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x86/mm: Add task_size parameter to mmap_base()

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To correctly handle 32-bit and 64-bit mmap() syscalls in 64bit applications
its required to have separate address bases to place a mapping.

The tasksize can be used as an indicator to select the proper parameters
for mmap_base().

This requires the following changes:

 - Add task_size argument to mmap_base() and make the calculation based on it.
 - Provide mmap_legacy_base() as a seperate function
 - Use the new functions in arch_pick_mmap_layout()

[ tglx: Massaged changelog ]

Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: 0x7f454c46@gmail.com
Cc: linux-mm@kvack.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20170306141721.9188-3-dsafonov@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Dmitry Safonov
2017-03-06 17:17:18 +03:00
committed by Thomas Gleixner
parent 6a0b41d1e2
commit 8f3e474f3c
3 changed files with 48 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
arch/x86/mm/mmap.c
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@@ -36,25 +36,23 @@ struct va_alignment __read_mostly va_align = {
.flags = -1,
};
static unsigned long stack_maxrandom_size(void)
static inline unsigned long tasksize_32bit(void)
{
return IA32_PAGE_OFFSET;
}
static unsigned long stack_maxrandom_size(unsigned long task_size)
{
unsigned long max = 0;
if ((current->flags & PF_RANDOMIZE) &&
!(current->personality & ADDR_NO_RANDOMIZE)) {
max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
max = (-1UL) & __STACK_RND_MASK(task_size == tasksize_32bit());
max <<= PAGE_SHIFT;
}
return max;
}
/*
* Top of mmap area (just below the process stack).
*
* Leave an at least ~128 MB hole with possible stack randomization.
*/
#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
#define MAX_GAP (TASK_SIZE/6*5)
#ifdef CONFIG_COMPAT
# define mmap32_rnd_bits mmap_rnd_compat_bits
# define mmap64_rnd_bits mmap_rnd_bits
@@ -63,6 +61,8 @@ static unsigned long stack_maxrandom_size(void)
# define mmap64_rnd_bits mmap_rnd_bits
#endif
#define SIZE_128M (128 * 1024 * 1024UL)
static int mmap_is_legacy(void)
{
if (current->personality & ADDR_COMPAT_LAYOUT)
@@ -84,16 +84,30 @@ unsigned long arch_mmap_rnd(void)
return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
}
static unsigned long mmap_base(unsigned long rnd)
static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
{
unsigned long gap = rlimit(RLIMIT_STACK);
unsigned long gap_min, gap_max;
if (gap < MIN_GAP)
gap = MIN_GAP;
else if (gap > MAX_GAP)
gap = MAX_GAP;
/*
* Top of mmap area (just below the process stack).
* Leave an at least ~128 MB hole with possible stack randomization.
*/
gap_min = SIZE_128M + stack_maxrandom_size(task_size);
gap_max = (task_size / 6) * 5;
return PAGE_ALIGN(TASK_SIZE - gap - rnd);
if (gap < gap_min)
gap = gap_min;
else if (gap > gap_max)
gap = gap_max;
return PAGE_ALIGN(task_size - gap - rnd);
}
static unsigned long mmap_legacy_base(unsigned long rnd,
unsigned long task_size)
{
return __TASK_UNMAPPED_BASE(task_size) + rnd;
}
/*
@@ -107,13 +121,13 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
if (current->flags & PF_RANDOMIZE)
random_factor = arch_mmap_rnd();
mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random_factor;
mm->mmap_legacy_base = mmap_legacy_base(random_factor, TASK_SIZE);
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->mmap_base = mmap_base(random_factor, TASK_SIZE);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
}
}