linux-kernel - Re: [PATCH] mtd: nand: fix NULL pointer dereference in of_get_nand_ecc

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Date:	Tue, 26 Apr 2016 21:57:31 +0200
From:	Rafał Miłecki <zajec5@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	Richard Weinberger <richard@....at>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: nand: fix NULL pointer dereference in of_get_nand_ecc_algo

On 26 April 2016 at 20:53, Boris Brezillon
<boris.brezillon@...e-electrons.com> wrote:
> On Tue, 26 Apr 2016 20:36:16 +0200
> Rafał Miłecki <zajec5@...il.com> wrote:
>
>> Our array nand_ecc_algos doesn't specify mappings for all available
>> enum nand_ecc_algo values. The one missing there is NAND_ECC_UNKNOWN
>> as this value is reserved for algorithm not being specified at all.
>> It means we have to be careful when iterating this array and handle
>> NULL values.
>>
>> Signed-off-by: Rafał Miłecki <zajec5@...il.com>
>> ---
>> Hi Boris,
>>
>> Sorry for this crash in nand subsystem :( If you think it's OK you may
>> pick this patch as a fixup for
>> c6e002a7ca9f ("mtd: nand: add support for "nand-ecc-algo" DT property")
>> ---
>>  drivers/mtd/nand/nand_base.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
>> index a5417a0..0eaa9dc 100644
>> --- a/drivers/mtd/nand/nand_base.c
>> +++ b/drivers/mtd/nand/nand_base.c
>> @@ -4016,6 +4016,8 @@ static int of_get_nand_ecc_algo(struct device_node *np)
>>       err = of_property_read_string(np, "nand-ecc-algo", &pm);
>>       if (!err) {
>>               for (i = 0; i < ARRAY_SIZE(nand_ecc_algos); i++)
>> +                     if (!nand_ecc_algos[i])
>> +                             continue;
>
> Can we add an "unknown" entry, or start iterating at NAND_ECC_HAMMING
> or NAND_ECC_UNKNOWN + 1 instead of adding this extra test?

Sure, if you think it's better. I'll send V2.

-- 
Rafał