[PATCH] igc: Do not use link uninitialized in igc_check_for_copper_link

[PATCH] igc: Do not use link uninitialized in igc_check_for_copper_link

[Nathan Chancellor]

Clang warns:

drivers/net/ethernet/intel/igc/igc_mac.c:374:6: warning: variable 'link'
is used uninitialized whenever 'if' condition is true
[-Wsometimes-uninitialized]
        if (!mac->get_link_status) {
            ^~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/intel/igc/igc_mac.c:424:33: note: uninitialized use
occurs here
        ret_val = igc_set_ltr_i225(hw, link);
                                       ^~~~
drivers/net/ethernet/intel/igc/igc_mac.c:374:2: note: remove the 'if' if
its condition is always false
        if (!mac->get_link_status) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/intel/igc/igc_mac.c:367:11: note: initialize the
variable 'link' to silence this warning
        bool link;
                 ^
                  = 0
1 warning generated.

It is not wrong, link is only uninitialized after this through
igc_phy_has_link. Presumably, if we skip the majority of this function
when get_link_status is false, we should skip calling igc_set_ltr_i225
as well. Just directly return 0 in this case, rather than bothering with
adding another label or initializing link in the if statement.

Fixes: 707abf069548 ("igc: Add initial LTR support")
Link: https://github.com/ClangBuiltLinux/linux/issues/1095
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 drivers/net/ethernet/intel/igc/igc_mac.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_mac.c b/drivers/net/ethernet/intel/igc/igc_mac.c
index b47e7b0a6398..26e3c56a4a8b 100644
--- a/drivers/net/ethernet/intel/igc/igc_mac.c
+++ b/drivers/net/ethernet/intel/igc/igc_mac.c
@@ -371,10 +371,8 @@ s32 igc_check_for_copper_link(struct igc_hw *hw)
 	 * get_link_status flag is set upon receiving a Link Status
 	 * Change or Rx Sequence Error interrupt.
 	 */
-	if (!mac->get_link_status) {
-		ret_val = 0;
-		goto out;
-	}
+	if (!mac->get_link_status)
+		return 0;
 
 	/* First we want to see if the MII Status Register reports
 	 * link.  If so, then we want to get the current speed/duplex

base-commit: ca0e494af5edb59002665bf12871e94b4163a257
-- 
2.28.0.rc0

Re: [Intel-wired-lan] [PATCH] igc: Do not use link uninitialized in igc_check_for_copper_link

[Neftin, Sasha]

On 7/16/2020 07:49, Nathan Chancellor wrote:
> Clang warns:
> 
Hello Nathan,
Thanks for tracking our code.Please, look at 
https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20200709073416.14126-1-sasha.neftin@intel.com/ 
- I hope this patch already address this Clang warns - please, let me know.
> drivers/net/ethernet/intel/igc/igc_mac.c:374:6: warning: variable 'link'
> is used uninitialized whenever 'if' condition is true
> [-Wsometimes-uninitialized]
>          if (!mac->get_link_status) {
>              ^~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/intel/igc/igc_mac.c:424:33: note: uninitialized use
> occurs here
>          ret_val = igc_set_ltr_i225(hw, link);
>                                         ^~~~
> drivers/net/ethernet/intel/igc/igc_mac.c:374:2: note: remove the 'if' if
> its condition is always false
>          if (!mac->get_link_status) {
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/intel/igc/igc_mac.c:367:11: note: initialize the
> variable 'link' to silence this warning
>          bool link;
>                   ^
>                    = 0
> 1 warning generated.
> 
> It is not wrong, link is only uninitialized after this through
> igc_phy_has_link. Presumably, if we skip the majority of this function
> when get_link_status is false, we should skip calling igc_set_ltr_i225
> as well. Just directly return 0 in this case, rather than bothering with
> adding another label or initializing link in the if statement.
> 
> Fixes: 707abf069548 ("igc: Add initial LTR support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1095
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>   drivers/net/ethernet/intel/igc/igc_mac.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_mac.c b/drivers/net/ethernet/intel/igc/igc_mac.c
> index b47e7b0a6398..26e3c56a4a8b 100644
> --- a/drivers/net/ethernet/intel/igc/igc_mac.c
> +++ b/drivers/net/ethernet/intel/igc/igc_mac.c
> @@ -371,10 +371,8 @@ s32 igc_check_for_copper_link(struct igc_hw *hw)
>   	 * get_link_status flag is set upon receiving a Link Status
>   	 * Change or Rx Sequence Error interrupt.
>   	 */
> -	if (!mac->get_link_status) {
> -		ret_val = 0;
> -		goto out;
> -	}
> +	if (!mac->get_link_status)
> +		return 0;
>   
>   	/* First we want to see if the MII Status Register reports
>   	 * link.  If so, then we want to get the current speed/duplex
> 
> base-commit: ca0e494af5edb59002665bf12871e94b4163a257
> 
Thanks,
Sasha

Re: [Intel-wired-lan] [PATCH] igc: Do not use link uninitialized in igc_check_for_copper_link

[Nathan Chancellor]

On Thu, Jul 16, 2020 at 07:29:03PM +0300, Neftin, Sasha wrote:
> On 7/16/2020 07:49, Nathan Chancellor wrote:
> > Clang warns:
> > 
> Hello Nathan,
> Thanks for tracking our code.Please, look at https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20200709073416.14126-1-sasha.neftin@intel.com/
> - I hope this patch already address this Clang warns - please, let me know.

I have not explicitly tested it but it seems obvious that it will. Let's
go with that.

