[PATCH] i2c: powermac: Fix out-of-bounds bug in i2c_powermac_smbus_xfer

[Alex Guo]

The data->block[0] variable comes from user. Without proper check,
the variable may be very large to cause an out-of-bounds bug.

Fix this bug by checking the value of data->block[0] first.

Similar commit:
1. commit 39244cc7548 ("i2c: ismt: Fix an out-of-bounds bug in
ismt_access()")
2. commit 92fbb6d1296 ("i2c: xgene-slimpro: Fix out-of-bounds
bug in xgene_slimpro_i2c_xfer()")

Signed-off-by: Alex Guo <alexguo1023 at gmail.com>
---
 drivers/i2c/busses/i2c-powermac.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/i2c/busses/i2c-powermac.c b/drivers/i2c/busses/i2c-powermac.c
index f99a2cc721a8..3a061b67716a 100644
--- a/drivers/i2c/busses/i2c-powermac.c
+++ b/drivers/i2c/busses/i2c-powermac.c
@@ -78,10 +78,14 @@ static s32 i2c_powermac_smbus_xfer(	struct i2c_adapter*	adap,
 	 * anywhere near a pmac i2c bus anyway ...
 	 */
         case I2C_SMBUS_BLOCK_DATA:
+		if (data->block[0] < 1 || data->block[0] > I2C_SMBUS_BLOCK_MAX)
+			return -EINVAL;
 		buf = data->block;
 		len = data->block[0] + 1;
 		break;
 	case I2C_SMBUS_I2C_BLOCK_DATA:
+		if (data->block[0] < 1 || data->block[0] > I2C_SMBUS_BLOCK_MAX)
+			return -EINVAL;
 		buf = &data->block[1];
 		len = data->block[0];
 		break;
-- 
2.34.1