HID: hidraw, fix a NULL pointer dereference in hidraw_write

commit e42dee9a99a3ecd32b5c027e8f7411fb5bc11eb6 upstream.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
IP: [<ffffffffa0f0a625>] hidraw_write+0x3b/0x116 [hid]
[...]

This is reproducible by disconnecting the device while userspace writes
to dev node 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 0db1a0f5d2a0d21f2f5cebdaa1de68a1c6dae9d5..9d3c663dc8f44bc1da209137e21100e79b24eee3 100644 (file)
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -106,11 +106,15 @@ out:
 static ssize_t hidraw_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
 {
        unsigned int minor = iminor(file->f_path.dentry->d_inode);
-       /* FIXME: What stops hidraw_table going NULL */
-       struct hid_device *dev = hidraw_table[minor]->hid;
+       struct hid_device *dev;
        __u8 *buf;
        int ret = 0;
 
+       if (!hidraw_table[minor])
+               return -ENODEV;
+
+       dev = hidraw_table[minor]->hid;
+
        if (!dev->hid_output_raw_report)
                return -ENODEV;