On 19.04.2018 16:49, Uwe Kleine-König wrote: > On Thu, Apr 19, 2018 at 03:29:22PM +0300, Alexander Popov wrote: >> 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 <[email protected]> >> --- >> drivers/i2c/i2c-dev.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c >> index 036a03f..5790bc8 100644 >> --- a/drivers/i2c/i2c-dev.c >> +++ b/drivers/i2c/i2c-dev.c >> @@ -280,6 +280,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client >> *client, >> */ >> if (msgs[i].flags & I2C_M_RECV_LEN) { >> if (!(msgs[i].flags & I2C_M_RD) || >> + !msgs[i].len || > > I'd prefer > > msgs[i].len > 0
Excuse me, it will be wrong. We stop if len is 0 to avoid the following ZERO_SIZE_PTR dereference. > here instead of > > !msgs[i].len I can change it to "msgs[i].len == 0". But is it really important? I've carefully tested the current version with the original repro. It works correct. > because I can parse that more easily. Semantically the patch is fine and > can have my > > Reviewed-by: Uwe Kleine-König <[email protected]> > >> msgs[i].buf[0] < 1 || >> msgs[i].len < msgs[i].buf[0] + >> I2C_SMBUS_BLOCK_MAX) { Best regards, Alexander
