[PATCH 1/2] mmap: arch_get_unmapped_area(): use proper mmap base for bottom up direction

[Heiko Carstens]

This is more or less the generic variant of 41aacc1eea "x86 get_unmapped_area:
Access mmap_legacy_base through mm_struct member".

So effectively architectures which use an own arch_pick_mmap_layout()
implementation but call the generic arch_get_unmapped_area() now can also
randomize their mmap_base.

All architectures which have an own arch_pick_mmap_layout() and call
the generic arch_get_unmapped_area() (arm64, s390, tile) currently set
mmap_base to TASK_UNMAPPED_BASE. This is also true for the generic
arch_pick_mmap_layout() function. So this change is a no-op currently.

Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
---
 mm/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 9d54851..fa206ab 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1872,7 +1872,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 
 	info.flags = 0;
 	info.length = len;
-	info.low_limit = TASK_UNMAPPED_BASE;
+	info.low_limit = mm->mmap_base;
 	info.high_limit = TASK_SIZE;
 	info.align_mask = 0;
 	return vm_unmapped_area(&info);
-- 
1.8.3.4

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