[PATCH] i2c: mv64xxx: prevent illegal pointer access

[PATCH] i2c: mv64xxx: prevent illegal pointer access

[enachman]

From: Elad Nachman <enachman@marvell.com>

Spurious interrupts left while i2c controller still
at RX or TX state would try to access the RX or TX
buffer pointer, which is NULL.
Add check to verify buffer pointer is not NULL before
reading or writing the buffer for additional TX or RX
operations.

Signed-off-by: Elad Nachman <enachman@marvell.com>
---
 drivers/i2c/busses/i2c-mv64xxx.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index 8fc26a511320..e6baa9c520b4 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -390,14 +390,18 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
 		break;
 
 	case MV64XXX_I2C_ACTION_SEND_DATA:
-		writel(drv_data->msg->buf[drv_data->byte_posn++],
-			drv_data->reg_base + drv_data->reg_offsets.data);
+		if (drv_data->msg && drv_data->msg->buf)
+			writel(drv_data->msg->buf[drv_data->byte_posn++],
+				drv_data->reg_base + drv_data->reg_offsets.data);
 		writel(drv_data->cntl_bits,
 			drv_data->reg_base + drv_data->reg_offsets.control);
 		break;
 
 	case MV64XXX_I2C_ACTION_RCV_DATA:
-		drv_data->msg->buf[drv_data->byte_posn++] =
+		if (drv_data->msg && drv_data->msg->buf)
+			drv_data->msg->buf[drv_data->byte_posn++] =
+				readl(drv_data->reg_base + drv_data->reg_offsets.data);
+		else
 			readl(drv_data->reg_base + drv_data->reg_offsets.data);
 		writel(drv_data->cntl_bits,
 			drv_data->reg_base + drv_data->reg_offsets.control);
-- 
2.25.1

Re: [PATCH] i2c: mv64xxx: prevent illegal pointer access

[Markus Elfring]

…
> Add check to verify buffer pointer is not NULL before
> reading or writing the buffer for additional TX or RX
> operations.

You may occasionally put more than 53 characters into text lines
of such a change description.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.16#n658

Regards,
Markus