This is a note to let you know that I've just added the patch titled
mm: pagewalk: call pte_hole() for VM_PFNMAP during walk_page_range
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-pagewalk-call-pte_hole-for-vm_pfnmap-during-walk_page_range.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 23aaed6659df9adfabe9c583e67a36b54e21df46 Mon Sep 17 00:00:00 2001
From: Shiraz Hashim <[email protected]>
Date: Thu, 5 Feb 2015 12:25:06 -0800
Subject: mm: pagewalk: call pte_hole() for VM_PFNMAP during walk_page_range
From: Shiraz Hashim <[email protected]>
commit 23aaed6659df9adfabe9c583e67a36b54e21df46 upstream.
walk_page_range() silently skips vma having VM_PFNMAP set, which leads
to undesirable behaviour at client end (who called walk_page_range).
Userspace applications get the wrong data, so the effect is like just
confusing users (if the applications just display the data) or sometimes
killing the processes (if the applications do something with
misunderstanding virtual addresses due to the wrong data.)
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.
Eventually userspace may get wrong pagemap data for a task.
Corresponding to a VM_PFNMAP marked vma region, kernel may report
mappings from subsequent vma regions. User space in turn may account
more pages (than really are) to the task.
In my case I was using procmem, procrack (Android utility) which uses
pagemap interface to account RSS pages of a task. Due to this bug it
was giving a wrong picture for vmas (with VM_PFNMAP set).
Fixes: a9ff785e4437 ("mm/pagewalk.c: walk_page_range should avoid VM_PFNMAP
areas")
Signed-off-by: Shiraz Hashim <[email protected]>
Acked-by: Naoya Horiguchi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/pagewalk.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -199,7 +199,10 @@ int walk_page_range(unsigned long addr,
*/
if ((vma->vm_start <= addr) &&
(vma->vm_flags & VM_PFNMAP)) {
- next = vma->vm_end;
+ if (walk->pte_hole)
+ err = walk->pte_hole(addr, next, walk);
+ if (err)
+ break;
pgd = pgd_offset(walk->mm, next);
continue;
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.18/mm-pagewalk-call-pte_hole-for-vm_pfnmap-during-walk_page_range.patch
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