HID: hidraw, fix a NULL pointer dereference in hidraw_ioctl

commit d20d5ffab92f00188f360c44c791a5ffb988247c upstream.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
IP: [<ffffffffa02c66b4>] hidraw_ioctl+0xfc/0x32c [hid]
[...]

This is reproducible by disconnecting the device while userspace does
ioctl in a loop and doesn't check return values in order to exit the
loop.

[PG: slightly/trivially reworked for backport to 34]

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index 6eadf1a9b3cca9b31e80fb231a85a56ec0393c45..0db1a0f5d2a0d21f2f5cebdaa1de68a1c6dae9d5 100644 (file)
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -243,6 +243,11 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd,
        void __user *user_arg = (void __user*) arg;
 
        lock_kernel();
+       if (!dev) {
+               ret = -ENODEV;
+               goto out;
+       }
+
        switch (cmd) {
                case HIDIOCGRDESCSIZE:
                        if (put_user(dev->hid->rsize, (int __user *)arg))
@@ -315,6 +320,7 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd,
 
                ret = -ENOTTY;
        }
+out:
        unlock_kernel();
        return ret;
 }