From cafdd8ba08935d9b161bb781851dc4c0e6f70427 Mon Sep 17 00:00:00 2001 From: William Lee Irwin III Date: Tue, 24 May 2005 19:31:09 -0700 Subject: [PATCH] [PATCH] try_to_unmap_cluster() passes out-of-bounds pte to pte_unmap() 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/rmap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index a6203b4e12..9827409eb7 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -626,7 +626,7 @@ static void try_to_unmap_cluster(unsigned long cursor, 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; @@ -658,7 +658,7 @@ static void try_to_unmap_cluster(unsigned long cursor, 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)) @@ -694,7 +694,7 @@ static void try_to_unmap_cluster(unsigned long cursor, (*mapcount)--; } - pte_unmap(pte); + pte_unmap(original_pte); out_unlock: spin_unlock(&mm->page_table_lock); } -- 2.39.5