[31/37] mm: fix possible off-by-one in walk_pte_range()

[Greg KH]

2.6.25-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Johannes Weiner <hannes@xxxxxxxxxxxx>

commit 556637cdabcd5918c7d4a1a2679b8f86fc81e891 upstream


After the loop in walk_pte_range() pte might point to the first address after
the pmd it walks.  The pte_unmap() is then applied to something bad.

Spotted by Roel Kluin and Andreas Schwab.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxxx>
Cc: Roel Kluin <12o3l@xxxxxxxxxx>
Cc: Andreas Schwab <schwab@xxxxxxx>
Acked-by: Matt Mackall <mpm@xxxxxxxxxxx>
Acked-by: Mikael Pettersson <mikpe@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 mm/pagewalk.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -9,11 +9,15 @@ static int walk_pte_range(pmd_t *pmd, un
 	int err = 0;
 
 	pte = pte_offset_map(pmd, addr);
-	do {
+	for (;;) {
 		err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, private);
 		if (err)
 		       break;
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+		addr += PAGE_SIZE;
+		if (addr == end)
+			break;
+		pte++;
+	}
 
 	pte_unmap(pte);
 	return err;

-- 
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