[PATCH 5.10 81/93] HID: u2fzero: ignore incomplete packets without data

Greg Kroah-Hartman
2021-10-04T13:25:57Z

From: Andrej Shadura <andrew.shadura@collabora.co.uk>

commit 22d65765f211cc83186fd8b87521159f354c0da9 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/hid/hid-u2fzero.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/hid/hid-u2fzero.c
+++ b/drivers/hid/hid-u2fzero.c
@@ -198,7 +198,9 @@ static int u2fzero_rng_read(struct hwrng
}

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 */