[PATCH 3.2 108/140] i2c: core-smbus: prevent stack corruption on read I2C_BLOCK_DATA

Ben Hutchings
2018-02-28T17:36:29Z

From: Jeremy Compostella <jeremy.compostella@intel.com>

commit 89c6efa61f5709327ecfa24bff18e57a4e80c7fa upstream.

On a I2C_SMBUS_I2C_BLOCK_DATA read request, if data->block[0] is
greater than I2C_SMBUS_BLOCK_MAX + 1, the underlying I2C driver writes
data out of the msgbuf1 array boundary.

It is possible from a user application to run into that issue by
calling the I2C_SMBUS ioctl with data.block[0] greater than
I2C_SMBUS_BLOCK_MAX + 1.

This patch makes the code compliant with
Documentation/i2c/dev-interface by raising an error when the requested
size is larger than 32 bytes.

Call Trace:
[<ffffffff8139f695>] dump_stack+0x67/0x92
[<ffffffff811802a4>] panic+0xc5/0x1eb
[<ffffffff810ecb5f>] ? vprintk_default+0x1f/0x30
[<ffffffff817456d3>] ? i2cdev_ioctl_smbus+0x303/0x320
[<ffffffff8109a68b>] __stack_chk_fail+0x1b/0x20
[<ffffffff817456d3>] i2cdev_ioctl_smbus+0x303/0x320
[<ffffffff81745aed>] i2cdev_ioctl+0x4d/0x1e0
[<ffffffff811f761a>] do_vfs_ioctl+0x2ba/0x490
[<ffffffff81336e43>] ? security_file_ioctl+0x43/0x60
[<ffffffff811f7869>] SyS_ioctl+0x79/0x90
[<ffffffff81a22e97>] entry_SYSCALL_64_fastpath+0x12/0x6a

Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/i2c/i2c-core.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -2009,16 +2009,17 @@ static s32 i2c_smbus_xfer_emulated(struc
the underlying bus driver */
break;
case I2C_SMBUS_I2C_BLOCK_DATA:
+ if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
+ dev_err(&adapter->dev, "Invalid block %s size %d\n",
+ read_write == I2C_SMBUS_READ ? "read" : "write",
+ data->block[0]);
+ return -EINVAL;
+ }
+
if (read_write == I2C_SMBUS_READ) {
msg[1].len = data->block[0];
} else {
msg[0].len = data->block[0] + 1;
- if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
- dev_err(&adapter->dev,
- "Invalid block write size %d\n",
- data->block[0]);
- return -EINVAL;
- }
for (i = 1; i <= data->block[0]; i++)
msgbuf0[i] = data->block[i];
}