Messages in this thread Patch in this message | | | From | John Hubbard <> | Subject | [PATCH] mm/gup: protect unpin_user_pages() against npages==-ERRNO | Date | Wed, 16 Sep 2020 23:57:06 -0700 |
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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.
Cc: Ira Weiny <ira.weiny@intel.com> Cc: Souptick Joarder <jrdr.linux@gmail.com> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: John Hubbard <jhubbard@nvidia.com> ---
Hi Dan,
Is is OK to use your signed-off-by here? Since you came up with this.
thanks, John Hubbard NVIDIA
mm/gup.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c index e5739a1974d5..41d082707016 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -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 -- 2.28.0
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