To fix 32-bit mmap() syscall returning pointer higher than 4Gb in
64-bit binaries, two mmap bases will be used: one for mapping with
32-bit syscalls and another for 64-bit syscall.
To correctly place those two bases, introduce arch_rnd() function,
which will return the random factor independently of mmap_is_ia32().
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Dmitry Safonov <dsafonov@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 d2dc0438d654..9f3ac019e51c 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -54,6 +54,14 @@ 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_64BIT
+# 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)
@@ -65,20 +73,14 @@ 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)
--
2.11.1
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