This is a note to let you know that I've just added the patch titled
mm: avoid setting up anonymous pages into file mapping
to the 4.1-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-avoid-setting-up-anonymous-pages-into-file-mapping.patch
and it can be found in the queue-4.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6b7339f4c31ad69c8e9c0b2859276e22cf72176d Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Mon, 6 Jul 2015 23:18:37 +0300
Subject: mm: avoid setting up anonymous pages into file mapping
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
commit 6b7339f4c31ad69c8e9c0b2859276e22cf72176d upstream.
Reading page fault handler code I've noticed that under right
circumstances kernel would map anonymous pages into file mappings: if
the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated
on ->mmap(), kernel would handle page fault to not populated pte with
do_anonymous_page().
Let's change page fault handler to use do_anonymous_page() only on
anonymous VMA (->vm_ops == NULL) and make sure that the VMA is not
shared.
For file mappings without vm_ops->fault() or shred VMA without vm_ops,
page fault on pte_none() entry would lead to SIGBUS.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2669,6 +2669,10 @@ static int do_anonymous_page(struct mm_s
pte_unmap(page_table);
+ /* File mapping without ->vm_ops ? */
+ if (vma->vm_flags & VM_SHARED)
+ return VM_FAULT_SIGBUS;
+
/* Check if we need to add a guard page to the stack */
if (check_stack_guard_page(vma, address) < 0)
return VM_FAULT_SIGSEGV;
@@ -3097,6 +3101,9 @@ static int do_fault(struct mm_struct *mm
- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
pte_unmap(page_table);
+ /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
+ if (!vma->vm_ops->fault)
+ return VM_FAULT_SIGBUS;
if (!(flags & FAULT_FLAG_WRITE))
return do_read_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
@@ -3242,13 +3249,12 @@ static int handle_pte_fault(struct mm_st
barrier();
if (!pte_present(entry)) {
if (pte_none(entry)) {
- if (vma->vm_ops) {
- if (likely(vma->vm_ops->fault))
- return do_fault(mm, vma, address, pte,
- pmd, flags, entry);
- }
- return do_anonymous_page(mm, vma, address,
- pte, pmd, flags);
+ if (vma->vm_ops)
+ return do_fault(mm, vma, address, pte, pmd,
+ flags, entry);
+
+ return do_anonymous_page(mm, vma, address, pte, pmd,
+ flags);
}
return do_swap_page(mm, vma, address,
pte, pmd, flags, entry);
Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-4.1/mm-avoid-setting-up-anonymous-pages-into-file-mapping.patch
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