[PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[kys]

From: Dexuan Cui <decui@microsoft.com>

In kvp_send_key(), we do need call process_ib_ipinfo() if
message->kvp_hdr.operation is KVP_OP_GET_IP_INFO, because it turns out
the userland hv_kvp_daemon needs the info of operation, adapter_id and
addr_family. With the incorrect fc62c3b1977d, the host can't get the
VM's IP via KVP.

And, fc62c3b1977d added a "break;", but actually forgot to initialize
the key_size/value in the case of KVP_OP_SET, so the default key_size of
0 is passed to the kvp daemon, and the pool files
/var/lib/hyperv/.kvp_pool_* can't be updated.

This patch effectively rolls back the previous fc62c3b1977d, and
correctly fixes the "this statement may fall through" warnings.

This patch is tested on WS 2012 R2 and 2016.

Fixes: fc62c3b1977d ("Drivers: hv: kvp: Fix two "this statement may fall through" warnings")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv_kvp.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index a7513a8a8e37..9fbb15c62c6c 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void *out_msg, int op)
 
 		out->body.kvp_ip_val.dhcp_enabled = in->kvp_ip_val.dhcp_enabled;
 
+		__attribute__ ((fallthrough));
+
+	case KVP_OP_GET_IP_INFO:
 		utf16s_to_utf8s((wchar_t *)in->kvp_ip_val.adapter_id,
 				MAX_ADAPTER_ID_SIZE,
 				UTF16_LITTLE_ENDIAN,
@@ -405,7 +408,11 @@ kvp_send_key(struct work_struct *dummy)
 		process_ib_ipinfo(in_msg, message, KVP_OP_SET_IP_INFO);
 		break;
 	case KVP_OP_GET_IP_INFO:
-		/* We only need to pass on message->kvp_hdr.operation.  */
+		/*
+		 * We only need to pass on the info of operation, adapter_id
+		 * and addr_family to the userland kvp daemon.
+		 */
+		process_ib_ipinfo(in_msg, message, KVP_OP_GET_IP_INFO);
 		break;
 	case KVP_OP_SET:
 		switch (in_msg->body.kvp_set.data.value_type) {
@@ -446,9 +453,9 @@ kvp_send_key(struct work_struct *dummy)
 
 		}
 
-		break;
-
-	case KVP_OP_GET:
+		/*
+		 * The key is always a string - utf16 encoding.
+		 */
 		message->body.kvp_set.data.key_size =
 			utf16s_to_utf8s(
 			(wchar_t *)in_msg->body.kvp_set.data.key,
@@ -456,6 +463,17 @@ kvp_send_key(struct work_struct *dummy)
 			UTF16_LITTLE_ENDIAN,
 			message->body.kvp_set.data.key,
 			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
+
+		break;
+
+	case KVP_OP_GET:
+		message->body.kvp_get.data.key_size =
+			utf16s_to_utf8s(
+			(wchar_t *)in_msg->body.kvp_get.data.key,
+			in_msg->body.kvp_get.data.key_size,
+			UTF16_LITTLE_ENDIAN,
+			message->body.kvp_get.data.key,
+			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
 		break;
 
 	case KVP_OP_DELETE:
-- 
2.18.0

Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Greg KH]

On Wed, Oct 17, 2018 at 03:14:04AM +0000, kys@linuxonhyperv.com wrote:
> From: Dexuan Cui <decui@microsoft.com>
> 
> In kvp_send_key(), we do need call process_ib_ipinfo() if
> message->kvp_hdr.operation is KVP_OP_GET_IP_INFO, because it turns out
> the userland hv_kvp_daemon needs the info of operation, adapter_id and
> addr_family. With the incorrect fc62c3b1977d, the host can't get the
> VM's IP via KVP.
> 
> And, fc62c3b1977d added a "break;", but actually forgot to initialize
> the key_size/value in the case of KVP_OP_SET, so the default key_size of
> 0 is passed to the kvp daemon, and the pool files
> /var/lib/hyperv/.kvp_pool_* can't be updated.
> 
> This patch effectively rolls back the previous fc62c3b1977d, and
> correctly fixes the "this statement may fall through" warnings.
> 
> This patch is tested on WS 2012 R2 and 2016.
> 
> Fixes: fc62c3b1977d ("Drivers: hv: kvp: Fix two "this statement may fall through" warnings")
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: <Stable@vger.kernel.org>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  drivers/hv/hv_kvp.c | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index a7513a8a8e37..9fbb15c62c6c 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
> @@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void *out_msg, int op)
>  
>  		out->body.kvp_ip_val.dhcp_enabled = in->kvp_ip_val.dhcp_enabled;
>  
> +		__attribute__ ((fallthrough));

