This will mean the relative distance between stack and mmap will
|
||||
* be the same.
|
||||
*
|
||||
* To avoid this we can shift the randomness by 1 bit.
|
||||
*/
|
||||
static unsigned long mmap_rnd(void)
|
||||
{
|
||||
unsigned long rnd = 0;
|
||||
|
@ -53,11 +61,11 @@ static unsigned long mmap_rnd(void)
|
|||
if (current->flags & PF_RANDOMIZE) {
|
||||
/* 8MB for 32bit, 1GB for 64bit */
|
||||
if (is_32bit_task())
|
||||
rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
|
||||
rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT)));
|
||||
else
|
||||
rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
|
||||
rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT)));
|
||||
}
|
||||
return rnd << PAGE_SHIFT;
|
||||
return (rnd << PAGE_SHIFT) * 2;
|
||||
}
|
||||
|
||||
static inline unsigned long mmap_base(void)
|
||||
|
|
Загрузка…
Ссылка в новой задаче