Commit 146608bb authored Oct 13, 2020 by John Hubbard Committed by Linus Torvalds Oct 13, 2020

mm/gup: protect unpin_user_pages() against npages==-ERRNO



As suggested by Dan Carpenter, fortify unpin_user_pages() just a bit,
against a typical caller mistake: check if the npages arg is really a
-ERRNO value, which would blow up the unpinning loop: WARN and return.

If this new WARN_ON() fires, then the system *might* be leaking pages (by
leaving them pinned), but probably not.  More likely, gup/pup returned a
hard -ERRNO error to the caller, who erroneously passed it here.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Link: https://lkml.kernel.org/r/20200917065706.409079-1-jhubbard@nvidia.com


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

parent 447f3e45

mm/gup.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -328,6 +328,13 @@ void unpin_user_pages(struct page **pages, unsigned long npages)
		{
		unsigned long index;

		/*
		* If this WARN_ON() fires, then the system might be leaking pages (by
		* leaving them pinned), but probably not. More likely, gup/pup returned
		* a hard -ERRNO error to the caller, who erroneously passed it here.
		*/
		if (WARN_ON(IS_ERR_VALUE(npages)))
		return;
		/*
		* TODO: this can be optimized for huge pages: if a series of pages is
		* physically contiguous and part of the same compound page, then a

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