The comment should be sufficient for this, right?  I haven't seen many
uses of this attribute before, how common is it?


> +
> +	case KVP_OP_GET_IP_INFO:
>  		utf16s_to_utf8s((wchar_t *)in->kvp_ip_val.adapter_id,
>  				MAX_ADAPTER_ID_SIZE,
>  				UTF16_LITTLE_ENDIAN,
> @@ -405,7 +408,11 @@ kvp_send_key(struct work_struct *dummy)
>  		process_ib_ipinfo(in_msg, message, KVP_OP_SET_IP_INFO);
>  		break;
>  	case KVP_OP_GET_IP_INFO:
> -		/* We only need to pass on message->kvp_hdr.operation.  */
> +		/*
> +		 * We only need to pass on the info of operation, adapter_id
> +		 * and addr_family to the userland kvp daemon.
> +		 */
> +		process_ib_ipinfo(in_msg, message, KVP_OP_GET_IP_INFO);
>  		break;
>  	case KVP_OP_SET:
>  		switch (in_msg->body.kvp_set.data.value_type) {
> @@ -446,9 +453,9 @@ kvp_send_key(struct work_struct *dummy)
>  
>  		}
>  
> -		break;
> -
> -	case KVP_OP_GET:
> +		/*
> +		 * The key is always a string - utf16 encoding.
> +		 */
>  		message->body.kvp_set.data.key_size =
>  			utf16s_to_utf8s(
>  			(wchar_t *)in_msg->body.kvp_set.data.key,
> @@ -456,6 +463,17 @@ kvp_send_key(struct work_struct *dummy)
>  			UTF16_LITTLE_ENDIAN,
>  			message->body.kvp_set.data.key,
>  			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
> +
> +		break;
> +
> +	case KVP_OP_GET:
> +		message->body.kvp_get.data.key_size =
> +			utf16s_to_utf8s(
> +			(wchar_t *)in_msg->body.kvp_get.data.key,
> +			in_msg->body.kvp_get.data.key_size,
> +			UTF16_LITTLE_ENDIAN,
> +			message->body.kvp_get.data.key,
> +			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;

Worst indentation ever :(

Yeah, I know it follows the others above it, but you should reconsider
it in the future...

thanks,

greg k-h

RE: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[KY Srinivasan]

> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Tuesday, October 16, 2018 10:07 PM
> To: KY Srinivasan <kys@microsoft.com>
> Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org;
> olaf@aepfle.de; apw@canonical.com; jasowang@redhat.com; Stephen
> Hemminger <sthemmin@microsoft.com>; Michael Kelley (EOSG)
> <Michael.H.Kelley@microsoft.com>; vkuznets <vkuznets@redhat.com>;
> Haiyang Zhang <haiyangz@microsoft.com>; Stable@vger.kernel.org
> Subject: Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by
> incorrect clean-up
> 
> On Wed, Oct 17, 2018 at 03:14:04AM +0000, kys@linuxonhyperv.com wrote:
> > From: Dexuan Cui <decui@microsoft.com>
> >
> > In kvp_send_key(), we do need call process_ib_ipinfo() if
> > message->kvp_hdr.operation is KVP_OP_GET_IP_INFO, because it turns
> out
> > the userland hv_kvp_daemon needs the info of operation, adapter_id and
> > addr_family. With the incorrect fc62c3b1977d, the host can't get the
> > VM's IP via KVP.
> >
> > And, fc62c3b1977d added a "break;", but actually forgot to initialize
> > the key_size/value in the case of KVP_OP_SET, so the default key_size of
> > 0 is passed to the kvp daemon, and the pool files
> > /var/lib/hyperv/.kvp_pool_* can't be updated.
> >
> > This patch effectively rolls back the previous fc62c3b1977d, and
> > correctly fixes the "this statement may fall through" warnings.
> >
> > This patch is tested on WS 2012 R2 and 2016.
> >
> > Fixes: fc62c3b1977d ("Drivers: hv: kvp: Fix two "this statement may fall
> through" warnings")
> > Signed-off-by: Dexuan Cui <decui@microsoft.com>
> > Cc: K. Y. Srinivasan <kys@microsoft.com>
> > Cc: Haiyang Zhang <haiyangz@microsoft.com>
> > Cc: Stephen Hemminger <sthemmin@microsoft.com>
> > Cc: <Stable@vger.kernel.org>
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> >  drivers/hv/hv_kvp.c | 26 ++++++++++++++++++++++----
> >  1 file changed, 22 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> > index a7513a8a8e37..9fbb15c62c6c 100644
> > --- a/drivers/hv/hv_kvp.c
> > +++ b/drivers/hv/hv_kvp.c
> > @@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void
> *out_msg, int op)
> >
> >  		out->body.kvp_ip_val.dhcp_enabled = in-
> >kvp_ip_val.dhcp_enabled;
> >
> > +		__attribute__ ((fallthrough));
> 
> The comment should be sufficient for this, right?  I haven't seen many
> uses of this attribute before, how common is it?

Yes; a common should be sufficient.
> 
> 
> > +
> > +	case KVP_OP_GET_IP_INFO:
> >  		utf16s_to_utf8s((wchar_t *)in->kvp_ip_val.adapter_id,
> >  				MAX_ADAPTER_ID_SIZE,
> >  				UTF16_LITTLE_ENDIAN,
> > @@ -405,7 +408,11 @@ kvp_send_key(struct work_struct *dummy)
> >  		process_ib_ipinfo(in_msg, message, KVP_OP_SET_IP_INFO);
> >  		break;
> >  	case KVP_OP_GET_IP_INFO:
> > -		/* We only need to pass on message->kvp_hdr.operation.
> */
> > +		/*
> > +		 * We only need to pass on the info of operation, adapter_id
> > +		 * and addr_family to the userland kvp daemon.
> > +		 */
> > +		process_ib_ipinfo(in_msg, message,
> KVP_OP_GET_IP_INFO);
> >  		break;
> >  	case KVP_OP_SET:
> >  		switch (in_msg->body.kvp_set.data.value_type) {
> > @@ -446,9 +453,9 @@ kvp_send_key(struct work_struct *dummy)
> >
> >  		}
> >
> > -		break;
> > -
> > -	case KVP_OP_GET:
> > +		/*
> > +		 * The key is always a string - utf16 encoding.
> > +		 */
> >  		message->body.kvp_set.data.key_size =
> >  			utf16s_to_utf8s(
> >  			(wchar_t *)in_msg->body.kvp_set.data.key,
> > @@ -456,6 +463,17 @@ kvp_send_key(struct work_struct *dummy)
> >  			UTF16_LITTLE_ENDIAN,
> >  			message->body.kvp_set.data.key,
> >  			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
> > +
> > +		break;
> > +
> > +	case KVP_OP_GET:
> > +		message->body.kvp_get.data.key_size =
> > +			utf16s_to_utf8s(
> > +			(wchar_t *)in_msg->body.kvp_get.data.key,
> > +			in_msg->body.kvp_get.data.key_size,
> > +			UTF16_LITTLE_ENDIAN,
> > +			message->body.kvp_get.data.key,
> > +			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
> 
> Worst indentation ever :(
> 
> Yeah, I know it follows the others above it, but you should reconsider
> it in the future...
> 
> thanks,
> 
> greg k-h

RE: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Dexuan Cui]

> From: devel <driverdev-devel-bounces@linuxdriverproject.org> On Behalf Of
> KY Srinivasan
> Sent: Tuesday, October 16, 2018 23:02
> > > --- a/drivers/hv/hv_kvp.c
> > > +++ b/drivers/hv/hv_kvp.c
> > > @@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void
> > *out_msg, int op)
> > >
> > >  		out->body.kvp_ip_val.dhcp_enabled = in-
> > >kvp_ip_val.dhcp_enabled;
> > >
> > > +		__attribute__ ((fallthrough));
> >
> > The comment should be sufficient for this, right?  I haven't seen many
> > uses of this attribute before, how common is it?
> 
> Yes; a common should be sufficient.

