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Date: Tue, 12 Feb 2008 13:28:40 +0800
From: Eugene Teo <eugeneteo@...nel.sg>
To: linux-kernel@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>, akpm@...ux-foundation.org,
torvalds@...ux-foundation.org
Subject: [PATCH] mm: tidy up follow_hugetlb_page() and get_user_pages()
This patch extends Jonathan Corbet's patch to avoid buffer overflows in
get_user_pages(). It cleans up follow_hugetlb_page(), and get_user_pages() so
that it is easier to read. It also makes sure that len and vma are validated.
Signed-off-by: Eugene Teo <eugeneteo@...nel.sg>
---
include/linux/hugetlb.h | 2 +-
mm/hugetlb.c | 13 +++----------
mm/memory.c | 39 +++++++++++++++++++++++----------------
3 files changed, 27 insertions(+), 27 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 30d606a..cf6c33e 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -19,7 +19,7 @@ static inline int is_vm_hugetlb_page(struct vm_area_struct *vma)
int hugetlb_sysctl_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *);
int hugetlb_treat_movable_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *);
int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *);
-int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, unsigned long *, int *, int, int);
+int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, unsigned long *, int, int, int);
void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long);
void __unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long);
int hugetlb_prefault(struct address_space *, struct vm_area_struct *);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1a56420..f34076f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -950,15 +950,14 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page **pages, struct vm_area_struct **vmas,
- unsigned long *position, int *length, int i,
+ unsigned long *position, int length, int i,
int write)
{
unsigned long pfn_offset;
unsigned long vaddr = *position;
- int remainder = *length;
spin_lock(&mm->page_table_lock);
- while (vaddr < vma->vm_end && remainder) {
+ for (; i < length && vaddr < vma->vm_end; ) {
pte_t *pte;
struct page *page;
@@ -977,10 +976,6 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
spin_lock(&mm->page_table_lock);
if (!(ret & VM_FAULT_ERROR))
continue;
-
- remainder = 0;
- if (!i)
- i = -EFAULT;
break;
}
@@ -997,9 +992,8 @@ same_page:
vaddr += PAGE_SIZE;
++pfn_offset;
- --remainder;
++i;
- if (vaddr < vma->vm_end && remainder &&
+ if (i < length && vaddr < vma->vm_end &&
pfn_offset < HPAGE_SIZE/PAGE_SIZE) {
/*
* We use pfn_offset to avoid touching the pageframes
@@ -1009,7 +1003,6 @@ same_page:
}
}
spin_unlock(&mm->page_table_lock);
- *length = remainder;
*position = vaddr;
return i;
diff --git a/mm/memory.c b/mm/memory.c
index 153a54b..6221b03 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -991,20 +991,23 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
int i;
unsigned int vm_flags;
+ BUG_ON(len <= 0);
+
/*
* Require read or write permissions.
* If 'force' is set, we only require the "MAY" flags.
*/
vm_flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
- i = 0;
- do {
+ for (i = 0; i < len; ) {
struct vm_area_struct *vma;
unsigned int foll_flags;
vma = find_extend_vma(mm, start);
- if (!vma && in_gate_area(tsk, start)) {
+ if (!vma)
+ goto finish_or_fault;
+ if (in_gate_area(tsk, start)) {
unsigned long pg = start & PAGE_MASK;
struct vm_area_struct *gate_vma = get_gate_vma(tsk);
pgd_t *pgd;
@@ -1012,7 +1015,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
pmd_t *pmd;
pte_t *pte;
if (write) /* user gate pages are read-only */
- return i ? : -EFAULT;
+ goto finish_or_fault;
if (pg > TASK_SIZE)
pgd = pgd_offset_k(pg);
else
@@ -1022,11 +1025,11 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
BUG_ON(pud_none(*pud));
pmd = pmd_offset(pud, pg);
if (pmd_none(*pmd))
- return i ? : -EFAULT;
+ goto finish_or_fault;
pte = pte_offset_map(pmd, pg);
if (pte_none(*pte)) {
pte_unmap(pte);
- return i ? : -EFAULT;
+ goto finish_or_fault;
}
if (pages) {
struct page *page = vm_normal_page(gate_vma, start, *pte);
@@ -1039,17 +1042,16 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
vmas[i] = gate_vma;
i++;
start += PAGE_SIZE;
- len--;
continue;
}
- if (!vma || (vma->vm_flags & (VM_IO | VM_PFNMAP))
+ if ((vma->vm_flags & (VM_IO | VM_PFNMAP))
|| !(vm_flags & vma->vm_flags))
- return i ? : -EFAULT;
+ goto finish_or_fault;
if (is_vm_hugetlb_page(vma)) {
i = follow_hugetlb_page(mm, vma, pages, vmas,
- &start, &len, i, write);
+ &start, len, i, write);
continue;
}
@@ -1061,7 +1063,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
!vma->vm_ops->fault)))
foll_flags |= FOLL_ANON;
- do {
+ for (; i < len && start < vma->vm_end; ) {
struct page *page;
/*
@@ -1082,9 +1084,9 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
foll_flags & FOLL_WRITE);
if (ret & VM_FAULT_ERROR) {
if (ret & VM_FAULT_OOM)
- return i ? i : -ENOMEM;
+ goto finish_or_oom;
else if (ret & VM_FAULT_SIGBUS)
- return i ? i : -EFAULT;
+ goto finish_or_fault;
BUG();
}
if (ret & VM_FAULT_MAJOR)
@@ -1114,10 +1116,15 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
vmas[i] = vma;
i++;
start += PAGE_SIZE;
- len--;
- } while (len && start < vma->vm_end);
- } while (len);
+ }
+ }
return i;
+
+finish_or_oom:
+ return i ? : -ENOMEM;
+
+finish_or_fault:
+ return i ? : -EFAULT;
}
EXPORT_SYMBOL(get_user_pages);
--
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