[U-Boot] [PATCH v3 11/11] mtd: sf: Make sf_mtd.c more robust
Jagan Teki
jagan at openedev.com
Mon Nov 26 11:12:48 UTC 2018
On 26/11/18 2:12 PM, Boris Brezillon wrote:
> Hi Jagan,
>
> On Thu, 22 Nov 2018 09:40:56 +0100
> Boris Brezillon <boris.brezillon at bootlin.com> wrote:
>
>>>> + /*
>>>> + * Setting mtd->priv to NULL is the best we can do. Thanks to that,
>>>> + * the MTD layer can still call mtd hooks without risking a
>>>> + * use-after-free bug. Still, things should be fixed to prevent the
>>>> + * spi_flash object from being destroyed when del_mtd_device() fails.
>>>> + */
>>>> + sf_mtd_info.priv = NULL;
>>>> + printf("Failed to unregister MTD %s and the spi_flash object is going away: you're in deep trouble!",
>>>> + sf_mtd_info.name);
>>>
>>> Why do we need this print?
>>
>> Yes we do, just to keep the user informed that something bad happened
>> and its spi-flash is no longer usable (at least through the MTD layer).
>>
>>> can't we do the same thing in MTD core
>>> itself, so-that it can be generic for all flash objects.
>>
>> del_mtd_device() can fail, so it's the caller responsibility to decide
>> what to do when that happens. Some users will propagate the error to
>> the upper layer and maybe cancel the device removal (AFAICT,
>> driver->remove() can return an error, not sure what happens in this
>> case though). For others, like spi-flash, the device will go away, and
>> all subsequent accesses will fail.
>
> I'm about to send a new version fixing the problem I mentioned in patch
> 3, but before doing that, I'd like to know if my answer convinced you or
> if you'd still prefer this message to go away (or be placed in
> mtdcore/mtdpart.c).
I'm thinking of having the message still in MTD by showing which
interface it would belongs, along with the details.
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