[Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Jiunn Chang]

Shifting signed 32-bit value by 31 bits is undefined.  Changing most
significant bit to unsigned.

Changes included in v2:
  - use subsystem specific subject lines
  - CC required mailing lists

Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
---
 include/uapi/linux/nl80211.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 6f09d1500960..fa7ebbc6ff27 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -5314,7 +5314,7 @@ enum nl80211_feature_flags {
 	NL80211_FEATURE_TDLS_CHANNEL_SWITCH		= 1 << 28,
 	NL80211_FEATURE_SCAN_RANDOM_MAC_ADDR		= 1 << 29,
 	NL80211_FEATURE_SCHED_SCAN_RANDOM_MAC_ADDR	= 1 << 30,
-	NL80211_FEATURE_ND_RANDOM_MAC_ADDR		= 1 << 31,
+	NL80211_FEATURE_ND_RANDOM_MAC_ADDR		= 1U << 31,
 };
 
 /**
-- 
2.22.0

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Shuah Khan]

On 6/26/19 9:25 PM, Jiunn Chang wrote:
> Shifting signed 32-bit value by 31 bits is undefined.  Changing most
> significant bit to unsigned.
> 
> Changes included in v2:
>    - use subsystem specific subject lines
>    - CC required mailing lists
> 
> Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
> ---

Move version change lines here. They don't belong in the commit log.

>   include/uapi/linux/nl80211.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
> index 6f09d1500960..fa7ebbc6ff27 100644
> --- a/include/uapi/linux/nl80211.h
> +++ b/include/uapi/linux/nl80211.h
> @@ -5314,7 +5314,7 @@ enum nl80211_feature_flags {
>   	NL80211_FEATURE_TDLS_CHANNEL_SWITCH		= 1 << 28,
>   	NL80211_FEATURE_SCAN_RANDOM_MAC_ADDR		= 1 << 29,
>   	NL80211_FEATURE_SCHED_SCAN_RANDOM_MAC_ADDR	= 1 << 30,
> -	NL80211_FEATURE_ND_RANDOM_MAC_ADDR		= 1 << 31,
> +	NL80211_FEATURE_ND_RANDOM_MAC_ADDR		= 1U << 31,
>   };
>   
>   /**
> 

thanks,
-- Shuah

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Johannes Berg]

On Wed, 2019-06-26 at 21:34 -0600, Shuah Khan wrote:
> On 6/26/19 9:25 PM, Jiunn Chang wrote:
> > Shifting signed 32-bit value by 31 bits is undefined.  Changing most
> > significant bit to unsigned.
> > 
> > Changes included in v2:
> >    - use subsystem specific subject lines
> >    - CC required mailing lists
> > 
> > Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
> > ---
> 
> Move version change lines here. They don't belong in the commit log.

FWIW, in many cases people (maintainers) now *do* want them in the
commit log. Here, they're just editorial, so agree, but if real
technical changes were made due to reviews, they can indeed be useful.

johannes

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Shuah Khan]

On 6/28/19 7:57 AM, Johannes Berg wrote:
> On Wed, 2019-06-26 at 21:34 -0600, Shuah Khan wrote:
>> On 6/26/19 9:25 PM, Jiunn Chang wrote:
>>> Shifting signed 32-bit value by 31 bits is undefined.  Changing most
>>> significant bit to unsigned.
>>>
>>> Changes included in v2:
>>>     - use subsystem specific subject lines
>>>     - CC required mailing lists
>>>
>>> Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
>>> ---
>>
>> Move version change lines here. They don't belong in the commit log.
> 
> FWIW, in many cases people (maintainers) now *do* want them in the
> commit log. Here, they're just editorial, so agree, but if real
> technical changes were made due to reviews, they can indeed be useful.
> 
> johannes
> 

I went looking in the git log. Looks like there are several commits with
"Changes since" included in the commit log. It still appears to be
maintainer preference. Probably from networking and networking related
areas - wireless being one of them. This trend is recent it appears in
any case.

There is a value to seeing changes as the work evolves. However, there
is the concern that how log should it be.

This example commit has history from RFC stage and no doubt very useful
since this is a new driver.

8ef988b914bd449458eb2174febb67b0f137b33c

If we make this more of a norm, we do want to make sure, we evolve
from informal nature of these "Changes since", to "Commit log" text.

thanks,
-- Shuah

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Johannes Berg]

Hi Shuah,

> I went looking in the git log. Looks like there are several commits with
> "Changes since" included in the commit log. It still appears to be
> maintainer preference. Probably from networking and networking related
> areas - wireless being one of them. This trend is recent it appears in
> any case.

