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

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Message-ID: <CAHP4M8V9i7PZvPKwzWRo54u0xjrGwhtPPsHCjxwy9SLQM7HbEg@mail.gmail.com>
Date:   Fri, 12 Nov 2021 18:23:43 +0530
From:   Ajay Garg <ajaygargnsit@...il.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     ebiggers@...nel.org, tytso@....edu, corbet@....net,
        viro@...iv.linux.org.uk, hughd@...gle.com,
        akpm@...ux-foundation.org, linux-fscrypt@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 4/5] shmem: Avoid segfault in shmem_read_mapping_page_gfp()

Hi Roberto.

Identical patch has been floated earlier via :
https://lore.kernel.org/linux-mm/CAMZfGtUp6dkT4OWzLhL8whqNnXAbfVw5c6AQogHzY3bbM_k2Qw@mail.gmail.com/T/#m2189d135b9293de9b4a11362f0179c17b254d5ab


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
>