[PATCH 5.17 13/75] i2c: ismt: prevent memory corruption in ismt_access()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit 690b2549b19563ec5ad53e5c82f6a944d910086e upstream.

The "data->block[0]" variable comes from the user and is a number
between 0-255.  It needs to be capped to prevent writing beyond the end
of dma_buffer[].

Fixes: 5e9a97b1f449 ("i2c: ismt: Adding support for I2C_SMBUS_BLOCK_PROC_CALL")
Reported-and-tested-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-ismt.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/i2c/busses/i2c-ismt.c
+++ b/drivers/i2c/busses/i2c-ismt.c
@@ -528,6 +528,9 @@ static int ismt_access(struct i2c_adapte
 
 	case I2C_SMBUS_BLOCK_PROC_CALL:
 		dev_dbg(dev, "I2C_SMBUS_BLOCK_PROC_CALL\n");
+		if (data->block[0] > I2C_SMBUS_BLOCK_MAX)
+			return -EINVAL;
+
 		dma_size = I2C_SMBUS_BLOCK_MAX;
 		desc->tgtaddr_rw = ISMT_DESC_ADDR_RW(addr, 1);
 		desc->wr_len_cmd = data->block[0] + 1;