You all are right. 
Right now, I realized the gcc warning can also be suppressed by a simple line
of comment:

/* fallthrough */

It looks gcc treats this comment specially. 

If I add something more in the comment, like
/* add fallthrough */
, the warning can not be suppressed. :-)

I'll do a new version for KY.

Thank you all!

-- Dexuan

Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Dan Carpenter]

On Wed, Oct 17, 2018 at 07:07:05AM +0200, Greg KH wrote:
> On Wed, Oct 17, 2018 at 03:14:04AM +0000, kys@linuxonhyperv.com wrote:
> > From: Dexuan Cui <decui@microsoft.com>
> > 
> > In kvp_send_key(), we do need call process_ib_ipinfo() if
> > message->kvp_hdr.operation is KVP_OP_GET_IP_INFO, because it turns out
> > the userland hv_kvp_daemon needs the info of operation, adapter_id and
> > addr_family. With the incorrect fc62c3b1977d, the host can't get the
> > VM's IP via KVP.
> > 
> > And, fc62c3b1977d added a "break;", but actually forgot to initialize
> > the key_size/value in the case of KVP_OP_SET, so the default key_size of
> > 0 is passed to the kvp daemon, and the pool files
> > /var/lib/hyperv/.kvp_pool_* can't be updated.
> > 
> > This patch effectively rolls back the previous fc62c3b1977d, and
> > correctly fixes the "this statement may fall through" warnings.
> > 
> > This patch is tested on WS 2012 R2 and 2016.
> > 
> > Fixes: fc62c3b1977d ("Drivers: hv: kvp: Fix two "this statement may fall through" warnings")
> > Signed-off-by: Dexuan Cui <decui@microsoft.com>
> > Cc: K. Y. Srinivasan <kys@microsoft.com>
> > Cc: Haiyang Zhang <haiyangz@microsoft.com>
> > Cc: Stephen Hemminger <sthemmin@microsoft.com>
> > Cc: <Stable@vger.kernel.org>
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> >  drivers/hv/hv_kvp.c | 26 ++++++++++++++++++++++----
> >  1 file changed, 22 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> > index a7513a8a8e37..9fbb15c62c6c 100644
> > --- a/drivers/hv/hv_kvp.c
> > +++ b/drivers/hv/hv_kvp.c
> > @@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void *out_msg, int op)
> >  
> >  		out->body.kvp_ip_val.dhcp_enabled = in->kvp_ip_val.dhcp_enabled;
> >  
> > +		__attribute__ ((fallthrough));
> 
> The comment should be sufficient for this, right?  I haven't seen many
> uses of this attribute before, how common is it?
>

It's not common at all.  It should be wrapped in a macro and put into
compiler.h.

But I hope it does become adopted.  It's better than randomly grepping
for non-standard comments.

regards,
dan carpenter

Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Miguel Ojeda]

+On Wed, Oct 17, 2018 at 8:25 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> It's not common at all.  It should be wrapped in a macro and put into
> compiler.h.
>
> But I hope it does become adopted.  It's better than randomly grepping
> for non-standard comments.