Cheers,
Nathan

> > drivers/net/ethernet/intel/igc/igc_mac.c:374:6: warning: variable 'link'
> > is used uninitialized whenever 'if' condition is true
> > [-Wsometimes-uninitialized]
> >          if (!mac->get_link_status) {
> >              ^~~~~~~~~~~~~~~~~~~~~
> > drivers/net/ethernet/intel/igc/igc_mac.c:424:33: note: uninitialized use
> > occurs here
> >          ret_val = igc_set_ltr_i225(hw, link);
> >                                         ^~~~
> > drivers/net/ethernet/intel/igc/igc_mac.c:374:2: note: remove the 'if' if
> > its condition is always false
> >          if (!mac->get_link_status) {
> >          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/net/ethernet/intel/igc/igc_mac.c:367:11: note: initialize the
> > variable 'link' to silence this warning
> >          bool link;
> >                   ^
> >                    = 0
> > 1 warning generated.
> > 
> > It is not wrong, link is only uninitialized after this through
> > igc_phy_has_link. Presumably, if we skip the majority of this function
> > when get_link_status is false, we should skip calling igc_set_ltr_i225
> > as well. Just directly return 0 in this case, rather than bothering with
> > adding another label or initializing link in the if statement.
> > 
> > Fixes: 707abf069548 ("igc: Add initial LTR support")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1095
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> >   drivers/net/ethernet/intel/igc/igc_mac.c | 6 ++----
> >   1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/igc/igc_mac.c b/drivers/net/ethernet/intel/igc/igc_mac.c
> > index b47e7b0a6398..26e3c56a4a8b 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_mac.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_mac.c
> > @@ -371,10 +371,8 @@ s32 igc_check_for_copper_link(struct igc_hw *hw)
> >   	 * get_link_status flag is set upon receiving a Link Status
> >   	 * Change or Rx Sequence Error interrupt.
> >   	 */
> > -	if (!mac->get_link_status) {
> > -		ret_val = 0;
> > -		goto out;
> > -	}
> > +	if (!mac->get_link_status)
> > +		return 0;
> >   	/* First we want to see if the MII Status Register reports
> >   	 * link.  If so, then we want to get the current speed/duplex
> > 
> > base-commit: ca0e494af5edb59002665bf12871e94b4163a257
> > 
> Thanks,
> Sasha

Re: [Intel-wired-lan] [PATCH] igc: Do not use link uninitialized in igc_check_for_copper_link

[Neftin, Sasha]

On 7/17/2020 05:12, Nathan Chancellor wrote:
> On Thu, Jul 16, 2020 at 07:29:03PM +0300, Neftin, Sasha wrote:
>> On 7/16/2020 07:49, Nathan Chancellor wrote:
>>> Clang warns:
>>>
>> Hello Nathan,
>> Thanks for tracking our code.Please, look at https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20200709073416.14126-1-sasha.neftin@intel.com/
>> - I hope this patch already address this Clang warns - please, let me know.
> 
> I have not explicitly tested it but it seems obvious that it will. Let's
> go with that.
> 
Good Nathan, let's go with my 
https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20200709073416.14126-1-sasha.neftin@intel.com/ 
and let me know if warning still generated.
Thanks,
Sasha
> Cheers,
> Nathan
> 
>>> drivers/net/ethernet/intel/igc/igc_mac.c:374:6: warning: variable 'link'
>>> is used uninitialized whenever 'if' condition is true
>>> [-Wsometimes-uninitialized]
>>>           if (!mac->get_link_status) {
>>>               ^~~~~~~~~~~~~~~~~~~~~
>>> drivers/net/ethernet/intel/igc/igc_mac.c:424:33: note: uninitialized use
>>> occurs here
>>>           ret_val = igc_set_ltr_i225(hw, link);
>>>                                          ^~~~
>>> drivers/net/ethernet/intel/igc/igc_mac.c:374:2: note: remove the 'if' if
>>> its condition is always false
>>>           if (!mac->get_link_status) {
>>>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> drivers/net/ethernet/intel/igc/igc_mac.c:367:11: note: initialize the
>>> variable 'link' to silence this warning
>>>           bool link;
>>>                    ^
>>>                     = 0
>>> 1 warning generated.
>>>
>>> It is not wrong, link is only uninitialized after this through
>>> igc_phy_has_link. Presumably, if we skip the majority of this function
>>> when get_link_status is false, we should skip calling igc_set_ltr_i225
>>> as well. Just directly return 0 in this case, rather than bothering with
>>> adding another label or initializing link in the if statement.
>>>
>>> Fixes: 707abf069548 ("igc: Add initial LTR support")
>>> Link: https://github.com/ClangBuiltLinux/linux/issues/1095
>>> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
>>> ---
>>>    drivers/net/ethernet/intel/igc/igc_mac.c | 6 ++----
>>>    1 file changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/intel/igc/igc_mac.c b/drivers/net/ethernet/intel/igc/igc_mac.c
>>> index b47e7b0a6398..26e3c56a4a8b 100644
>>> --- a/drivers/net/ethernet/intel/igc/igc_mac.c
>>> +++ b/drivers/net/ethernet/intel/igc/igc_mac.c
>>> @@ -371,10 +371,8 @@ s32 igc_check_for_copper_link(struct igc_hw *hw)
>>>    	 * get_link_status flag is set upon receiving a Link Status
>>>    	 * Change or Rx Sequence Error interrupt.
>>>    	 */
>>> -	if (!mac->get_link_status) {
>>> -		ret_val = 0;
>>> -		goto out;
>>> -	}
>>> +	if (!mac->get_link_status)
>>> +		return 0;
>>>    	/* First we want to see if the MII Status Register reports
>>>    	 * link.  If so, then we want to get the current speed/duplex
>>>
>>> base-commit: ca0e494af5edb59002665bf12871e94b4163a257
>>>
>> Thanks,
>> Sasha