Peter Xu e9119fb657 mm/gup: fix follow_devmap_p[mu]d() on page==NULL handling
This is a bug found not by any report but only by code observations.

When GUP sees a devpmd/devpud and if page==NULL is returned, it means a
fault is probably required.  Here falling through when page==NULL can
cause unexpected behavior.

Fix both cases by catching the page==NULL cases with no_page_table().

Link: https://lkml.kernel.org/r/20231123180222.1048297-1-peterx@redhat.com
Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Fixes: 080dbb618b4b ("mm/follow_page_mask: split follow_page_mask to smaller functions.")
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-12-10 16:51:52 -08:00
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2022-09-28 09:02:20 +02:00
2023-12-06 16:12:49 -08:00
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2023-12-03 18:52:56 +09:00

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.
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