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authorPeter Xu <peterx@redhat.com>2022-03-22 14:39:37 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 15:57:01 -0700
commit7196040e19ad634293acd3eff7083149d7669031 (patch)
tree0941fd2a4f7b1f8b33ddec63131199b56c1f200a /mm/gup.c
parentc0226eb8bde854e016a594a16f5c0d98aca426fa (diff)
mm: fix invalid page pointer returned with FOLL_PIN gups
Patch series "mm/gup: some cleanups", v5. This patch (of 5): 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. [jhubbard@nvidia.com: added some tags, removed a reference to an out of tree module.] Link: https://lkml.kernel.org/r/20220207062213.235127-1-jhubbard@nvidia.com Link: https://lkml.kernel.org/r/20220204020010.68930-1-jhubbard@nvidia.com Link: https://lkml.kernel.org/r/20220204020010.68930-2-jhubbard@nvidia.com Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages") Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: John Hubbard <jhubbard@nvidia.com> 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> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: David Hildenbrand <david@redhat.com> Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 7bc1ba9ce440..41da0bd61bec 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) {