linux-kernel - RE: [RFC][PATCH 4/5] shmem: Avoid segfault in shmem_read_mapping_page

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Date:   Fri, 12 Nov 2021 12:56:50 +0000
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     Ajay Garg <ajaygargnsit@...il.com>
CC:     "ebiggers@...nel.org" <ebiggers@...nel.org>,
        "tytso@....edu" <tytso@....edu>, "corbet@....net" <corbet@....net>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "hughd@...gle.com" <hughd@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-fscrypt@...r.kernel.org" <linux-fscrypt@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC][PATCH 4/5] shmem: Avoid segfault in
 shmem_read_mapping_page_gfp()

> From: Ajay Garg [mailto:ajaygargnsit@...il.com]
> Sent: Friday, November 12, 2021 1:54 PM
> Hi Roberto.
> 
> Identical patch has been floated earlier via :
> https://lore.kernel.org/linux-
> mm/CAMZfGtUp6dkT4OWzLhL8whqNnXAbfVw5c6AQogHzY3bbM_k2Qw@...l.
> gmail.com/T/#m2189d135b9293de9b4a11362f0179c17b254d5ab

Hi Ajay

thanks, I was not aware.

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Zhong Ronghua

> Thanks and Regards,
> Ajay
> 
> On Fri, Nov 12, 2021 at 6:15 PM Roberto Sassu <roberto.sassu@...wei.com>
> wrote:
> >
> > Check the hwpoison page flag only if the page is valid in
> > shmem_read_mapping_page_gfp(). The PageHWPoison() macro tries to
> access
> > the page flags and cannot work on an error pointer.
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > ---
> >  mm/shmem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/shmem.c b/mm/shmem.c
> > index 23c91a8beb78..427863cbf0dc 100644
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -4222,7 +4222,7 @@ struct page
> *shmem_read_mapping_page_gfp(struct address_space *mapping,
> >         else
> >                 unlock_page(page);
> >
> > -       if (PageHWPoison(page))
> > +       if (!IS_ERR(page) && PageHWPoison(page))
> >                 page = ERR_PTR(-EIO);
> >
> >         return page;
> > --
> > 2.32.0
> >