Re: [PATCH] [media] mxl111sf: Fix potential null pointer dereference

[Michael Ira Krufky]

On Sun, Aug 13, 2017 at 6:06 AM, Eugeniu Rosca  wrote:
> From: Eugeniu Rosca 
>
> 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 
> ---
>  drivers/media/usb/dvb-usb-v2/mxl111sf.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)


Reviewed-by:  Michael Ira Krufky 


Thank you for this, Eugeniu




> diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c 
> b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
> index b0d5904a4ea6..67953360fda5 100644
> --- 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);
> --
> 2.14.1
>

[PATCH] [media] mxl111sf: Fix potential null pointer dereference

[Eugeniu Rosca]

From: Eugeniu Rosca 

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 
---
 drivers/media/usb/dvb-usb-v2/mxl111sf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c 
b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index b0d5904a4ea6..67953360fda5 100644
--- 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);
-- 
2.14.1