i2c: bail out early when RDWR parameters are wrong

The buggy parameters currently get caught later, but emit a noisy WARN.
Userspace should not be able to trigger this, so add similar checks much
earlier. Also avoids some unneeded code paths, of course. Apply kernel
coding stlye to a comment while here.

Reported-by: syzbot+ffb0b3ffa6cfbc7d7b3f@syzkaller.appspotmail.com
Tested-by: syzbot+ffb0b3ffa6cfbc7d7b3f@syzkaller.appspotmail.com
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 6ceb11cc4be182ba1d4dfa52fe993cabaa0a093f..6ef38a8ee95cb22ff7c6d0bc25a09c5c61b39752 100644 (file)
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -440,8 +440,13 @@ static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                                   sizeof(rdwr_arg)))
                        return -EFAULT;
 
-               /* Put an arbitrary limit on the number of messages that can
-                * be sent at once */
+               if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
+                       return -EINVAL;
+
+               /*
+                * Put an arbitrary limit on the number of messages that can
+                * be sent at once
+                */
                if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
                        return -EINVAL;