[PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[Nathan Chancellor]

Clang warns (trimmed for brevity):

drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3073:7: warning:
variable 'link' is used uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]
                if (val & MVPP22_XLG_STATUS_LINK_UP)
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3075:31: note:
uninitialized use occurs here
                mvpp2_isr_handle_link(port, link);
                                            ^~~~
...
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3090:8: warning:
variable 'link' is used uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]
                        if (val & MVPP2_GMAC_STATUS0_LINK_UP)
                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3092:32: note:
uninitialized use occurs here
                        mvpp2_isr_handle_link(port, link);
                                                    ^~~~

Initialize link to false like it was before the refactoring that
happened around link status so that a valid valid is always passed into
mvpp2_isr_handle_link.

Fixes: 36cfd3a6e52b ("net: mvpp2: restructure "link status" interrupt handling")
Link: https://github.com/ClangBuiltLinux/linux/issues/1151
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 7d86940747d1..0d5ee96f89b4 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -3064,7 +3064,7 @@ static void mvpp2_isr_handle_link(struct mvpp2_port *port, bool link)
 
 static void mvpp2_isr_handle_xlg(struct mvpp2_port *port)
 {
-	bool link;
+	bool link = false;
 	u32 val;
 
 	val = readl(port->base + MVPP22_XLG_INT_STAT);
@@ -3078,7 +3078,7 @@ static void mvpp2_isr_handle_xlg(struct mvpp2_port *port)
 
 static void mvpp2_isr_handle_gmac_internal(struct mvpp2_port *port)
 {
-	bool link;
+	bool link = false;
 	u32 val;
 
 	if (phy_interface_mode_is_rgmii(port->phy_interface) ||

base-commit: 4f6a5caf187ff5807cd5b4ea5678982c249bd964
-- 
2.28.0

Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[David Miller]

From: Nathan Chancellor <natechancellor@gmail.com>
Date: Thu, 10 Sep 2020 10:48:27 -0700

> Clang warns (trimmed for brevity):
> 
> drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3073:7: warning:
> variable 'link' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>                 if (val & MVPP22_XLG_STATUS_LINK_UP)
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3075:31: note:
> uninitialized use occurs here
>                 mvpp2_isr_handle_link(port, link);
>                                             ^~~~
> ...
> drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3090:8: warning:
> variable 'link' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>                         if (val & MVPP2_GMAC_STATUS0_LINK_UP)
>                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3092:32: note:
> uninitialized use occurs here
>                         mvpp2_isr_handle_link(port, link);
>                                                     ^~~~
> 
> Initialize link to false like it was before the refactoring that
> happened around link status so that a valid valid is always passed into
> mvpp2_isr_handle_link.
> 
> Fixes: 36cfd3a6e52b ("net: mvpp2: restructure "link status" interrupt handling")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1151
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

This got fixed via another change, a much mode simply one in fact,
changing the existing assignments to be unconditional and of the
form "link = (bits & MASK);"

Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[Nathan Chancellor]

On Thu, Sep 10, 2020 at 03:28:11PM -0700, David Miller wrote:
> From: Nathan Chancellor <natechancellor@gmail.com>
> Date: Thu, 10 Sep 2020 10:48:27 -0700
> 
> > Clang warns (trimmed for brevity):
> > 
> > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3073:7: warning:
> > variable 'link' is used uninitialized whenever 'if' condition is false
> > [-Wsometimes-uninitialized]
> >                 if (val & MVPP22_XLG_STATUS_LINK_UP)
> >                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3075:31: note:
> > uninitialized use occurs here
> >                 mvpp2_isr_handle_link(port, link);
> >                                             ^~~~
> > ...
> > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3090:8: warning:
> > variable 'link' is used uninitialized whenever 'if' condition is false
> > [-Wsometimes-uninitialized]
> >                         if (val & MVPP2_GMAC_STATUS0_LINK_UP)
> >                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3092:32: note:
> > uninitialized use occurs here
> >                         mvpp2_isr_handle_link(port, link);
> >                                                     ^~~~
> > 
> > Initialize link to false like it was before the refactoring that
> > happened around link status so that a valid valid is always passed into
> > mvpp2_isr_handle_link.
> > 
> > Fixes: 36cfd3a6e52b ("net: mvpp2: restructure "link status" interrupt handling")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1151
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> 
> This got fixed via another change, a much mode simply one in fact,
> changing the existing assignments to be unconditional and of the
> form "link = (bits & MASK);"

Ah great, that is indeed cleaner, thank you for letting me know!

