Commit 96e1fac1 authored Nov 13, 2020 by Jason Gunthorpe Committed by Linus Torvalds Nov 14, 2020

mm/gup: use unpin_user_pages() in __gup_longterm_locked()



When FOLL_PIN is passed to __get_user_pages() the page list must be put
back using unpin_user_pages() otherwise the page pin reference persists
in a corrupted state.

There are two places in the unwind of __gup_longterm_locked() that put
the pages back without checking.  Normally on error this function would
return the partial page list making this the caller's responsibility,
but in these two cases the caller is not allowed to see these pages at
all.

Fixes: 3faa52c0 ("mm/gup: track FOLL_PIN pages")
Reported-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/0-v2-3ae7d9d162e2+2a7-gup_cma_fix_jgg@nvidia.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 22e4663e

mm/gup.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -1647,6 +1647,9 @@ check_again:
		/*
		* drop the above get_user_pages reference.
		*/
		if (gup_flags & FOLL_PIN)
		unpin_user_pages(pages, nr_pages);
		else
		for (i = 0; i < nr_pages; i++)
		put_page(pages[i]);

		@@ -1728,6 +1731,9 @@ static long __gup_longterm_locked(struct mm_struct *mm,
		goto out;

		if (check_dax_vmas(vmas_tmp, rc)) {
		if (gup_flags & FOLL_PIN)
		unpin_user_pages(pages, rc);
		else
		for (i = 0; i < rc; i++)
		put_page(pages[i]);
		rc = -EOPNOTSUPP;

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