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| author | Oleg Nesterov <oleg@redhat.com> | 2015-09-04 15:48:10 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-09-04 16:54:41 -0700 |
| commit | 1d3916869798755968b3cd764ab21f2bb86ffff7 (patch) | |
| tree | d8a9baa17fab65069a49000cfe4c741982f1ccfe | |
| parent | d456fb9e5254df433d4806769d7ff75d80d66aa4 (diff) | |
| download | lwn-1d3916869798755968b3cd764ab21f2bb86ffff7.tar.gz lwn-1d3916869798755968b3cd764ab21f2bb86ffff7.zip | |
mremap: don't do uneccesary checks if new_len == old_len
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>
| -rw-r--r-- | mm/mremap.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/mm/mremap.c b/mm/mremap.c index 7dcf7b42068e..d3f42bece564 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -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); + if (new_len == old_len) + return vma; + /* Need to be careful about a growing mapping */ - if (new_len > old_len) { - unsigned long pgoff; - - if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) - return ERR_PTR(-EFAULT); - pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; - pgoff += vma->vm_pgoff; - if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) - return ERR_PTR(-EINVAL); - } + 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; |