Re: [PATCH]Fix: 32bit binary has 64bit address of stack vma

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 12 Jan 2009 15:05:51 -0800
Mike Waychison <mikew@google.com> wrote:

> > Subject: fs/exec.c: fix value of vma->vm_pgoff for the stack VMA of 32-bit processes
> > From: Ying Han <yinghan@google.com>
> > 
> > With a 32 bit binary running on a 64 bit system, the /proc/pid/maps for
> > the [stack] VMA displays a 64-bit address:
> > 
> > ff96c000-ff981000 rwxp 7ffffffea000 00:00 0 [stack]
> > 
> > This is because vma->vm_pgoff for that VMA is incorrectly being stored in
> > units of offset-in-bytes.  It should be stored in units of offset-in-pages.
> > 
> 
> The problem is that the offset was stored without taking into account 
> the shift.

Sigh.  Is it efficient to have me sitting here reverse-engineering the
code, writing your changelog?



From: Ying Han <yinghan@google.com>

With a 32 bit binary running on a 64 bit system, the /proc/pid/maps for
the [stack] VMA displays a 64-bit address:

ff96c000-ff981000 rwxp 7ffffffea000 00:00 0 [stack]

This is because vma->vm_pgoff for that VMA is not being updated for the
shift of the stack VMA.

Signed-off-by: Ying Han <yinghan@google.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/exec.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff -puN fs/exec.c~fs-execc-fix-value-of-vma-vm_pgoff-for-the-stack-vma-of-32-bit-processes fs/exec.c
--- a/fs/exec.c~fs-execc-fix-value-of-vma-vm_pgoff-for-the-stack-vma-of-32-bit-processes
+++ a/fs/exec.c
@@ -509,6 +509,7 @@ static int shift_arg_pages(struct vm_are
 	unsigned long length = old_end - old_start;
 	unsigned long new_start = old_start - shift;
 	unsigned long new_end = old_end - shift;
+	unsigned long new_pgoff = new_start >> PAGE_SHIFT;
 	struct mmu_gather *tlb;
 
 	BUG_ON(new_start > new_end);
@@ -523,7 +524,7 @@ static int shift_arg_pages(struct vm_are
 	/*
 	 * cover the whole range: [new_start, old_end)
 	 */
-	vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
+	vma_adjust(vma, new_start, old_end, new_pgoff, NULL);
 
 	/*
 	 * move the page tables downwards, on failure we rely on
@@ -556,7 +557,7 @@ static int shift_arg_pages(struct vm_are
 	/*
 	 * shrink the vma to just the new range.
 	 */
-	vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
+	vma_adjust(vma, new_start, new_end, new_pgoff, NULL);
 
 	return 0;
 }
_

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