From 48684a65b4e3ff544d62532c1b78962c9677b632 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Wed, 11 Feb 2015 15:28:06 -0800 Subject: mm: pagewalk: fix misbehavior of walk_page_range for vma(VM_PFNMAP) walk_page_range() silently skips vma having VM_PFNMAP set, which leads to undesirable behaviour at client end (who called walk_page_range). For example for pagemap_read(), when no callbacks are called against VM_PFNMAP vma, pagemap_read() may prepare pagemap data for next virtual address range at wrong index. That could confuse and/or break userspace applications. This patch avoid this misbehavior caused by vma(VM_PFNMAP) like follows: - for pagemap_read() which has its own ->pte_hole(), call the ->pte_hole() over vma(VM_PFNMAP), - for clear_refs and queue_pages which have their own ->tests_walk, just return 1 and skip vma(VM_PFNMAP). This is no problem because these are not interested in hole regions, - for other callers, just skip the vma(VM_PFNMAP) as a default behavior. Signed-off-by: Naoya Horiguchi Signed-off-by: Shiraz Hashim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index a36db4ad140..f5ca96524f5 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -806,6 +806,9 @@ static int clear_refs_test_walk(unsigned long start, unsigned long end, struct clear_refs_private *cp = walk->private; struct vm_area_struct *vma = walk->vma; + if (vma->vm_flags & VM_PFNMAP) + return 1; + /* * Writing 1 to /proc/pid/clear_refs affects all pages. * Writing 2 to /proc/pid/clear_refs only affects anonymous pages. -- cgit v1.2.3-70-g09d2