This is a note to let you know that I've just added the patch titled
PARISC: fix virtual aliasing issue in get_shared_area()
to the 3.0-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:
parisc-fix-virtual-aliasing-issue-in-get_shared_area.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 949a05d03490e39e773e8652ccab9157e6f595b4 Mon Sep 17 00:00:00 2001
From: James Bottomley <[email protected]>
Date: Fri, 2 Nov 2012 12:30:53 +0000
Subject: PARISC: fix virtual aliasing issue in get_shared_area()
From: James Bottomley <[email protected]>
commit 949a05d03490e39e773e8652ccab9157e6f595b4 upstream.
On Thu, 2012-11-01 at 16:45 -0700, Michel Lespinasse wrote:
> Looking at the arch/parisc/kernel/sys_parisc.c implementation of
> get_shared_area(), I do have a concern though. The function basically
> ignores the pgoff argument, so that if one creates a shared mapping of
> pages 0-N of a file, and then a separate shared mapping of pages 1-N
> of that same file, both will have the same cache offset for their
> starting address.
>
> This looks like this would create obvious aliasing issues. Am I
> misreading this ? I can't understand how this could work good enough
> to be undetected, so there must be something I'm missing here ???
This turns out to be correct and we need to pay attention to the pgoff as
well as the address when creating the virtual address for the area.
Fortunately, the bug is rarely triggered as most applications which use pgoff
tend to use large values (git being the primary one, and it uses pgoff in
multiples of 16MB) which are larger than our cache coherency modulus, so the
problem isn't often seen in practise.
Reported-by: Michel Lespinasse <[email protected]>
Signed-off-by: James Bottomley <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/parisc/kernel/sys_parisc.c | 2 ++
1 file changed, 2 insertions(+)
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -73,6 +73,8 @@ static unsigned long get_shared_area(str
struct vm_area_struct *vma;
int offset = mapping ? get_offset(mapping) : 0;
+ offset = (offset + (pgoff << PAGE_SHIFT)) & 0x3FF000;
+
addr = DCACHE_ALIGN(addr - offset) + offset;
for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
Patches currently in stable-queue which might be from
[email protected] are
queue-3.0/parisc-fix-virtual-aliasing-issue-in-get_shared_area.patch
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