linux-kernel - Re: [PATCH] pstore: Avoid to write records with null size

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Date:   Tue, 12 Feb 2019 12:07:34 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Yue Hu <huyue2@...ong.com>
Cc:     Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore: Avoid to write records with null size

On Thu, Jan 31, 2019 at 6:26 PM Yue Hu <huyue2@...ong.com> wrote:
>
> From 57cb7141b227b7f75a6e4afb8319f803510cc07f Mon Sep 17 00:00:00 2001
> From: Yue Hu <huyue2@...ong.com>
> Date: Thu, 31 Jan 2019 18:12:46 +0800
> Subject: [PATCH] pstore: Avoid to write records with null size
>
> Sometimes pstore_console_write() will write record with null size
> to persistent ram zone, that is unnecessary. It will only increase
> resource consumtion. ramoops_write_kmsg_hdr() has same logic if
> null hdr happened. So let's avoid those cases.
>
> Signed-off-by: Yue Hu <huyue2@...ong.com>
> ---
>  fs/pstore/platform.c | 3 +++
>  fs/pstore/ram.c      | 6 ++++--
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index 7486e48..5e9b817 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -504,6 +504,9 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
>  {
>         struct pstore_record record;
>
> +       if (!c)
> +               return;
> +
>         pstore_record_init(&record, psinfo);
>         record.type = PSTORE_TYPE_CONSOLE;
>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 0bb086b..7e188f6 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -364,8 +364,10 @@ static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz,
>                 (time64_t)record->time.tv_sec,
>                 record->time.tv_nsec / 1000,
>                 record->compressed ? 'C' : 'D');
> -       WARN_ON_ONCE(!hdr);
> -       len = hdr ? strlen(hdr) : 0;
> +       if (WARN_ON_ONCE(!hdr))
> +               return 0;
> +
> +       len = strlen(hdr);
>         persistent_ram_write(prz, hdr, len);
>         kfree(hdr);

Applied, thanks!

-- 
Kees Cook