From: William Lee Irwin III Date: Wed, 25 May 2005 02:31:09 +0000 (-0700) Subject: [PATCH] try_to_unmap_cluster() passes out-of-bounds pte to pte_unmap() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=cafdd8ba08935d9b161bb781851dc4c0e6f70427;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git [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 --- diff --git a/mm/rmap.c b/mm/rmap.c index a6203b4e1278..9827409eb7c7 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); }