mm: shift VM_GROWS* check from mmap_region() to do_mmap_pgoff()
authorOleg Nesterov <oleg@redhat.com>
Wed, 11 Sep 2013 21:20:18 +0000 (14:20 -0700)
committerDanny Wood <danwood76@gmail.com>
Thu, 28 Jan 2021 09:32:01 +0000 (09:32 +0000)
commit475069d6426ba9cd7f21886bfe7da352ec6d5582
tree6c63a12db3b27d48307cfa392a0139c17fdb65f0
parent7fbac9c3a4a687bf5fb64b252d4deee7fab8ae02
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>
Change-Id: Ic81c1919adf051b9308125fcb87ae6a46e71b580
mm/mmap.c