FW: [PATCH] mtd: rawnand: qcom: fix memory corruption that causes panic

[Md Sadre Alam]

> Hi Md,
>
> quic_mdalam at quicinc.com wrote on Thu, 14 Apr 2022 11:09:33 +0530:
>
>> This patch fixes a memory corruption that occurred in the
>> nand_scan() path for Hynix nand device.
>>
>> On boot, for Hynix nand device will panic at a weird place:
>> | Unable to handle kernel NULL pointer dereference at virtual
>>    address 00000070
>> | [00000070] *pgd=00000000
>> | Internal error: Oops: 5 [#1] PREEMPT SMP ARM Modules linked in:
>> | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-01473-g13ae1769cfb0
>>    #38
>> | Hardware name: Generic DT based system PC is at
>> | nandc_set_reg+0x8/0x1c LR is at qcom_nandc_command+0x20c/0x5d0
>> | pc : [<c088b74c>]    lr : [<c088d9c8>]    psr: 00000113
>> | sp : c14adc50  ip : c14ee208  fp : c0cc970c
>> | r10: 000000a3  r9 : 00000000  r8 : 00000040
>> | r7 : c16f6a00  r6 : 00000090  r5 : 00000004  r4 :c14ee040
>> | r3 : 00000000  r2 : 0000000b  r1 : 00000000  r0 :c14ee040
>> | Flags: nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM Segment none
>> | Control: 10c5387d  Table: 8020406a  DAC: 00000051 Register r0
>> | information: slab kmalloc-2k start c14ee000 pointer offset
>>    64 size 2048
>> | Process swapper/0 (pid: 1, stack limit = 0x(ptrval)) nandc_set_reg
>> | from qcom_nandc_command+0x20c/0x5d0 qcom_nandc_command from
>> | nand_readid_op+0x198/0x1e8 nand_readid_op from
>> | hynix_nand_has_valid_jedecid+0x30/0x78
>> | hynix_nand_has_valid_jedecid from hynix_nand_init+0xb8/0x454
>> | hynix_nand_init from nand_scan_with_ids+0xa30/0x14a8
>> | nand_scan_with_ids from qcom_nandc_probe+0x648/0x7b0
>> | qcom_nandc_probe from platform_probe+0x58/0xac
>>
>> The problem is that the nand_scan()'s qcom_nand_attach_chip callback
>> is updating the nandc->max_cwperpage from 1 to 4.This causes the
>> sg_init_table of clear_bam_transaction() in the driver's
>> qcom_nandc_command() to memset much more than what was initially
>> allocated by alloc_bam_transaction().
> Thanks for investigating!
>
>> This patch will update nandc->max_cwperpage 1 to 4 after nand_scan()
>> returns, and remove updating nandc->max_cwperpage from
>> qcom_nand_attach_chip call back.
> The fix does not look right, as far as I understand, this should be properly handled during the attach phase. That is where we have all information about the chip and do the configuration for this chip.
>
> If you update max_cwperpage there you should probably update other internal variables that depend on it as well.

    Currently we are updating max_cwperpage  in qcom_nand_attach_chip(), 
but we are seeing issue for Hynix nand device since nand_scan_tail() is 
getting called after nand_attach() and in nand_attach() we are updating 
max_cwperpage to 4 or 8 based on page size.

     From nand_scan_tail() there is a call for nand_manufacturer_init() 
, specific to Hynix nand read_id is getting called that's why we are 
seeing this issue only for Hynix nand device. Read id sequence as below

    hynix_nand_has_valid_jedecid()

                 |

    nand_readid_op()

              |

  qcom_nandc_command()

             |

pre_command()

           |

clear_bam_transaction()   --> In this call we are doing sg_init_table() 
which is calling memset() based on max_cwperpage.Since initially we have 
allocated bam transaction as per max_cwperpage =1 and , since 
nand_chip_attach() updated max_cwperpage,  now we are doing memset as 
per max_cwperpage = 4 or 8.


So anyway we have to updated max_cwperpage after nand_scan() call only.  
Since there is no other dependency on max_cwperpage in 
nand_attach_chip() and we are using this in bam_alloc() and bam_clear().

>
>> Signed-off-by: Md Sadre Alam <quic_mdalam at quicinc.com>
>> Signed-off-by: Sricharan R <quic_srichara at quicinc.com>
>> ---
>>   drivers/mtd/nand/raw/qcom_nandc.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c
>> b/drivers/mtd/nand/raw/qcom_nandc.c
>> index 1a77542..aa3ec45 100644
>> --- a/drivers/mtd/nand/raw/qcom_nandc.c
>> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
>> @@ -2652,9 +2652,6 @@ static int qcom_nand_attach_chip(struct
>> nand_chip *chip)
>>
>>        mtd_set_ooblayout(mtd, &qcom_nand_ooblayout_ops);
>>
>> -     nandc->max_cwperpage = max_t(unsigned int, nandc->max_cwperpage,
>> -                                  cwperpage);
>> -
>>        /*
>>         * DATA_UD_BYTES varies based on whether the read/write command protects
>>         * spare data with ECC too. We protect spare data by default, so
>> we set @@ -2909,7 +2906,7 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
>>        struct nand_chip *chip = &host->chip;
>>        struct mtd_info *mtd = nand_to_mtd(chip);
>>        struct device *dev = nandc->dev;
>> -     int ret;
>> +     int ret, cwperpage;
>>
>>        ret = of_property_read_u32(dn, "reg", &host->cs);
>>        if (ret) {
>> @@ -2955,6 +2952,9 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
>>        if (ret)
>>                return ret;
>>
>> +     cwperpage = mtd->writesize / NANDC_STEP_SIZE;
>> +     nandc->max_cwperpage = max_t(unsigned int, nandc->max_cwperpage,
>> +                                  cwperpage);
>>        if (nandc->props->is_bam) {
>>                free_bam_transaction(nandc);
>>                nandc->bam_txn = alloc_bam_transaction(nandc);
>
> Thanks,
> Miquèl