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

From: Ying Han <redacted>

Fix 32bit binary get 64bit stack vma offset.

32bit binary running on 64bit system, the /proc/pid/maps shows for the
vma represents stack get a 64bit adress:
ff96c000-ff981000 rwxp 7ffffffea000 00:00 0 [stack]

Signed-off-by:  Ying Han <redacted>

fs/exec.c                     |    5 +-

diff --git a/fs/exec.c b/fs/exec.c
index 4e834f1..8c3eff4 100644
--- a/fs/exec.c
+++ b/fs/exec.c

@@ -517,6 +517,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, uns
       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);

@@ -531,7 +532,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, uns
       /*
        * 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

@@ -564,7 +565,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, uns
       /*
        * 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;
 }