Yeah. I was really just observing that I'd seen this, and some people (I
guess 'many' was an exaggeration) actively request it to be in the
commit log. I "grew up" with "changelog after ---" too ;-)

> There is a value to seeing changes as the work evolves. However, there
> is the concern that how log should it be.

That doesn't parse, what did you mean?

> This example commit has history from RFC stage and no doubt very useful
> since this is a new driver.
> 
> 8ef988b914bd449458eb2174febb67b0f137b33c
> 
> If we make this more of a norm, we do want to make sure, we evolve
> from informal nature of these "Changes since", to "Commit log" text.

Not sure it's really worth it, but I guess some recommendations could be
useful. If it is indeed to become the norm, and there aren't some people
who strongly feel it should *not* be included.

johannes

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Shuah Khan]

On 6/28/19 9:17 AM, Johannes Berg wrote:
> Hi Shuah,
> 
>> I went looking in the git log. Looks like there are several commits with
>> "Changes since" included in the commit log. It still appears to be
>> maintainer preference. Probably from networking and networking related
>> areas - wireless being one of them. This trend is recent it appears in
>> any case.
> 
> Yeah. I was really just observing that I'd seen this, and some people (I
> guess 'many' was an exaggeration) actively request it to be in the
> commit log. I "grew up" with "changelog after ---" too ;-)
> 
>> There is a value to seeing changes as the work evolves. However, there
>> is the concern that how log should it be.
> 
> That doesn't parse, what did you mean?

Say we are on version 16 of a patch series, when does the commit log
become too long to be useful?

> 
>> This example commit has history from RFC stage and no doubt very useful
>> since this is a new driver.
>>
>> 8ef988b914bd449458eb2174febb67b0f137b33c
>>

This commit has a very long commit log starting from RFC stage. It is
very informative.

>> If we make this more of a norm, we do want to make sure, we evolve
>> from informal nature of these "Changes since", to "Commit log" text.
> 
> Not sure it's really worth it, but I guess some recommendations could be
> useful. If it is indeed to become the norm, and there aren't some people
> who strongly feel it should *not* be included.
> 

Yeah. If it becomes a norm, we probably will have to set some limits how
long, and reads like part of the commit log as opposed to something
slapped on at the end.

thanks,
-- Shuah

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Jiunn Chang]

On Fri, Jun 28, 2019 at 03:57:05PM +0200, Johannes Berg wrote:
> On Wed, 2019-06-26 at 21:34 -0600, Shuah Khan wrote:
> > On 6/26/19 9:25 PM, Jiunn Chang wrote:
> > > Shifting signed 32-bit value by 31 bits is undefined.  Changing most
> > > significant bit to unsigned.
> > > 
> > > Changes included in v2:
> > >    - use subsystem specific subject lines
> > >    - CC required mailing lists
> > > 
> > > Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
> > > ---
> > 
> > Move version change lines here. They don't belong in the commit log.
> 
> FWIW, in many cases people (maintainers) now *do* want them in the
> commit log. Here, they're just editorial, so agree, but if real
> technical changes were made due to reviews, they can indeed be useful.
> 
> johannes
> 

Hello Johannes,

Would you like me to send v3 with the change log in the patch description?

THX,

Jiunn

Re: [Linux-kernel-mentees][PATCH v2] nl80211: Fix undefined behavior in bit shift

[Johannes Berg]

On Thu, 2019-07-04 at 13:34 -0500, Jiunn Chang wrote:
> Would you like me to send v3 with the change log in the patch description?
> 
No no, like I said, it's not very useful in this case anyway.

johannes

[Linux-kernel-mentees][PATCH v3] nl80211: Fix undefined behavior in bit shift

[Jiunn Chang]

Shifting signed 32-bit value by 31 bits is undefined.  Changing most
significant bit to unsigned.

Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
---
Changes included in v3:
  - remove change log from patch description

Changes included in v2:
  - use subsystem specific subject lines
  - CC required mailing lists

 include/uapi/linux/nl80211.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 6f09d1500960..fa7ebbc6ff27 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -5314,7 +5314,7 @@ enum nl80211_feature_flags {
 	NL80211_FEATURE_TDLS_CHANNEL_SWITCH		= 1 << 28,
 	NL80211_FEATURE_SCAN_RANDOM_MAC_ADDR		= 1 << 29,
 	NL80211_FEATURE_SCHED_SCAN_RANDOM_MAC_ADDR	= 1 << 30,
-	NL80211_FEATURE_ND_RANDOM_MAC_ADDR		= 1 << 31,
+	NL80211_FEATURE_ND_RANDOM_MAC_ADDR		= 1U << 31,
 };
 
 /**
-- 
2.22.0