linux-hardening - Re: [REBASE PATCH v5 10/17] pstore: Add pstore_region

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Date:   Wed, 13 Sep 2023 16:24:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>
Cc:     corbet@....net, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        tony.luck@...el.com, gpiccoli@...lia.com,
        mathieu.poirier@...aro.org, catalin.marinas@....com,
        will@...nel.org, linus.walleij@...aro.org,
        andy.shevchenko@...il.com, vigneshr@...com, nm@...com,
        matthias.bgg@...il.com, kgene@...nel.org, alim.akhtar@...sung.com,
        bmasney@...hat.com, quic_tsoni@...cinc.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-remoteproc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, kernel@...cinc.com
Subject: Re: [REBASE PATCH v5 10/17] pstore: Add pstore_region_defined()
 helper and export it

On Mon, Sep 11, 2023 at 04:23:52PM +0530, Mukesh Ojha wrote:
> There are users like Qualcomm minidump which is interested in
> knowing the pstore frontend addresses and sizes from the backend
> (ram) to be able to register it with firmware to finally collect
> them during crash for debugging.
> 
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
>  fs/pstore/platform.c   | 15 +++++++++++++++
>  fs/pstore/ram.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pstore.h |  6 ++++++
>  3 files changed, 63 insertions(+)
> 
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index e5bca9a004cc..fdac951059c1 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -139,6 +139,21 @@ enum pstore_type_id pstore_name_to_type(const char *name)
>  }
>  EXPORT_SYMBOL_GPL(pstore_name_to_type);
>  
> +int pstore_region_defined(struct pstore_record *record,
> +			  void **virt, phys_addr_t *phys,
> +			  size_t *size, unsigned int *max_dump_cnt)
> +{
> +	if (!psinfo)
> +		return -EINVAL;
> +
> +	record->psi = psinfo;

Uh, this makes no sense to me. If this is a real pstore_record, you
cannot just assign psi here.

> +
> +	return psinfo->region_info ?
> +	       psinfo->region_info(record, virt, phys, size, max_dump_cnt) :
> +	       -EINVAL;

Common code style for this kind of thing is usually like this:

	if (!psinfo->region_info)
		return -EINVAL;

	return psinfo->region_info(...)

> +}
> +EXPORT_SYMBOL_GPL(pstore_region_defined);
> +
>  static void pstore_timer_kick(void)
>  {
>  	if (pstore_update_ms < 0)
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index ab551caa1d2a..62202f3ddf63 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -437,6 +437,47 @@ static int ramoops_pstore_erase(struct pstore_record *record)
>  	return 0;
>  }
>  
> +static int ramoops_region_info(struct pstore_record *record,
> +			       void **virt, phys_addr_t *phys,
> +			       size_t *size, unsigned int *max_dump_cnt)

But there's a larger problem here -- "virt", "phys" and likely
"max_dump_cnt" are aspects _specific to the ram backend_. This can't be
a generic pstore interface.

I'm not opposed to it being exposed only from ramoops, though.

But I think you'll want a pstore generic way to iterate over the
records...

-- 
Kees Cook