[PATCH] powerpc/mm: Handle mmap_min_addr correctly in get_unmapped_area callback

[Aneesh Kumar K.V]

After we ALIGN up the address we need to make sure we didn't overflow
and resulted in zero address. In that case, we need to make sure that
the returned address is greater than mmap_min_addr.

Also 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.

This fixes selftest va_128TBswitch --run-hugetlb reporting failures when
run as non root user for

mmap(-1, MAP_HUGETLB)
mmap(-1, MAP_HUGETLB)

We also avoid the first mmap(-1, MAP_HUGETLB) returning NULL address as mmap address
with this change

CC: Laurent Dufour <ldufour at linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
---
 arch/powerpc/mm/hugetlbpage-radix.c |  5 +++--
 arch/powerpc/mm/slice.c             | 10 ++++++----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage-radix.c b/arch/powerpc/mm/hugetlbpage-radix.c
index 2486bee0f93e..97c7a39ebc00 100644
--- a/arch/powerpc/mm/hugetlbpage-radix.c
+++ b/arch/powerpc/mm/hugetlbpage-radix.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
+#include <linux/security.h>
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
 #include <asm/cacheflush.h>
@@ -73,7 +74,7 @@ radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 	if (addr) {
 		addr = ALIGN(addr, huge_page_size(h));
 		vma = find_vma(mm, addr);
-		if (high_limit - len >= addr &&
+		if (high_limit - len >= addr && addr >= mmap_min_addr &&
 		    (!vma || addr + len <= vm_start_gap(vma)))
 			return addr;
 	}
@@ -83,7 +84,7 @@ radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 	 */
 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 	info.length = len;
-	info.low_limit = PAGE_SIZE;
+	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 	info.high_limit = mm->mmap_base + (high_limit - DEFAULT_MAP_WINDOW);
 	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
 	info.align_offset = 0;
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 06898c13901d..aec91dbcdc0b 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -32,6 +32,7 @@
 #include <linux/export.h>
 #include <linux/hugetlb.h>
 #include <linux/sched/mm.h>
+#include <linux/security.h>
 #include <asm/mman.h>
 #include <asm/mmu.h>
 #include <asm/copro.h>
@@ -377,6 +378,7 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
 	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;
@@ -393,7 +395,7 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
 	if (high_limit > DEFAULT_MAP_WINDOW)
 		addr += mm->context.slb_addr_limit - DEFAULT_MAP_WINDOW;
 
-	while (addr > PAGE_SIZE) {
+	while (addr > min_addr) {
 		info.high_limit = addr;
 		if (!slice_scan_available(addr - 1, available, 0, &addr))
 			continue;
@@ -405,8 +407,8 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
 		 * 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;
@@ -528,7 +530,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 		addr = _ALIGN_UP(addr, page_size);
 		slice_dbg(" aligned addr=%lx\n", addr);
 		/* Ignore hint if it's too large or overlaps a VMA */
-		if (addr > high_limit - len ||
+		if (addr > high_limit - len || addr < mmap_min_addr ||
 		    !slice_area_is_free(mm, addr, len))
 			addr = 0;
 	}
-- 
2.20.1