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