try_to_unmap_cluster() does:
for (pte = pte_offset_map(pmd, address);
address < end; pte++, address += PAGE_SIZE) {
...
}
pte_unmap(pte);
It may take a little staring to notice, but pte can actually fall off the
end of the pte page in this iteration, which makes life difficult for
kmap_atomic() and the users not expecting it to BUG(). Of course, we're
somewhat lucky in that arithmetic elsewhere in the function guarantees that
at least one iteration is made, lest this force larger rearrangements to be
made. This issue and patch also apply to non-mm mainline and with trivial
adjustments, at least two related kernels.
Discovered during internal testing at Oracle.
Signed-off-by: William Irwin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
--- gregkh-2.6.11.10.orig/mm/rmap.c 2005-05-16 10:51:55.000000000 -0700
+++ gregkh-2.6.11.10/mm/rmap.c 2005-05-26 22:01:49.000000000 -0700
@@ -641,7 +641,7 @@
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
- pte_t *pte;
+ pte_t *pte, *original_pte;
pte_t pteval;
struct page *page;
unsigned long address;
@@ -673,7 +673,7 @@
if (!pmd_present(*pmd))
goto out_unlock;
- for (pte = pte_offset_map(pmd, address);
+ for (original_pte = pte = pte_offset_map(pmd, address);
address < end; pte++, address += PAGE_SIZE) {
if (!pte_present(*pte))
@@ -710,7 +710,7 @@
(*mapcount)--;
}
- pte_unmap(pte);
+ pte_unmap(original_pte);
out_unlock:
spin_unlock(&mm->page_table_lock);
-
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