From: Alexander Popov alex.popov@linux.com
commit 23a27722b5292ef0b27403c87a109feea8296a5c upstream.
i2cdev_ioctl_rdwr() allocates i2c_msg.buf using memdup_user(), which returns ZERO_SIZE_PTR if i2c_msg.len is zero.
Currently i2cdev_ioctl_rdwr() always dereferences the buf pointer in case of I2C_M_RD | I2C_M_RECV_LEN transfer. That causes a kernel oops in case of zero len.
Let's check the len against zero before dereferencing buf pointer.
This issue was triggered by syzkaller.
Signed-off-by: Alexander Popov alex.popov@linux.com Reviewed-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de [wsa: use '< 1' instead of '!' for easier readability] Signed-off-by: Wolfram Sang wsa@the-dreams.de [Harshit: backport to 4.14.y, use rdwr_pa[i].len instead of msgs[i].len as the 4.14.y code uses rdwr_pa.] Signed-off-by: Harshit Mogalapalli harshit.m.mogalapalli@oracle.com --- Conflicts: drivers/i2c/i2c-dev.c - use rdwr_pa[i].len instead of msgs[i].len Since a NULL pointer dereference happens on 4.14.y this backport patch will fix the issue. --- drivers/i2c/i2c-dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index b7f9fb00f695..08aff5ebc99a 100644 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -297,7 +297,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client, */ if (rdwr_pa[i].flags & I2C_M_RECV_LEN) { if (!(rdwr_pa[i].flags & I2C_M_RD) || - rdwr_pa[i].buf[0] < 1 || + rdwr_pa[i].len < 1 || rdwr_pa[i].buf[0] < 1 || rdwr_pa[i].len < rdwr_pa[i].buf[0] + I2C_SMBUS_BLOCK_MAX) { i++;