BACKPORT: FROMGIT: mm: always lock new vma before inserting into vma tree

While it's not strictly necessary to lock a newly created vma before
adding it into the vma tree (as long as no further changes are performed
to it), it seems like a good policy to lock it and prevent accidental
changes after it becomes visible to the page faults. Lock the vma before
adding it into the vma tree.

Link: https://lkml.kernel.org/r/20230804152724.3090321-6-surenb@google.com


Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit c3249c06c48dda30f93e62b57773d5ed409d4f77
https: //git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)
[surenb: resolved conflicts due to changes in vma_merge() and
__vma_adjust()]

Bug: 293665307
Change-Id: I4ee0d2abcc8a3f45545f470f1bf7f0be728d6f44
Signed-off-by: Suren Baghdasaryan <surenb@google.com>