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SubjectRe: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA


On Fri, 9 Apr 2010, Borislav Petkov wrote:
>
> Yep, looks good: its mmap_region()...

Can you double-check your current diffs - maybe something got corrupted.

mmap_region installs the vma with vma_link(), and the last thing
vma_link() does with my patch is that "anon_vma_prepare()".

Maybe with all the patches flying around, you had a reject or something,
and you lost that one anon_vma_prepare()?

Or maybe I screwed up somewhere and sent you the wrong patch. Here it is
again, just in case.

[ I have a horrible cold, and can hardly think straight. So who knows,
maybe I'm missing something. But if you have lost one of the
'anon_vma_prepare()' call sites, that would certainly explain why you
get NULL anon_vma's ]

Linus

---
mm/memory.c | 12 +++---------
mm/mmap.c | 17 ++++-------------
2 files changed, 7 insertions(+), 22 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 833952d..08d4423 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2223,9 +2223,6 @@ reuse:
gotten:
pte_unmap_unlock(page_table, ptl);

- if (unlikely(anon_vma_prepare(vma)))
- goto oom;
-
if (is_zero_pfn(pte_pfn(orig_pte))) {
new_page = alloc_zeroed_user_highpage_movable(vma, address);
if (!new_page)
@@ -2766,8 +2763,6 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
/* Allocate our own private page. */
pte_unmap(page_table);

- if (unlikely(anon_vma_prepare(vma)))
- goto oom;
page = alloc_zeroed_user_highpage_movable(vma, address);
if (!page)
goto oom;
@@ -2863,10 +2858,6 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (flags & FAULT_FLAG_WRITE) {
if (!(vma->vm_flags & VM_SHARED)) {
anon = 1;
- if (unlikely(anon_vma_prepare(vma))) {
- ret = VM_FAULT_OOM;
- goto out;
- }
page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
vma, address);
if (!page) {
@@ -3115,6 +3106,9 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
pmd_t *pmd;
pte_t *pte;

+ if (WARN_ONCE(!vma->anon_vma, "Mapping with no anon_vma"))
+ return VM_FAULT_SIGBUS;
+
__set_current_state(TASK_RUNNING);

count_vm_event(PGFAULT);
diff --git a/mm/mmap.c b/mm/mmap.c
index 75557c6..82392c2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -463,6 +463,8 @@ static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,

mm->map_count++;
validate_mm(mm);
+
+ anon_vma_prepare(vma);
}

/*
@@ -628,6 +630,8 @@ again: remove_next = 1 + (end > next->vm_end);
if (mapping)
spin_unlock(&mapping->i_mmap_lock);

+ anon_vma_prepare(vma);
+
if (remove_next) {
if (file) {
fput(file);
@@ -1674,12 +1678,6 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
if (!(vma->vm_flags & VM_GROWSUP))
return -EFAULT;

- /*
- * We must make sure the anon_vma is allocated
- * so that the anon_vma locking is not a noop.
- */
- if (unlikely(anon_vma_prepare(vma)))
- return -ENOMEM;
anon_vma_lock(vma);

/*
@@ -1720,13 +1718,6 @@ static int expand_downwards(struct vm_area_struct *vma,
{
int error;

- /*
- * We must make sure the anon_vma is allocated
- * so that the anon_vma locking is not a noop.
- */
- if (unlikely(anon_vma_prepare(vma)))
- return -ENOMEM;
-
address &= PAGE_MASK;
error = security_file_mmap(NULL, 0, 0, 0, address, 1);
if (error)

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