Using an attribute is indeed better whenever possible. In C++17 it is
an standard attribute and there have been proposals to include some of
them for C as well since 2016 at least, e.g. the latest for
fallthrough at:

  http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2268.pdf

I have taken a quick look into supporting it (typing it here to save
it on the mailing list :-), and we have:

  * gcc >= 7.1 supports -Wimplicit-fallthrough with
__attribute__((fallthrough)), the comment syntax and the C++
[[fallthrough]] syntax.
  * gcc < 7.1 complains about empty declarations (it does not know
about attributes for null statements) and also
-Wdeclaration-after-statement.
  * clang 7 supports -Wimplicit-fallthrough (not enabled in
-Wall/extra/pedantic like gcc, though) but *only* in C++ mode and with
the C++ syntax [[fallthrough]]. In other words, in C mode, no syntax
works and no diagnostics are emitted. It complains about
Wmissing-declarations. [IMO they should allow the __attribute__ syntax
for fallthrough (and enable it on C mode) to be compatible with gcc.
Maybe they are simply waiting for the C2x attributes... :-)]
  * icc 19 does not know about -Wimplicit-fallthrough at all (but
seems to allow [[fallthrough]] on C++17 mode to comply with the
standard).

Therefore, the only improvement we could do right now is starting to
use the attribute for gcc > 7.1, and a comment for everybody else.
However, even if that was worth the trouble of changing the 2500+
instances of fall through markings that we have, comments are replaced
before the preprocessor stage, so we would need some (probably
non-portable) macro magic.

So, I would say, let's revisit this again in a few years. Possibly,
when we move the minimum version to gcc 7.1, clang and icc may both
support the fallthrough warning in C mode; so that we can always use
the __attribute__((fallthrough)) unconditionally under a __fallthrough
#define.

Cheers,
Miguel

Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Dan Carpenter]

On Sat, Oct 20, 2018 at 04:42:07PM +0200, Miguel Ojeda wrote:
> +On Wed, Oct 17, 2018 at 8:25 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > It's not common at all.  It should be wrapped in a macro and put into
> > compiler.h.
> >
> > But I hope it does become adopted.  It's better than randomly grepping
> > for non-standard comments.
> 
> Using an attribute is indeed better whenever possible. In C++17 it is
> an standard attribute and there have been proposals to include some of
> them for C as well since 2016 at least, e.g. the latest for
> fallthrough at:
> 
>   http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2268.pdf
> 
> I have taken a quick look into supporting it (typing it here to save
> it on the mailing list :-), and we have:
> 
>   * gcc >= 7.1 supports -Wimplicit-fallthrough with
> __attribute__((fallthrough)), the comment syntax and the C++
> [[fallthrough]] syntax.
>   * gcc < 7.1 complains about empty declarations (it does not know
> about attributes for null statements) and also
> -Wdeclaration-after-statement.

I'm not sure I understand about empty decalarations.  The idea is that
we would do:

	case 3:
		frob();
		__fall_through();
	case 4:
		frob();

#if GCC > 7.1
#define __fall_through() __attribute__((fallthrough))
#else
#define __fall_through()
#endif

So long as GCC and static analysis tools understand about the attribute
that's enought to catch the bugs.  No one cares what clang and icc do.
We would just disable the fall through warnings on those until they are
updated to support the fallthrough attribute.

We wouldn't update all the fall through comments until later, but going
forward people could use the __fall_through() macro if they want.

regards,
dan carpenter

Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Miguel Ojeda]

Hi Dan,

On Sat, Oct 20, 2018 at 9:22 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> On Sat, Oct 20, 2018 at 04:42:07PM +0200, Miguel Ojeda wrote:
> > Using an attribute is indeed better whenever possible. In C++17 it is
> > an standard attribute and there have been proposals to include some of
> > them for C as well since 2016 at least, e.g. the latest for
> > fallthrough at:
> >
> >   http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2268.pdf
> >
> > I have taken a quick look into supporting it (typing it here to save
> > it on the mailing list :-), and we have:
> >
> >   * gcc >= 7.1 supports -Wimplicit-fallthrough with
> > __attribute__((fallthrough)), the comment syntax and the C++
> > [[fallthrough]] syntax.
> >   * gcc < 7.1 complains about empty declarations (it does not know
> > about attributes for null statements) and also
> > -Wdeclaration-after-statement.
>
> I'm not sure I understand about empty decalarations.  The idea is that
> we would do:

That paragraph tried to explain that gcc < 7.1 did not know about
__attribute__((fallthrough)); i.e. that everything was introduced in
gcc 7.1.

Anyway, the conclusion was a neuron misfiring of mine -- in my mind I
was thinking clang supported the comment syntax (when I clearly wrote
that it didn't). Never mind --- thanks for pointing it out!

