linux-kernel - [PATCH 5/5] mm/vmalloc.c: avoid endless loop under v[un]mapping improper ranges

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Date:   Wed, 21 Sep 2016 12:34:21 +0800
From:   zijun_hu <zijun_hu@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, zijun_hu@....com,
        tj@...nel.org, mingo@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, mgorman@...hsingularity.net
Subject: [PATCH 5/5] mm/vmalloc.c: avoid endless loop under v[un]mapping
 improper ranges

From: zijun_hu <zijun_hu@....com>

fix the following bug:
 - endless loop maybe happen when v[un]mapping improper ranges
   whose either boundary is not aligned to page

Signed-off-by: zijun_hu <zijun_hu@....com>
---
 mm/vmalloc.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5eeecc3..16fe957 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -67,7 +67,7 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
 	do {
 		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
 		WARN_ON(!pte_none(ptent) && !pte_present(ptent));
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+	} while (pte++, addr += PAGE_SIZE, addr < end && addr >= PAGE_SIZE);
 }
 
 static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end)
@@ -108,6 +108,9 @@ static void vunmap_page_range(unsigned long addr, unsigned long end)
 	unsigned long next;
 
 	BUG_ON(addr >= end);
+	WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
+
+	addr = round_down(addr, PAGE_SIZE);
 	pgd = pgd_offset_k(addr);
 	do {
 		next = pgd_addr_end(addr, end);
@@ -139,7 +142,7 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr,
 			return -ENOMEM;
 		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
 		(*nr)++;
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+	} while (pte++, addr += PAGE_SIZE, addr < end);
 	return 0;
 }
 
@@ -193,6 +196,8 @@ static int vmap_page_range_noflush(unsigned long start, unsigned long end,
 	int nr = 0;
 
 	BUG_ON(addr >= end);
+	BUG_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
+
 	pgd = pgd_offset_k(addr);
 	do {
 		next = pgd_addr_end(addr, end);
-- 
1.9.1