On Saturday, September 2, 2017 8:51:01 AM CEST Joe Perches wrote: > On Thu, 2017-08-31 at 09:40 -0700, Joe Perches wrote: > > On Thu, 2017-08-31 at 17:44 +0200, Greg Kroah-Hartman wrote: > > > 4.9-stable review patch. If anyone has any objections, please let me know. > > > > > > ------------------ > > > > > > From: Jiri Slaby <jslaby@xxxxxxx> > > > > > > commit 6f17581788206444cbbcdbc107498f85e9765e3d upstream. > > > > > > gcc 7 complains: > > > drivers/net/wireless/intersil/p54/fwio.c: In function 'p54_scan': > > > drivers/net/wireless/intersil/p54/fwio.c:491:4: warning: 'memset' used with length equal to number of elements without multiplication by element size [-Wmemset-elt-size] > > > > > > Fix that by passing the correct size to memset. > > > > > > Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> > > > Cc: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx> > > > Cc: Kalle Valo <kvalo@xxxxxxxxxxxxxx> > > > Acked-by: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx> > > > Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > > > > > --- > > > drivers/net/wireless/intersil/p54/fwio.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > --- a/drivers/net/wireless/intersil/p54/fwio.c > > > +++ b/drivers/net/wireless/intersil/p54/fwio.c > > > @@ -488,7 +488,7 @@ int p54_scan(struct p54_common *priv, u1 > > > > > > entry += sizeof(__le16); > > > chan->pa_points_per_curve = 8; > > > - memset(chan->curve_data, 0, sizeof(*chan->curve_data)); > > > + memset(chan->curve_data, 0, sizeof(chan->curve_data)); > > > memcpy(chan->curve_data, entry, > > > sizeof(struct p54_pa_curve_data_sample) * > > > min((u8)8, curve_data->points_per_channel)); > > > > > > > Why is this change correct? > > > > curve_data is a pointer. > > > > This now clears the sizeof a pointer and not > > the sizeof struct p54_cal_database > > So what happens here? > This change seems clearly incorrect. > For all stable versions. hm? Please, just look again at [0]: | struct p54_scan_body *chan = &body->normal; | struct pda_pa_curve_data *curve_data = | (void *) priv->curve_data->data; | | entry += sizeof(__le16); | chan->pa_points_per_curve = 8; | memset(chan->curve_data, 0, sizeof(chan->curve_data)); | memcpy(chan->curve_data, entry, | sizeof(struct p54_pa_curve_data_sample) * | min((u8)8, curve_data->points_per_channel)); yes: "curve_data" is a pointer. But memset and memcpy are using "chan->curve_data". chan is a pointer to a p54_scan_body struct. The structure is defined in lmac.h: |struct p54_pa_curve_data_sample { | u8 rf_power; | u8 pa_detector; | u8 data_barker; | u8 data_bpsk; | u8 data_qpsk; | u8 data_16qam; | u8 data_64qam; | u8 padding; |} __packed; | |struct p54_scan_body { | u8 pa_points_per_curve; | u8 val_barker; | u8 val_bpsk; | u8 val_qpsk; | u8 val_16qam; | u8 val_64qam; | struct p54_pa_curve_data_sample curve_data[8]; | u8 dup_bpsk; | u8 dup_qpsk; | u8 dup_16qam; | u8 dup_64qam; |} __packed; p54_scan_body's curve_data is an array of eight p54_pa_curve_data_sample, each with eight u8. This means that chan->curve_data is 64 bytes in total. If you are not convinced yet, please add: BUILD_BUG_ON(sizeof(chan->curve_data) != 64); next to the memset and compile the driver. If this was all wrong, this would cause a build error, right? Regards, Christian [0] <http://elixir.free-electrons.com/linux/v4.13-rc7/source/drivers/net/wireless/intersil/p54/fwio.c#L485> [1] <http://elixir.free-electrons.com/linux/v4.13-rc7/source/drivers/net/wireless/intersil/p54/lmac.h#L351>