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>
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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