linux-kernel - Re: [PATCH] mm/gup: protect unpin_user

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Message-ID: <20200917074054.GO18329@kadam>
Date:   Thu, 17 Sep 2020 10:40:54 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     akpm@...ux-foundation.org, alex.bou9@...il.com,
        gustavoars@...nel.org, ira.weiny@...el.com, jrdr.linux@...il.com,
        linux-kernel@...r.kernel.org, madhuparnabhowmik10@...il.com,
        mporter@...nel.crashing.org, willy@...radead.org
Subject: Re: [PATCH] mm/gup: protect unpin_user_pages() against npages==-ERRNO

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@...el.com>
> Cc: Souptick Joarder <jrdr.linux@...il.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
> 
> Hi Dan,
> 
> Is is OK to use your signed-off-by here? Since you came up with this.
> 

Yeah.  That's fine.

regards,
dan carpenter