From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
vma_to_resize() is used in two locations to find and validate the vma
for the mremap location. One of the two locations already has the vma,
which is then re-found to validate the same vma.
This code can be simplified by moving the vma_lookup() from
vma_to_resize() to mremap_to() and changing the return type to an int
error.
Since the function now just validates the vma, the function is renamed
to resize_is_valid() to better reflect what it is doing.
This commit also adds documentation about the function.
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
mm/mremap.c | 53 +++++++++++++++++++++++++++++++----------------------
1 file changed, 31 insertions(+), 22 deletions(-)
diff --git a/mm/mremap.c b/mm/mremap.c
index 5917feafe8cc..e781ec4573ca 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -826,17 +826,24 @@ static unsigned long move_vma(struct vm_area_struct *vma,
return new_addr;
}
-static struct vm_area_struct *vma_to_resize(unsigned long addr,
+/*
+ * resize_is_valid() - Ensure the vma can be resized to the new length at the give
+ * address.
+ *
+ * @vma: The vma to resize
+ * @addr: The old address
+ * @old_len: The current size
+ * @new_len: The desired size
+ * @flags: The vma flags
+ *
+ * Return 0 on success, error otherwise.
+ */
+static int resize_is_valid(struct vm_area_struct *vma, unsigned long addr,
unsigned long old_len, unsigned long new_len, unsigned long flags)
{
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
unsigned long pgoff;
- vma = vma_lookup(mm, addr);
- if (!vma)
- return ERR_PTR(-EFAULT);
-
/*
* !old_len is a special case where an attempt is made to 'duplicate'
* a mapping. This makes no sense for private mappings as it will
@@ -847,37 +854,37 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
*/
if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
}
if ((flags & MREMAP_DONTUNMAP) &&
(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
/* We can't remap across vm area boundaries */
if (old_len > vma->vm_end - addr)
- return ERR_PTR(-EFAULT);
+ return -EFAULT;
if (new_len == old_len)
- return vma;
+ return 0;
/* Need to be careful about a growing mapping */
pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
pgoff += vma->vm_pgoff;
if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
- return ERR_PTR(-EFAULT);
+ return -EFAULT;
if (!mlock_future_ok(mm, vma->vm_flags, new_len - old_len))
- return ERR_PTR(-EAGAIN);
+ return -EAGAIN;
if (!may_expand_vm(mm, vma->vm_flags,
(new_len - old_len) >> PAGE_SHIFT))
- return ERR_PTR(-ENOMEM);
+ return -ENOMEM;
- return vma;
+ return 0;
}
static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
@@ -936,12 +943,16 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
old_len = new_len;
}
- vma = vma_to_resize(addr, old_len, new_len, flags);
- if (IS_ERR(vma)) {
- ret = PTR_ERR(vma);
+ vma = vma_lookup(mm, addr);
+ if (!vma) {
+ ret = -EFAULT;
goto out;
}
+ ret = resize_is_valid(vma, addr, old_len, new_len, flags);
+ if (ret)
+ goto out;
+
/* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
if (flags & MREMAP_DONTUNMAP &&
!may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
@@ -1114,11 +1125,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
/*
* Ok, we need to grow..
*/
- vma = vma_to_resize(addr, old_len, new_len, flags);
- if (IS_ERR(vma)) {
- ret = PTR_ERR(vma);
+ ret = resize_is_valid(vma, addr, old_len, new_len, flags);
+ if (ret)
goto out;
- }
/* old_len exactly to the end of the area..
*/
--
2.43.0
