81fc8f90b8
commit 93b0d9178743a68723babe8448981f658aebc58e upstream. mfill_atomic_install_pte() checks page->mapping to detect whether one page is used in the page cache. However as pointed out by Matthew, the page can logically be a tail page rather than always the head in the case of uffd minor mode with UFFDIO_CONTINUE. It means we could wrongly install one pte with shmem thp tail page assuming it's an anonymous page. It's not that clear even for anonymous page, since normally anonymous pages also have page->mapping being setup with the anon vma. It's safe here only because the only such caller to mfill_atomic_install_pte() is always passing in a newly allocated page (mcopy_atomic_pte()), whose page->mapping is not yet setup. However that's not extremely obvious either. For either of above, use page_mapping() instead. Link: https://lkml.kernel.org/r/Y2K+y7wnhC4vbnP2@x1n Fixes: 153132571f02 ("userfaultfd/shmem: support UFFDIO_CONTINUE for shmem") Signed-off-by: Peter Xu <peterx@redhat.com> Reported-by: Matthew Wilcox <willy@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.