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mm: shift VM_GROWS* check from mmap_region() to do_mmap_pgoff() 

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" is set incorrectly.

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.

Note: we check VM_GROWS at the end to ensure that do_mmap_pgoff() won't
return EINVAL in the case when it currently returns another error code.

Many thanks to Hugh who nacked the buggy v1.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2013-09-11 14:20:18 -07:00 committed by syphyr
parent 743b977136
commit 2ff5d5555d
1 changed files with 4 additions and 6 deletions
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10
mm/mmap.c
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@ -1367,6 +1367,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
if (!file->f_op || !file->f_op->mmap)
return -ENODEV;
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
return -EINVAL;
break;
default:
@ -1375,6 +1377,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
} else {
switch (flags & MAP_TYPE) {
case MAP_SHARED:
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
return -EINVAL;
/*
* Ignore pgoff.
*/
@ -1610,11 +1614,7 @@ munmap_back:
vma->vm_pgoff = pgoff;
INIT_LIST_HEAD(&vma->anon_vma_chain);
error = -EINVAL; /* when rejecting VM_GROWSDOWN|VM_GROWSUP */
if (file) {
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
goto free_vma;
if (vm_flags & VM_DENYWRITE) {
error = deny_write_access(file);
if (error)
@ -1639,8 +1639,6 @@ munmap_back:
pgoff = vma->vm_pgoff;
vm_flags = vma->vm_flags;
} else if (vm_flags & VM_SHARED) {
if (unlikely(vm_flags & (VM_GROWSDOWN|VM_GROWSUP)))
goto free_vma;
error = shmem_zero_setup(vma);
if (error)
goto free_vma;