mm-return-an-err_ptr-from-__filemap_get_folio-fix

mm-return-an-err_ptr-from-__filemap_get_folio-fix

fix null-pointer deref

Link: https://lkml.kernel.org/r/20230310070023.GA13563@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Link: https://lkml.kernel.org/r/20230310043137.GA1624890@u2004
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>