From: John Hubbard jhubbard@nvidia.com
commit f4000fdf435b8301a11cf85237c561047f8c4c72 upstream.
Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast(). This, combined with the fact that get_user_pages_fast() falls back to "slow gup", which *does* accept FOLL_FORCE, leads to an odd situation: if you need FOLL_FORCE, you cannot call get_user_pages_fast().
There does not appear to be any reason for filtering out FOLL_FORCE. There is nothing in the _fast() implementation that requires that we avoid writing to the pages. So it appears to have been an oversight.
Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
Link: http://lkml.kernel.org/r/20200107224558.2362728-9-jhubbard@nvidia.com Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags") Signed-off-by: John Hubbard jhubbard@nvidia.com Reviewed-by: Leon Romanovsky leonro@mellanox.com Reviewed-by: Jan Kara jack@suse.cz Cc: Christoph Hellwig hch@lst.de Cc: Alex Williamson alex.williamson@redhat.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Cc: Björn Töpel bjorn.topel@intel.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Dan Williams dan.j.williams@intel.com Cc: Hans Verkuil hverkuil-cisco@xs4all.nl Cc: Ira Weiny ira.weiny@intel.com Cc: Jason Gunthorpe jgg@mellanox.com Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Jens Axboe axboe@kernel.dk Cc: Jerome Glisse jglisse@redhat.com Cc: Jonathan Corbet corbet@lwn.net Cc: Kirill A. Shutemov kirill@shutemov.name Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: Mike Rapoport rppt@linux.ibm.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/gup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/gup.c +++ b/mm/gup.c @@ -2415,7 +2415,8 @@ int get_user_pages_fast(unsigned long st unsigned long addr, len, end; int nr = 0, ret = 0;
- if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM))) + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE))) return -EINVAL;
start = untagged_addr(start) & PAGE_MASK;