Re: [PATCH] mm/gup: protect unpin_user_pages() against npages==-ERRNO

From: Dan Carpenter
Date: Thu Sep 17 2020 - 05:51:11 EST

On Wed, Sep 16, 2020 at 11:57:06PM -0700, John Hubbard wrote:
> 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@xxxxxxxxx>
> Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
> Hi Dan,
> Is is OK to use your signed-off-by here? Since you came up with this.

Yeah. That's fine.

dan carpenter