media: mxl111sf: Fix potential null pointer dereference

Reviewing the delta between cppcheck output of v4.9.39 and v4.9.40
stable updates, I stumbled on the new warning:

mxl111sf.c:80: (warning) Possible null pointer dereference: rbuf

Since copying state->rcvbuf into rbuf is not needed in the 'write-only'
scenario (i.e. calling mxl111sf_ctrl_msg() from mxl111sf_i2c_send_data()
or from mxl111sf_write_reg()), bypass memcpy() in this case.

Fixes: d90b336f3f65 ("[media] mxl111sf: Fix driver to use heap allocate buffers for USB messages")
Signed-off-by: Eugeniu Rosca <[email protected]>
Reviewed-by: Michael Ira Krufky <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index b0d5904a4ea662c29a9379d5d86b29575cbb6ec8..67953360fda586db9c1e9d904fc87d48f00df45f 100644 (file)
--- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
+++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
@@ -77,7 +77,9 @@ int mxl111sf_ctrl_msg(struct mxl111sf_state *state,
                dvb_usbv2_generic_rw(d, state->sndbuf, 1+wlen, state->rcvbuf,
                                     rlen);
 
-       memcpy(rbuf, state->rcvbuf, rlen);
+       if (rbuf)
+               memcpy(rbuf, state->rcvbuf, rlen);
+
        mutex_unlock(&state->msg_lock);
 
        mxl_fail(ret);