>
>         case 3:
>                 frob();
>                 __fall_through();
>         case 4:
>                 frob();
>
> #if GCC > 7.1
> #define __fall_through() __attribute__((fallthrough))
> #else
> #define __fall_through()
> #endif

Yes, of course, that is what we do for other attributes -- actually in
-next we have pending a better way for checking, using
__has_attribute:

  #if __has_attribute(fallthrough)
  #define __fallthrough __attribute__((fallthrough))
  #else
  #define __fallthrough
  #endif

>
> So long as GCC and static analysis tools understand about the attribute
> that's enought to catch the bugs. No one cares what clang and icc do.

Not so sure about that -- there are quite some people looking forward
to building Linux with clang, even if only to have another compiler to
check for warnings and to use the clang/llvm-related tools (and to
write new ones).

> We would just disable the fall through warnings on those until they are
> updated to support the fallthrough attribute.

You mean if they start supporting the warning but not the attribute? I
don't think that would be likely (i.e. if clang enables the warning on
C mode, they will have to introduce a way to suppress it; which should
be the attribute (at least), since they typically like to be
compatible with gcc and since they already support it in C++ >= 11),
but everything is possible.

>
> We wouldn't update all the fall through comments until later, but going
> forward people could use the __fall_through() macro if they want.

Agreed. I will introduce it in the compiler-attributes tree -- should
be there for -rc1 if no one complains. CC'ing all of you in the patch.

Cheers,
Miguel

RE: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

[Dexuan Cui]

> From: devel <driverdev-devel-bounces@linuxdriverproject.org> On Behalf Of
> Greg KH
> Sent: Tuesday, October 16, 2018 22:07
> > ...
> > +	case KVP_OP_GET:
> > +		message->body.kvp_get.data.key_size =
> > +			utf16s_to_utf8s(
> > +			(wchar_t *)in_msg->body.kvp_get.data.key,
> > +			in_msg->body.kvp_get.data.key_size,
> > +			UTF16_LITTLE_ENDIAN,
> > +			message->body.kvp_get.data.key,
> > +			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
> 
> Worst indentation ever :(
> 
> Yeah, I know it follows the others above it, but you should reconsider
> it in the future...
> greg k-h

Agreed. We should consider improving this in future.

-- Dexuan

[PATCH 4/5] Drivers: hv: kvp: Use %u to print U32

[kys]

From: Dexuan Cui <decui@microsoft.com>

I didn't find a real issue. Let's just make it consistent with the
next "case REG_U64:" where %llu is used.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv_kvp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index 9fbb15c62c6c..3b8590ff94ba 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -437,7 +437,7 @@ kvp_send_key(struct work_struct *dummy)
 			val32 = in_msg->body.kvp_set.data.value_u32;
 			message->body.kvp_set.data.value_size =
 				sprintf(message->body.kvp_set.data.value,
-					"%d", val32) + 1;
+					"%u", val32) + 1;
 			break;
 
 		case REG_U64:
-- 
2.18.0

Re: [PATCH 4/5] Drivers: hv: kvp: Use %u to print U32

[Greg KH]

On Wed, Oct 17, 2018 at 03:14:05AM +0000, kys@linuxonhyperv.com wrote:
> From: Dexuan Cui <decui@microsoft.com>
> 
> I didn't find a real issue. Let's just make it consistent with the
> next "case REG_U64:" where %llu is used.
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: <Stable@vger.kernel.org>

Why is this a stable patch?

confused,

greg k-h

RE: [PATCH 4/5] Drivers: hv: kvp: Use %u to print U32

[KY Srinivasan]

> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Tuesday, October 16, 2018 10:04 PM
> To: KY Srinivasan <kys@microsoft.com>
> Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org;
> olaf@aepfle.de; apw@canonical.com; jasowang@redhat.com; Stephen
> Hemminger <sthemmin@microsoft.com>; Michael Kelley (EOSG)
> <Michael.H.Kelley@microsoft.com>; vkuznets <vkuznets@redhat.com>;
> Haiyang Zhang <haiyangz@microsoft.com>; Stable@vger.kernel.org
> Subject: Re: [PATCH 4/5] Drivers: hv: kvp: Use %u to print U32
> 
> On Wed, Oct 17, 2018 at 03:14:05AM +0000, kys@linuxonhyperv.com wrote:
> > From: Dexuan Cui <decui@microsoft.com>
> >
> > I didn't find a real issue. Let's just make it consistent with the
> > next "case REG_U64:" where %llu is used.
> >
> > Signed-off-by: Dexuan Cui <decui@microsoft.com>
> > Cc: K. Y. Srinivasan <kys@microsoft.com>
> > Cc: Haiyang Zhang <haiyangz@microsoft.com>
> > Cc: Stephen Hemminger <sthemmin@microsoft.com>
> > Cc: <Stable@vger.kernel.org>
> 
> Why is this a stable patch?

My mistake; I will resend.

K. Y
> 
> confused,
> 
> greg k-h

Re: [PATCH 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1

[Greg KH]

On Wed, Oct 17, 2018 at 03:14:06AM +0000, kys@linuxonhyperv.com wrote:
> From: Dexuan Cui <decui@microsoft.com>
> 
> The patch fixes:
> 
> hv_kvp_daemon.c: In function 'kvp_set_ip_info':
> hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes
> into a destination of size 4096
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: <Stable@vger.kernel.org>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  tools/hv/hv_kvp_daemon.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c
> index bbb2a8ef367c..b7c2cf7eaba5 100644
> --- a/tools/hv/hv_kvp_daemon.c
> +++ b/tools/hv/hv_kvp_daemon.c
> @@ -1176,7 +1176,7 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val)
>  	int error = 0;
>  	char if_file[PATH_MAX];
>  	FILE *file;
> -	char cmd[PATH_MAX];
> +	char cmd[PATH_MAX * 2];

Overkill?

RE: [PATCH 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1

[Dexuan Cui]

> From: devel <driverdev-devel-bounces@linuxdriverproject.org> On Behalf Of
> Greg KH
> Sent: Tuesday, October 16, 2018 22:07
> 
> On Wed, Oct 17, 2018 at 03:14:06AM +0000, kys@linuxonhyperv.com wrote:
> > From: Dexuan Cui <decui@microsoft.com>
> >
> > The patch fixes:
> >
> > hv_kvp_daemon.c: In function 'kvp_set_ip_info':
> > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes
> > into a destination of size 4096
> > ...
> > --- a/tools/hv/hv_kvp_daemon.c
> > +++ b/tools/hv/hv_kvp_daemon.c
> > @@ -1176,7 +1176,7 @@ static int kvp_set_ip_info(char *if_name, struct
> hv_kvp_ipaddr_value *new_val)
> >  	int error = 0;
> >  	char if_file[PATH_MAX];
> >  	FILE *file;
> > -	char cmd[PATH_MAX];
> > +	char cmd[PATH_MAX * 2];
> 
> Overkill?

Well, I found the -Wformat-truncation warning can be suppressed by checking
the return value of snprintf, so I'm going to do a new patch for KY to resend like this:

@@ -1178,6 +1178,7 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val)
        FILE *file;
        char cmd[PATH_MAX];
        char *mac_addr;
+       int str_len;

        /*
         * Set the configuration for the specified interface with
@@ -1301,8 +1302,19 @@ static int kvp_set_ip_info(char *if_name, struct hv_kvp_ipaddr_value *new_val)
         * invoke the external script to do its magic.
         */

-       snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s",
-                "hv_set_ifconfig", if_file);
+       str_len = snprintf(cmd, sizeof(cmd), KVP_SCRIPTS_PATH "%s %s",
+                    "hv_set_ifconfig", if_file);
+
+       /*
+        * This is a little overcautious, but it's necessary to suppress some
+        * false warnings from gcc 8.0.1.
+        */
+       if (str_len <= 0 || (unsigned int)str_len >= sizeof(cmd)) {
+               syslog(LOG_ERR, "Cmd '%s' (len=%d) may be too long",
+                      cmd, str_len);
+               return HV_E_FAIL;
+       }


Thanks,
-- Dexuan