linux-kernel - [PATCH] sparc64: Fix hugepage page table free

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Date:   Mon, 17 Apr 2017 15:46:41 -0700
From:   Nitin Gupta <nitin.m.gupta@...cle.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Nitin Gupta <nitin.m.gupta@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Ingo Molnar <mingo@...nel.org>, sparclinux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] sparc64: Fix hugepage page table free

Make sure the start adderess is aligned to PMD_SIZE
boundary when freeing page table backing a hugepage
region. The issue was causing segfaults when a region
backed by 64K pages was unmapped since such a region
is in general not PMD_SIZE aligned.

Signed-off-by: Nitin Gupta <nitin.m.gupta@...cle.com>
---
 arch/sparc/mm/hugetlbpage.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
index ee5273a..7c29d38 100644
--- a/arch/sparc/mm/hugetlbpage.c
+++ b/arch/sparc/mm/hugetlbpage.c
@@ -461,6 +461,22 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb,
 	pgd_t *pgd;
 	unsigned long next;
 
+	addr &= PMD_MASK;
+	if (addr < floor) {
+		addr += PMD_SIZE;
+		if (!addr)
+			return;
+	}
+	if (ceiling) {
+		ceiling &= PMD_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		end -= PMD_SIZE;
+	if (addr > end - 1)
+		return;
+
 	pgd = pgd_offset(tlb->mm, addr);
 	do {
 		next = pgd_addr_end(addr, end);
-- 
2.9.2