On Sun, 14 Jul 2013 18:54:51 +0200 Oleg Nesterov <o...@redhat.com> wrote:
> mmap() doesn't allow the non-anonymous mappings with VM_GROWS* bit set. > In particular this means that mmap_region()->vma_merge(file, vm_flags) > must always fail if vm_flags & VM_GROWS. So it does not make sense to > check VM_GROWS* after we already allocated the new vma, the only caller, > do_mmap_pgoff(), which can pass this flag can do the check itself. > > And this looks a bit more correct, mmap_region() already unmapped the > old mapping at this stage. But if mmap() is going to fail, it should > avoid do_munmap() if possible. > > ... > > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1327,6 +1327,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned > long addr, > } > } > > + /* Only MAP_PRIVATE|MAP_ANONYMOUS can use MAP_GROWS */ > + if ((vm_flags & VM_MAYSHARE) && (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))) That is of course vm_flags&(VM_MAYSHARE|VM_GROWSDOWN|VM_GROWSUP), but that perhaps is less clear. > + return -EINVAL; I had to stare for a while but yes, the change looks OK to me. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/