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

[Miquel Raynal]

Hi Md,

quic_mdalam@xxxxxxxxxxx wrote on Thu, 14 Apr 2022 17:50:48 +0530:

> > Hi Md,
> >
> > quic_mdalam@xxxxxxxxxxx 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().

Why don't you update the sg table after increasing max_cwperpage?

> 
> >  
> >> Signed-off-by: Md Sadre Alam <quic_mdalam@xxxxxxxxxxx>
> >> Signed-off-by: Sricharan R <quic_srichara@xxxxxxxxxxx>
> >> ---
> >>   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  


Thanks,
Miquèl