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| author | Dmitry Safonov <dsafonov@virtuozzo.com> | 2017-03-06 15:17:17 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2017-03-13 14:59:22 +0100 |
| commit | 6a0b41d1e23dd3318568461593ae5e36d966981e (patch) | |
| tree | 001fd5d265883cf33a50ba36dbbd68d7f0b825b4 /arch/x86/mm | |
| parent | Linux 4.11-rc2 (diff) | |
| download | linux-6a0b41d1e23dd3318568461593ae5e36d966981e.tar.xz linux-6a0b41d1e23dd3318568461593ae5e36d966981e.zip | |
x86/mm: Introduce arch_rnd() to compute 32/64 mmap random base
The compat (32bit) mmap() sycall issued by a 64-bit task results in a
mapping above 4GB. That's outside the compat mode address space and
prevents CRIU to restore 32bit processes from a 64bit application.
As a first step to address this, split out the address base randomizing
calculation from arch_mmap_rnd() into a helper function, which can be used
independent of mmap_ia32() based decisions.
[ tglx: Massaged changelog ]
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
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/20170306141721.9188-2-dsafonov@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/mm')
| -rw-r--r-- | arch/x86/mm/mmap.c | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 7940166c799b..f31ed7097d0b 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -55,6 +55,14 @@ static unsigned long stack_maxrandom_size(void) #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 +#else +# define mmap32_rnd_bits mmap_rnd_bits +# define mmap64_rnd_bits mmap_rnd_bits +#endif + static int mmap_is_legacy(void) { if (current->personality & ADDR_COMPAT_LAYOUT) @@ -66,20 +74,14 @@ static int mmap_is_legacy(void) return sysctl_legacy_va_layout; } -unsigned long arch_mmap_rnd(void) +static unsigned long arch_rnd(unsigned int rndbits) { - unsigned long rnd; - - if (mmap_is_ia32()) -#ifdef CONFIG_COMPAT - rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); -#else - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); -#endif - else - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); + return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT; +} - return rnd << PAGE_SHIFT; +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) |