Re: [PATCH] mtd: gpmi-nand: Fix kernel crash due to missing verify_buf

Huang Shijie
2012-08-11T03:01:35Z

On Fri, Aug 10, 2012 at 6:48 PM, Fabio Estevam <festevam@gmail.com> wrote:
> From: Fabio Estevam <fabio.estevam@freescale.com>
>
> When selecting CONFIG_MTD_NAND_VERIFY_WRITE=y and doing simple write tests the following kernel crash happens:
>
> root@freescale /$ dd if=/dev/zero of=/dev/mtd0 bs=128k count=1
> [ 41.070000] Unable to handle kernel NULL pointer dereference at virtual addr0
> [ 41.080000] pgd = c77ac000
> [ 41.080000] [00000000] *pgd=4773c831, *pte=00000000, *ppte=00000000
> [ 41.090000] Internal error: Oops: 17 [#1] ARM
> [ 41.090000] Modules linked in:
> [ 41.090000] CPU: 0 Not tainted (3.6.0-rc1-next-20120809-00002-ga25d017-d)
> [ 41.090000] PC is at nand_verify_buf+0x18/0x5c
> [ 41.090000] LR is at nand_write_page+0xc0/0x140
> [ 41.090000] pc : [<c023e7d4>] lr : [<c023fcfc>] psr: 20000013
> [ 41.090000] sp : c7779de4 ip : 00000000 fp : c6e60000
> [ 41.090000] r10: 00000000 r9 : 00020000 r8 : 00000000
> [ 41.090000] r7 : 00000000 r6 : c6e60000 r5 : c762cb10 r4 : 00000000
> [ 41.090000] r3 : c762c8a8 r2 : 00000800 r1 : c6e60000 r0 : 00000000
> [ 41.090000] Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
> [ 41.090000] Control: 0005317f Table: 477ac000 DAC: 00000015
> [ 41.090000] Process dd (pid: 427, stack limit = 0xc7778270)
> [ 41.090000] Stack: (0xc7779de4 to 0xc777a000)
> ...
>
> The NULL pointer dereference that happens in nand_verify_buf() is due to the missing
> gpmi_verify_buf implementation in the gpmi-nand driver.
>
> Implement gpmi_verify_buf() to prevent this crash.
>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Huang Shijie <b32955@freescale.com>
> Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
> ---
> drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 18 ++++++++++++++++++
> drivers/mtd/nand/gpmi-nand/gpmi-nand.h | 1 +
> 2 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> index 8c0d2f0..72b25ce 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> @@ -1533,6 +1533,23 @@ void gpmi_nfc_exit(struct gpmi_nand_data *this)
> gpmi_free_dma_buffer(this);
> }
>
> +static int gpmi_verify_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
> +{
> + struct nand_chip *nand = mtd->priv;
> + struct gpmi_nand_data *data = container_of(mtd, struct gpmi_nand_data,
> + mtd);
> + int ret;
> +
> + ret = nand->ecc.read_page(mtd, nand, data->verify_buf, 0, 0);
> + if (ret)
> + return -EFAULT;
> +
> + if (memcmp(buf, data->verify_buf, len))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> static int __devinit gpmi_nfc_init(struct gpmi_nand_data *this)
> {
> struct mtd_info *mtd = &this->mtd;
> @@ -1555,6 +1572,7 @@ static int __devinit gpmi_nfc_init(struct gpmi_nand_data *this)
> chip->dev_ready = gpmi_dev_ready;
> chip->read_byte = gpmi_read_byte;
> chip->read_buf = gpmi_read_buf;
> + chip->verify_buf = gpmi_verify_buf;
> chip->write_buf = gpmi_write_buf;
> chip->ecc.read_page = gpmi_ecc_read_page;
> chip->ecc.write_page = gpmi_ecc_write_page;
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
> index 1547a60..cd9bdf7 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
> @@ -148,6 +148,7 @@ struct gpmi_nand_data {
> /* General-use Variables */
> int current_chip;
> unsigned int command_length;
> + uint8_t verify_buf[NAND_MAX_PAGESIZE];
It seems this will waste a page memory when the nand page is 4K.
So it's better to allocate the verify_buf dynamically whose size is
the mtd->writesize.

Best Regards
Huang Shijie

>
> /* passed from upper layer */
> uint8_t *upper_buf;
> --
> 1.7.1
>