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[PATCH 4.9 01/12] p54: memset(0) whole array

Started byGreg Kroah-Hartman <gregkh@linuxfoundation.org>
First post2017-08-31 17:50 +0200
Last post2017-09-03 17:10 +0200
Articles 5 — 3 participants

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  [PATCH 4.9 01/12] p54: memset(0) whole array Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-31 17:50 +0200
    Re: [PATCH 4.9 01/12] p54: memset(0) whole array Joe Perches <joe@perches.com> - 2017-08-31 18:50 +0200
      Re: [PATCH 4.9 01/12] p54: memset(0) whole array Joe Perches <joe@perches.com> - 2017-09-02 18:00 +0200
        Re: [PATCH 4.9 01/12] p54: memset(0) whole array Christian Lamparter <chunkeey@googlemail.com> - 2017-09-03 14:40 +0200
          Re: [PATCH 4.9 01/12] p54: memset(0) whole array Joe Perches <joe@perches.com> - 2017-09-03 17:10 +0200

#1724329 — [PATCH 4.9 01/12] p54: memset(0) whole array

FromGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Date2017-08-31 17:50 +0200
Subject[PATCH 4.9 01/12] p54: memset(0) whole array
Message-ID<ukzTc-7qZ-3@gated-at.bofh.it>
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Slaby <jslaby@suse.cz>

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@suse.cz>
Cc: Christian Lamparter <chunkeey@googlemail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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));

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#1724412

FromJoe Perches <joe@perches.com>
Date2017-08-31 18:50 +0200
Message-ID<ukAPg-81j-19@gated-at.bofh.it>
In reply to#1724329
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@suse.cz>
> 
> 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@suse.cz>
> Cc: Christian Lamparter <chunkeey@googlemail.com>
> Cc: Kalle Valo <kvalo@codeaurora.org>
> Acked-by: Christian Lamparter <chunkeey@googlemail.com>
> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> ---
>  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

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#1725530

FromJoe Perches <joe@perches.com>
Date2017-09-02 18:00 +0200
Message-ID<uliZY-4Mu-31@gated-at.bofh.it>
In reply to#1724412
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@suse.cz>
> > 
> > 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@suse.cz>
> > Cc: Christian Lamparter <chunkeey@googlemail.com>
> > Cc: Kalle Valo <kvalo@codeaurora.org>
> > Acked-by: Christian Lamparter <chunkeey@googlemail.com>
> > Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > 
> > ---
> >  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.

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#1725658

FromChristian Lamparter <chunkeey@googlemail.com>
Date2017-09-03 14:40 +0200
Message-ID<ulClY-8pn-19@gated-at.bofh.it>
In reply to#1725530
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@suse.cz>
> > > 
> > > 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@suse.cz>
> > > Cc: Christian Lamparter <chunkeey@googlemail.com>
> > > Cc: Kalle Valo <kvalo@codeaurora.org>
> > > Acked-by: Christian Lamparter <chunkeey@googlemail.com>
> > > Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > 
> > > ---
> > >  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>

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#1725701

FromJoe Perches <joe@perches.com>
Date2017-09-03 17:10 +0200
Message-ID<ulEH8-1wd-9@gated-at.bofh.it>
In reply to#1725658
On Sun, 2017-09-03 at 14:32 +0200, Christian Lamparter wrote:
> 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.
[]
> > > > +++ 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]:
[]
> yes: "curve_data" is a pointer.

Thank you.
My mistake, curve_data here is an array of structs.

> This means that chan->curve_data is 64 bytes in total.

I saw only:

drivers/net/wireless/intersil/p54/p54.h:        struct p54_cal_database *curve_data;

and did not notice

drivers/net/wireless/intersil/p54/lmac.h:       struct p54_pa_curve_data_sample curve_data[8];

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