| Message ID | 20220204020010.68930-2-jhubbard@nvidia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/gup: some cleanups | expand |
On Thu, Feb 03, 2022 at 06:00:06PM -0800, John Hubbard wrote: > From: Peter Xu <peterx@redhat.com> > > Alex reported invalid page pointer returned with pin_user_pages_remote() from > vfio after upstream commit 4b6c33b32296 ("vfio/type1: Prepare for batched > pinning with struct vfio_batch"). This commit message uses overly long lines all over. Otherwise looks good: Reviewed-by: Christoph Hellwig <hch@lst.de>
On Thu 03-02-22 18:00:06, John Hubbard wrote: > From: Peter Xu <peterx@redhat.com> > > Alex reported invalid page pointer returned with pin_user_pages_remote() from > vfio after upstream commit 4b6c33b32296 ("vfio/type1: Prepare for batched > pinning with struct vfio_batch"). > > It turns out that it's not the fault of the vfio commit; however after vfio > switches to a full page buffer to store the page pointers it starts to expose > the problem easier. > > The problem is for VM_PFNMAP vmas we should normally fail with an -EFAULT then > vfio will carry on to handle the MMIO regions. However when the bug triggered, > follow_page_mask() returned -EEXIST for such a page, which will jump over the > current page, leaving that entry in **pages untouched. However the caller is > not aware of it, hence the caller will reference the page as usual even if the > pointer data can be anything. > > We had that -EEXIST logic since commit 1027e4436b6a ("mm: make GUP handle pfn > mapping unless FOLL_GET is requested") which seems very reasonable. It could > be that when we reworked GUP with FOLL_PIN we could have overlooked that > special path in commit 3faa52c03f44 ("mm/gup: track FOLL_PIN pages"), even if > that commit rightfully touched up follow_devmap_pud() on checking FOLL_PIN when > it needs to return an -EEXIST. > > Attaching the Fixes to the FOLL_PIN rework commit, as it happened later than > 1027e4436b6a. > > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Jan Kara <jack@suse.cz> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages") > Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > Reported-by: Alex Williamson <alex.williamson@redhat.com> > Debugged-by: Alex Williamson <alex.williamson@redhat.com> > Tested-by: Alex Williamson <alex.williamson@redhat.com> > Signed-off-by: Peter Xu <peterx@redhat.com> > [jhubbard: added some tags, removed a reference to an out of tree module.] > Signed-off-by: John Hubbard <jhubbard@nvidia.com> Makes sence. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > mm/gup.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/gup.c b/mm/gup.c > index a9d4d724aef7..80229ecf0114 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -465,7 +465,7 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, > pte_t *pte, unsigned int flags) > { > /* No page to get reference */ > - if (flags & FOLL_GET) > + if (flags & (FOLL_GET | FOLL_PIN)) > return -EFAULT; > > if (flags & FOLL_TOUCH) { > -- > 2.35.1 >
On 2/3/22 23:25, Christoph Hellwig wrote: > On Thu, Feb 03, 2022 at 06:00:06PM -0800, John Hubbard wrote: >> From: Peter Xu <peterx@redhat.com> >> >> Alex reported invalid page pointer returned with pin_user_pages_remote() from >> vfio after upstream commit 4b6c33b32296 ("vfio/type1: Prepare for batched >> pinning with struct vfio_batch"). > > This commit message uses overly long lines all over. I'll reflow it to 72 columns and post a v5 with the full set of reviewed-by tags. > > Otherwise looks good: > > Reviewed-by: Christoph Hellwig <hch@lst.de> I appreciate the reviews, from you and everyone, as always. thanks,
diff --git a/mm/gup.c b/mm/gup.c index a9d4d724aef7..80229ecf0114 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -465,7 +465,7 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, pte_t *pte, unsigned int flags) { /* No page to get reference */ - if (flags & FOLL_GET) + if (flags & (FOLL_GET | FOLL_PIN)) return -EFAULT; if (flags & FOLL_TOUCH) {