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authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2015-02-12 00:28:06 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-12 02:06:06 +0100
commit48684a65b4e3ff544d62532c1b78962c9677b632 (patch)
tree884da0dc303b41042c9928b40ef7ae651d34e22d /fs/proc/task_mmu.c
parentmempolicy: apply page table walker on queue_pages_range() (diff)
downloadlinux-48684a65b4e3ff544d62532c1b78962c9677b632.tar.xz
linux-48684a65b4e3ff544d62532c1b78962c9677b632.zip
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 <n-horiguchi@ah.jp.nec.com> Signed-off-by: Shiraz Hashim <shashim@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc/task_mmu.c')
-rw-r--r--fs/proc/task_mmu.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index a36db4ad140b..f5ca96524f5f 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.