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SubjectRe: [PATCH 4/9] mtd: nand: qcom: fix null pointer access for erased buffer detection
On 2018-04-10 14:42, Miquel Raynal wrote:
> Hi Abhishek,
>
> On Wed, 4 Apr 2018 18:12:20 +0530, Abhishek Sahu
> <absahu@codeaurora.org> wrote:
>
>> parse_read_errors can be called with only oob buf also in which
>> case data_buf will be NULL. If data_buf is NULL, then don’t
>> treat this page as completely erased in case of ECC uncorrectable
>> error.
>>
>> Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
>> ---
>> drivers/mtd/nand/qcom_nandc.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/qcom_nandc.c
>> b/drivers/mtd/nand/qcom_nandc.c
>> index 57c16a6..0ebcc55 100644
>> --- a/drivers/mtd/nand/qcom_nandc.c
>> +++ b/drivers/mtd/nand/qcom_nandc.c
>> @@ -1607,9 +1607,11 @@ static int parse_read_errors(struct
>> qcom_nand_host *host, u8 *data_buf,
>> if (host->bch_enabled) {
>> erased = (erased_cw & ERASED_CW) == ERASED_CW ?
>> true : false;
>
> Why the parse_read_errors() function could not be called without
> data_buf when using BCH? Are you sure the situation can only happen
> without it?
>

host->bch_enabled case is different where controller itself tells
regarding erased page in status register.

> Would the following apply here too, with a:
>

erased_chunk_check_and_fixup will be used only for 4 bit RS ECC
code in which there is no support from HW for erased page detection
and we need to check few data bytes value.

Thanks,
Abhishek

> if (!data_buf) {
> erased = false;
> } else {
> if (host->bch_enabled)
> ...
> else
> ...
> }
>
>> - } else {
>> + } else if (data_buf) {
>> erased = erased_chunk_check_and_fixup(data_buf,
>> data_len);
>> + } else {
>> + erased = false;
>> }
>>
>> if (erased) {
>> @@ -1652,7 +1654,8 @@ static int parse_read_errors(struct
>> qcom_nand_host *host, u8 *data_buf,
>> max_bitflips = max(max_bitflips, stat);
>> }
>>
>> - data_buf += data_len;
>> + if (data_buf)
>> + data_buf += data_len;
>> if (oob_buf)
>> oob_buf += oob_len + ecc->bytes;
>> }
>
> Thanks,
> Miquèl

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