HID: u2fzero: ignore incomplete packets without data

Since the actual_length calculation is performed unsigned, packets
shorter than 7 bytes (e.g. packets without data or otherwise truncated)
or non-received packets ("zero" bytes) can cause buffer overflow.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=214437
Fixes: 42337b9d4d958("HID: add driver for U2F Zero built-in LED and RNG")
Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-u2fzero.c b/drivers/hid/hid-u2fzero.c
index 95e0807..d70cd3d 100644 (file)
--- a/drivers/hid/hid-u2fzero.c
+++ b/drivers/hid/hid-u2fzero.c
@@ -198,7 +198,9 @@ static int u2fzero_rng_read(struct hwrng *rng, void *data,
        }
 
        ret = u2fzero_recv(dev, &req, &resp);
-       if (ret < 0)
+
+       /* ignore errors or packets without data */
+       if (ret < offsetof(struct u2f_hid_msg, init.data))
                return 0;
 
        /* only take the minimum amount of data it is safe to take */