[PATCH 3.16 085/129] powerpc/mm/hash: Handle mmap_min_addr correctly in get_unmapped_area topdown search

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>

commit 3b4d07d2674f6b4a9281031f99d1f7efd325b16d upstream.

When doing top-down search the low_limit is not PAGE_SIZE but rather
max(PAGE_SIZE, mmap_min_addr). This handle cases in which mmap_min_addr >
PAGE_SIZE.

Fixes: fba2369e6ceb ("mm: use vm_unmapped_area() on powerpc architecture")
Reviewed-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/powerpc/mm/slice.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -30,6 +30,7 @@
 #include <linux/err.h>
 #include <linux/spinlock.h>
 #include <linux/export.h>
+#include <linux/security.h>
 #include <asm/mman.h>
 #include <asm/mmu.h>
 #include <asm/spu.h>
@@ -313,6 +314,7 @@ static unsigned long slice_find_area_top
 	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
 	unsigned long addr, found, prev;
 	struct vm_unmapped_area_info info;
+	unsigned long min_addr = max(PAGE_SIZE, mmap_min_addr);
 
 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 	info.length = len;
@@ -320,7 +322,7 @@ static unsigned long slice_find_area_top
 	info.align_offset = 0;
 
 	addr = mm->mmap_base;
-	while (addr > PAGE_SIZE) {
+	while (addr > min_addr) {
 		info.high_limit = addr;
 		if (!slice_scan_available(addr - 1, available, 0, &addr))
 			continue;
@@ -332,8 +334,8 @@ static unsigned long slice_find_area_top
 		 * Check if we need to reduce the range, or if we can
 		 * extend it to cover the previous available slice.
 		 */
-		if (addr < PAGE_SIZE)
-			addr = PAGE_SIZE;
+		if (addr < min_addr)
+			addr = min_addr;
 		else if (slice_scan_available(addr - 1, available, 0, &prev)) {
 			addr = prev;
 			goto prev_slice;
@@ -415,7 +417,7 @@ unsigned long slice_get_unmapped_area(un
 		addr = _ALIGN_UP(addr, 1ul << pshift);
 		slice_dbg(" aligned addr=%lx\n", addr);
 		/* Ignore hint if it's too large or overlaps a VMA */
-		if (addr > mm->task_size - len ||
+		if (addr > mm->task_size - len || addr < mmap_min_addr ||
 		    !slice_area_is_free(mm, addr, len))
 			addr = 0;
 	}