[PATCH V2] mtd: gpmi: fix the NULL pointer

[Fabio Estevam]

On Mon, Nov 11, 2013 at 8:40 AM, Huang Shijie <b32955 at freescale.com> wrote:
> The imx23 board will check the fingerprint, so it will call the
> mx23_check_transcription_stamp. This function will use @chip->buffers->databuf
> as its buffer which is allocated in the nand_scan_tail().
>
> Unfortunately, the mx23_check_transcription_stamp is called before the
> nand_scan_tail(). So we will meet a NULL pointer bug:
>
> --------------------------------------------------------------------
> [    1.150000] NAND device: Manufacturer ID: 0xec, Chip ID: 0xd7 (Samsung NAND 4GiB 3,3V 8-bit), 4096MiB, page size: 4096, OOB size: 8
> [    1.160000] Unable to handle kernel NULL pointer dereference at virtual address 000005d0
> [    1.170000] pgd = c0004000
> [    1.170000] [000005d0] *pgd=00000000
> [    1.180000] Internal error: Oops: 5 [#1] ARM
> [    1.180000] Modules linked in:
> [    1.180000] CPU: 0 PID: 1 Comm: swapper Not tainted 3.12.0 #89
> [    1.180000] task: c7440000 ti: c743a000 task.ti: c743a000
> [    1.180000] PC is at memcmp+0x10/0x54
> [    1.180000] LR is at gpmi_nand_probe+0x42c/0x894
> [    1.180000] pc : [<c025fcb0>]    lr : [<c02f6a68>]    psr: 20000053
> [    1.180000] sp : c743be2c  ip : 600000d3  fp : ffffffff
> [    1.180000] r10: 000005d0  r9 : c02f5f08  r8 : 00000000
> [    1.180000] r7 : c75858a8  r6 : c75858a8  r5 : c7585b18  r4 : c7585800
> [    1.180000] r3 : 000005d0  r2 : 00000004  r1 : c05c33e4  r0 : 000005d0
> [    1.180000] Flags: nzCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
> [    1.180000] Control: 0005317f  Table: 40004000  DAC: 00000017
> [    1.180000] Process swapper (pid: 1, stack limit = 0xc743a1c0)
> --------------------------------------------------------------------
>
> This patch does two things:
>  1.) Allocates the @chip->buffers itself, and set the NAND_OWN_BUFFERS
>      for chip->options.
>  2.) Also initialize the @chip->oob_poi which is used by the
>      mx23_write_transcription_stamp(). We replace the @chip->ecc.write_page_raw
>      with chip->write_buf, since the the @chip->ecc.write_page_raw is
>      initialize in the nand_scan_tail() too. If we not do so, we will meet
>      a NULL pointer too.
>
> Cc: stable at vger.kernel.org
> Reported-by: Fabio Estevam <festevam at gmail.com>
> Signed-off-by: Huang Shijie <b32955 at freescale.com>
> ---
> v1 --> v2: do not use a local array any more.
> ---
>  drivers/mtd/nand/gpmi-nand/gpmi-nand.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> index 6e74917..a2531e7 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
> @@ -1465,7 +1465,7 @@ static int mx23_write_transcription_stamp(struct gpmi_nand_data *this)
>                 /* Write the first page of the current stride. */
>                 dev_dbg(dev, "Writing an NCB fingerprint in page 0x%x\n", page);
>                 chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
> -               chip->ecc.write_page_raw(mtd, chip, buffer, 0);
> +               chip->write_buf(mtd, buffer, mtd->writesize);
>                 chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
>
>                 /* Wait for the write to finish. */
> @@ -1609,6 +1609,12 @@ static int gpmi_init_last(struct gpmi_nand_data *this)
>         struct bch_geometry *bch_geo = &this->bch_geometry;
>         int ret;
>
> +       chip->buffers = kzalloc(sizeof(*chip->buffers), GFP_KERNEL);
> +       if (!chip->buffers)
> +               return -ENOMEM;
> +       chip->options |= NAND_OWN_BUFFERS;
> +       chip->oob_poi = chip->buffers->databuf + mtd->writesize;

It seems that this patch is making more changes than the required to
fix the NULL dereference bug.

I think that a simpler fix would be just to allocate the buffer in
mx23_check_transcription_stamp() with kzalloc.

Will submit a proposal now.

Regards,

Fabio Estevam