x86 get_unmapped_area: Access mmap_legacy_base through mm_struct member

commit 41aacc1eea645c99edbe8fbcf78a97dc9b862adc upstream.

This is the updated version of df54d6fa5427 ("x86 get_unmapped_area():
use proper mmap base for bottom-up direction") that only randomizes the
mmap base address once.

Signed-off-by: Radu Caragea <sinaelgl@gmail.com>
Reported-and-tested-by: Jeff Shorey <shoreyjeff@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Adrian Sendroiu <molecula2788@gmail.com>
Cc: Greg KH <greg@kroah.com>
Cc: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index 0514890..cdb2fc9 100644 (file)
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -115,7 +115,7 @@ static void find_start_end(unsigned long flags, unsigned long *begin,
                                *begin = new_begin;
                }
        } else {
-               *begin = TASK_UNMAPPED_BASE;
+               *begin = current->mm->mmap_legacy_base;
                *end = TASK_SIZE;
        }
 }

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 845df68..5c1ae28 100644 (file)
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -112,12 +112,14 @@ static unsigned long mmap_legacy_base(void)
  */
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
+       mm->mmap_legacy_base = mmap_legacy_base();
+       mm->mmap_base = mmap_base();
+
        if (mmap_is_legacy()) {
-               mm->mmap_base = mmap_legacy_base();
+               mm->mmap_base = mm->mmap_legacy_base;
                mm->get_unmapped_area = arch_get_unmapped_area;
                mm->unmap_area = arch_unmap_area;
        } else {
-               mm->mmap_base = mmap_base();
                mm->get_unmapped_area = arch_get_unmapped_area_topdown;
                mm->unmap_area = arch_unmap_area_topdown;
        }

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5b42f1b..de3a321 100644 (file)
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -297,6 +297,7 @@ struct mm_struct {
        void (*unmap_area) (struct mm_struct *mm, unsigned long addr);
 #endif
        unsigned long mmap_base;                /* base of mmap area */
+       unsigned long mmap_legacy_base;         /* base of mmap area in bottom-up allocations */
        unsigned long task_size;                /* size of task vm space */
        unsigned long cached_hole_size;         /* if non-zero, the largest hole below free_area_cache */
        unsigned long free_area_cache;          /* first hole of size cached_hole_size or larger */