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

[Miquel Raynal]

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.

> 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