[PATCH v3] i2c: xgene-slimpro: Fix out-of-bounds bug in xgene_slimpro_i2c_xfer()

[Wei Chen <harperchen1110@gmail.com>]

The data->block[0] variable comes from user and is a number between
0-255. Without proper check, the variable may be very large to cause
an out-of-bounds when performing memcpy in slimpro_i2c_blkwr.

Fix this bug by checking the value of writelen.

Fixes: f6505fbabc42 ("i2c: add SLIMpro I2C device driver on APM X-Gene platform")
Signed-off-by: Wei Chen <harperchen1110@gmail.com>
---
Changes in v2:
 - Put length check inside slimpro_i2c_blkwr
Changes in v3:
 - Correct the format of patch

 drivers/i2c/busses/i2c-xgene-slimpro.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/busses/i2c-xgene-slimpro.c b/drivers/i2c/busses/i2c-xgene-slimpro.c
index bc9a3e7e0c96..0f7263e2276a 100644
--- a/drivers/i2c/busses/i2c-xgene-slimpro.c
+++ b/drivers/i2c/busses/i2c-xgene-slimpro.c
@@ -308,6 +308,9 @@ static int slimpro_i2c_blkwr(struct slimpro_i2c_dev *ctx, u32 chip,
 	u32 msg[3];
 	int rc;
 
+	if (writelen > I2C_SMBUS_BLOCK_MAX)
+		return -EINVAL;
+
 	memcpy(ctx->dma_buffer, data, writelen);
 	paddr = dma_map_single(ctx->dev, ctx->dma_buffer, writelen,
 			       DMA_TO_DEVICE);
-- 
2.25.1