Cheers,
Nathan

Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[Russell King - ARM Linux admin]

On Thu, Sep 10, 2020 at 05:31:42PM -0700, Nathan Chancellor wrote:
> On Thu, Sep 10, 2020 at 03:28:11PM -0700, David Miller wrote:
> > From: Nathan Chancellor <natechancellor@gmail.com>
> > Date: Thu, 10 Sep 2020 10:48:27 -0700
> > 
> > > Clang warns (trimmed for brevity):
> > > 
> > > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3073:7: warning:
> > > variable 'link' is used uninitialized whenever 'if' condition is false
> > > [-Wsometimes-uninitialized]
> > >                 if (val & MVPP22_XLG_STATUS_LINK_UP)
> > >                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3075:31: note:
> > > uninitialized use occurs here
> > >                 mvpp2_isr_handle_link(port, link);
> > >                                             ^~~~
> > > ...
> > > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3090:8: warning:
> > > variable 'link' is used uninitialized whenever 'if' condition is false
> > > [-Wsometimes-uninitialized]
> > >                         if (val & MVPP2_GMAC_STATUS0_LINK_UP)
> > >                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c:3092:32: note:
> > > uninitialized use occurs here
> > >                         mvpp2_isr_handle_link(port, link);
> > >                                                     ^~~~
> > > 
> > > Initialize link to false like it was before the refactoring that
> > > happened around link status so that a valid valid is always passed into
> > > mvpp2_isr_handle_link.
> > > 
> > > Fixes: 36cfd3a6e52b ("net: mvpp2: restructure "link status" interrupt handling")
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/1151
> > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > 
> > This got fixed via another change, a much mode simply one in fact,
> > changing the existing assignments to be unconditional and of the
> > form "link = (bits & MASK);"
> 
> Ah great, that is indeed cleaner, thank you for letting me know!

Hmm, I'm not sure why gcc didn't find that. Strangely, the 0-day bot
seems to have only picked up on it with clang, not gcc.

Thanks for fixing.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[Jakub Kicinski]

On Fri, 11 Sep 2020 12:11:58 +0100 Russell King - ARM Linux admin wrote:
> On Thu, Sep 10, 2020 at 05:31:42PM -0700, Nathan Chancellor wrote:
> > Ah great, that is indeed cleaner, thank you for letting me know!  
> 
> Hmm, I'm not sure why gcc didn't find that. Strangely, the 0-day bot
> seems to have only picked up on it with clang, not gcc.

May be similar to: https://lkml.org/lkml/2019/2/25/1092

Recent GCC is so bad at catching uninitialized vars I was considering
build testing with GCC8 :/

Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[Nathan Chancellor]

On Fri, Sep 11, 2020 at 08:22:36AM -0700, Jakub Kicinski wrote:
> On Fri, 11 Sep 2020 12:11:58 +0100 Russell King - ARM Linux admin wrote:
> > On Thu, Sep 10, 2020 at 05:31:42PM -0700, Nathan Chancellor wrote:
> > > Ah great, that is indeed cleaner, thank you for letting me know!  
> > 
> > Hmm, I'm not sure why gcc didn't find that. Strangely, the 0-day bot
> > seems to have only picked up on it with clang, not gcc.
> 
> May be similar to: https://lkml.org/lkml/2019/2/25/1092
> 
> Recent GCC is so bad at catching uninitialized vars I was considering
> build testing with GCC8 :/

It is even simpler than that, the warning was straight up disabled in
commit 78a5255ffb6a ("Stop the ad-hoc games with -Wno-maybe-initialized").

clang's -Wuninitialized and -Wsometimes-uninitialized are generally more
accurate but can have some false positives because the semantic analysis
phase happens before inlining and dead code elimination.

Cheers,
Nathan

Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac_internal}

[Russell King - ARM Linux admin]

On Fri, Sep 11, 2020 at 09:01:01AM -0700, Nathan Chancellor wrote:
> On Fri, Sep 11, 2020 at 08:22:36AM -0700, Jakub Kicinski wrote:
> > On Fri, 11 Sep 2020 12:11:58 +0100 Russell King - ARM Linux admin wrote:
> > > On Thu, Sep 10, 2020 at 05:31:42PM -0700, Nathan Chancellor wrote:
> > > > Ah great, that is indeed cleaner, thank you for letting me know!  
> > > 
> > > Hmm, I'm not sure why gcc didn't find that. Strangely, the 0-day bot
> > > seems to have only picked up on it with clang, not gcc.
> > 
> > May be similar to: https://lkml.org/lkml/2019/2/25/1092
> > 
> > Recent GCC is so bad at catching uninitialized vars I was considering
> > build testing with GCC8 :/
> 
> It is even simpler than that, the warning was straight up disabled in
> commit 78a5255ffb6a ("Stop the ad-hoc games with -Wno-maybe-initialized").

Great, so now rather than getting false positive warnings, we now
get buggy code. That sounds like a good improvement to me.

Not.

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