Re: [PATCH V4] mtd: rawnand: qcom: fix memory corruption that causes panic

[Manivannan Sadhasivam <mani@kernel.org>]

On Mon, Apr 18, 2022 at 11:53:11AM +0530, Md Sadre Alam wrote:
> 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 or 8 based on page size.
> 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().
> 
> This patch will update nandc->max_cwperpage 1 to 4 or 8 based on page
> size in qcom_nand_attach_chip call back after freeing the previously
> allocated memory for bam txn as per nandc->max_cwperpage = 1 and then
> again allocating bam txn as per nandc->max_cwperpage = 4 or 8 based on
> page size in qcom_nand_attach_chip call back itself.
> 
> Cc: stable@vger.kernel.org
> Fixes: 6a3cec64f18c ("mtd: rawnand: qcom: convert driver to nand_scan()")
> Reported-by: Konrad Dybcio <konrad.dybcio@somainline.org>
> Signed-off-by: Md Sadre Alam <quic_mdalam@quicinc.com>
> Signed-off-by: Sricharan R <quic_srichara@quicinc.com>

I know that you and Sri were involved in creating this patch. So there should
be a co-developed-by tag for Sri and your signed-off-by should be the last one.
Like below,

Cc: stable@vger.kernel.org
Fixes: 6a3cec64f18c ("mtd: rawnand: qcom: convert driver to nand_scan()")
Reported-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Co-developed-by: Sricharan R <quic_srichara@quicinc.com>
Signed-off-by: Sricharan R <quic_srichara@quicinc.com>
Signed-off-by: Md Sadre Alam <quic_mdalam@quicinc.com>

With that,

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
> Changes in V4:
> 
>  * Incorporated "commit log wrong" comment from Mani
>  * Updated commit log
> 
> Changes in V3:
> 
>  * Incorporated "Fixes tags are missing" comment from Miquèl
>  * Added Fixes tag Fixes:6a3cec64f18c ("mtd: rawnand: qcom: convert driver to nand_scan()")
>  * Incorporated "stable tag missing" comment from Miquèl
>  * Added stable tag Cc: stable@vger.kernel.org
>  * Incorporated "Reported-by tag missing" comment from Mani
>  * Added Reported-by tag Reported-by: Konrad Dybcio <konrad.dybcio@somainline.org>
> 
> Changes in V2:
> 
>  * Incorporated "alloc_bam_transaction inside qcom_nand_attach_chip" suggestion from Mani
>  * Freed previously alloacted memory for bam txn before updating max_cwperpage inside 
>    qcom_nand_attach_chip(). 
>  * Moved alloc_bam_transaction() inside qcom_nand_attach_chip(). after upding max_cwperpage 
>    4 or 8 based on page size.
> 
>  drivers/mtd/nand/raw/qcom_nandc.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
> index 1a77542..048b255 100644
> --- a/drivers/mtd/nand/raw/qcom_nandc.c
> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
> @@ -2651,10 +2651,23 @@ static int qcom_nand_attach_chip(struct nand_chip *chip)
>  	ecc->engine_type = NAND_ECC_ENGINE_TYPE_ON_HOST;
>  
>  	mtd_set_ooblayout(mtd, &qcom_nand_ooblayout_ops);
> +	/* Free the initially allocated BAM transaction for reading the ONFI params */
> +	if (nandc->props->is_bam)
> +		free_bam_transaction(nandc);
>  
>  	nandc->max_cwperpage = max_t(unsigned int, nandc->max_cwperpage,
>  				     cwperpage);
>  
> +	/* Now allocate the BAM transaction based on updated max_cwperpage */
> +	if (nandc->props->is_bam) {
> +		nandc->bam_txn = alloc_bam_transaction(nandc);
> +		if (!nandc->bam_txn) {
> +			dev_err(nandc->dev,
> +				"failed to allocate bam transaction\n");
> +			return -ENOMEM;
> +		}
> +	}
> +
>  	/*
>  	 * 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
> @@ -2955,17 +2968,6 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
>  	if (ret)
>  		return ret;
>  
> -	if (nandc->props->is_bam) {
> -		free_bam_transaction(nandc);
> -		nandc->bam_txn = alloc_bam_transaction(nandc);
> -		if (!nandc->bam_txn) {
> -			dev_err(nandc->dev,
> -				"failed to allocate bam transaction\n");
> -			nand_cleanup(chip);
> -			return -ENOMEM;
> -		}
> -	}
> -
>  	ret = mtd_device_parse_register(mtd, probes, NULL, NULL, 0);
>  	if (ret)
>  		nand_cleanup(chip);
> -- 
> 2.7.4
>