Commit-ID: 6a0b41d1e23dd3318568461593ae5e36d966981e
Gitweb: http://git.kernel.org/tip/6a0b41d1e23dd3318568461593ae5e36d966981e
Author: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
AuthorDate: Mon, 6 Mar 2017 17:17:17 +0300
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 13 Mar 2017 14:59:22 +0100
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@xxxxxxxxxxxxx>
Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
Cc: 0x7f454c46@xxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170306141721.9188-2-dsafonov@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/x86/mm/mmap.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 7940166..f31ed70 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)
--
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