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

[Fabio Estevam]

From: Fabio Estevam <fabio.estevam at freescale.com>

When selecting CONFIG_MTD_NAND_VERIFY_WRITE=y and doing simple write tests the following kernel crash happens:

root at 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 at vger.kernel.org>
Signed-off-by: Huang Shijie <b32955 at freescale.com>
Signed-off-by: Fabio Estevam <fabio.estevam at 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];
 
 	/* passed from upper layer */
 	uint8_t			*upper_buf;
-- 
1.7.1