mremap: don't do uneccesary checks if new_len == old_len (1d391686) · Commits · 戴 / test

The "new_len > old_len" branch in vma_to_resize() looks very confusing. It only covers the VM_DONTEXPAND/pgoff checks but everything below is equally unneeded if new_len == old_len. Change this code to return if "new_len == old_len", new_len < old_len is not possible, otherwise the code below is wrong anyway. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Acked-by:

David Rientjes <rientjes@google.com> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/mremap.c

+11 −10

Original line number	Diff line number	Diff line
		@@ -346,6 +346,7 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
		{
		struct mm_struct *mm = current->mm;
		struct vm_area_struct *vma = find_vma(mm, addr);
		unsigned long pgoff;

		if (!vma \|\| vma->vm_start > addr)
		return ERR_PTR(-EFAULT);
		@@ -357,17 +358,17 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
		if (old_len > vma->vm_end - addr)
		return ERR_PTR(-EFAULT);

		/* Need to be careful about a growing mapping */
		if (new_len > old_len) {
		unsigned long pgoff;
		if (new_len == old_len)
		return vma;

		if (vma->vm_flags & (VM_DONTEXPAND \| VM_PFNMAP))
		return ERR_PTR(-EFAULT);
		/* 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);
		}

		if (vma->vm_flags & (VM_DONTEXPAND \| VM_PFNMAP))
		return ERR_PTR(-EFAULT);

		if (vma->vm_flags & VM_LOCKED) {
		unsigned long locked, lock_limit;

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