[PATCH] ubi: wl: Silence uninitialized variable warning

[PATCH] ubi: wl: Silence uninitialized variable warning

[Dan Carpenter]

This condition needs to be fipped around because "err" is uninitialized
when "force" is set.  The Smatch static analysis tool complains and
UBsan will also complain at runtime.

Fixes: 663586c0a892 ("ubi: Expose the bitrot interface")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/mtd/ubi/wl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 40f838d54b0f..2709dc02fc24 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -1517,7 +1517,7 @@ int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
 		mutex_unlock(&ubi->buf_mutex);
 	}
 
-	if (err == UBI_IO_BITFLIPS || force) {
+	if (force || err == UBI_IO_BITFLIPS) {
 		/*
 		 * Okay, bit flip happened, let's figure out what we can do.
 		 */
-- 
2.17.1


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Re: [PATCH] ubi: wl: Silence uninitialized variable warning

[Richard Weinberger]

Am Donnerstag, 28. Februar 2019, 06:35:51 CET schrieb Dan Carpenter:
> This condition needs to be fipped around because "err" is uninitialized
> when "force" is set.  The Smatch static analysis tool complains and
> UBsan will also complain at runtime.
> 
> Fixes: 663586c0a892 ("ubi: Expose the bitrot interface")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  drivers/mtd/ubi/wl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> index 40f838d54b0f..2709dc02fc24 100644
> --- a/drivers/mtd/ubi/wl.c
> +++ b/drivers/mtd/ubi/wl.c
> @@ -1517,7 +1517,7 @@ int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
>  		mutex_unlock(&ubi->buf_mutex);
>  	}
>  
> -	if (err == UBI_IO_BITFLIPS || force) {
> +	if (force || err == UBI_IO_BITFLIPS) {
>  		/*
>  		 * Okay, bit flip happened, let's figure out what we can do.
>  		 */
> 

Good catch, Dan!
I thought gcc is supposed to find such issues too. :-/

Thanks,
//richard



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Re: [PATCH] ubi: wl: Silence uninitialized variable warning

[Nathan Chancellor]

On Thu, Feb 28, 2019 at 09:35:50AM +0100, Richard Weinberger wrote:
> Am Donnerstag, 28. Februar 2019, 06:35:51 CET schrieb Dan Carpenter:
> > This condition needs to be fipped around because "err" is uninitialized
> > when "force" is set.  The Smatch static analysis tool complains and
> > UBsan will also complain at runtime.
> > 
> > Fixes: 663586c0a892 ("ubi: Expose the bitrot interface")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>

This fixes a -Wsometimes-uninitialized warning from Clang:

drivers/mtd/ubi/wl.c:1514:6: warning: variable 'err' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
        if (!force) {
            ^~~~~~
drivers/mtd/ubi/wl.c:1520:6: note: uninitialized use occurs here
        if (err == UBI_IO_BITFLIPS || force) {
            ^~~
drivers/mtd/ubi/wl.c:1514:2: note: remove the 'if' if its condition is always true
        if (!force) {
        ^~~~~~~~~~~~
drivers/mtd/ubi/wl.c:1478:9: note: initialize the variable 'err' to silence this warning
        int err;
               ^
                = 0
1 warning generated.

> > ---
> >  drivers/mtd/ubi/wl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> > index 40f838d54b0f..2709dc02fc24 100644
> > --- a/drivers/mtd/ubi/wl.c
> > +++ b/drivers/mtd/ubi/wl.c
> > @@ -1517,7 +1517,7 @@ int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
> >  		mutex_unlock(&ubi->buf_mutex);
> >  	}
> >  
> > -	if (err == UBI_IO_BITFLIPS || force) {
> > +	if (force || err == UBI_IO_BITFLIPS) {
> >  		/*
> >  		 * Okay, bit flip happened, let's figure out what we can do.
> >  		 */
> > 
> 
> Good catch, Dan!
> I thought gcc is supposed to find such issues too. :-/

This isn't the first time GCC hasn't caught something...

https://lore.kernel.org/lkml/20190221222123.GC6474@magnolia/

> 
> Thanks,
> //richard
> 
> 

Thanks,
Nathan

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Re: [PATCH] ubi: wl: Silence uninitialized variable warning

[Richard Weinberger]

Am Donnerstag, 28. Februar 2019, 09:50:58 CET schrieb Nathan Chancellor:
> On Thu, Feb 28, 2019 at 09:35:50AM +0100, Richard Weinberger wrote:
> > Am Donnerstag, 28. Februar 2019, 06:35:51 CET schrieb Dan Carpenter:
> > > This condition needs to be fipped around because "err" is uninitialized
> > > when "force" is set.  The Smatch static analysis tool complains and
> > > UBsan will also complain at runtime.
> > > 
> > > Fixes: 663586c0a892 ("ubi: Expose the bitrot interface")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> Tested-by: Nathan Chancellor <natechancellor@gmail.com>

Did you really test the code or just compile it?
 
> This fixes a -Wsometimes-uninitialized warning from Clang:
> 
> drivers/mtd/ubi/wl.c:1514:6: warning: variable 'err' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>         if (!force) {
>             ^~~~~~
> drivers/mtd/ubi/wl.c:1520:6: note: uninitialized use occurs here
>         if (err == UBI_IO_BITFLIPS || force) {
>             ^~~
> drivers/mtd/ubi/wl.c:1514:2: note: remove the 'if' if its condition is always true
>         if (!force) {
>         ^~~~~~~~~~~~
> drivers/mtd/ubi/wl.c:1478:9: note: initialize the variable 'err' to silence this warning
>         int err;
>                ^
>                 = 0
> 1 warning generated.

How much false positives does this trigger?
Many useful gcc warnings are disabled because they produce too much churn.

> > > ---
> > >  drivers/mtd/ubi/wl.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> > > index 40f838d54b0f..2709dc02fc24 100644
> > > --- a/drivers/mtd/ubi/wl.c
> > > +++ b/drivers/mtd/ubi/wl.c
> > > @@ -1517,7 +1517,7 @@ int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
> > >  		mutex_unlock(&ubi->buf_mutex);
> > >  	}
> > >  
> > > -	if (err == UBI_IO_BITFLIPS || force) {
> > > +	if (force || err == UBI_IO_BITFLIPS) {
> > >  		/*
> > >  		 * Okay, bit flip happened, let's figure out what we can do.
> > >  		 */
> > > 
> > 
> > Good catch, Dan!
> > I thought gcc is supposed to find such issues too. :-/
> 
> This isn't the first time GCC hasn't caught something...
> 
> https://lore.kernel.org/lkml/20190221222123.GC6474@magnolia/

Compilers are not perfect. :-)

Thanks,
//richard



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Re: [PATCH] ubi: wl: Silence uninitialized variable warning

[Nathan Chancellor]

On Thu, Feb 28, 2019 at 10:51:12AM +0100, Richard Weinberger wrote:
> Am Donnerstag, 28. Februar 2019, 09:50:58 CET schrieb Nathan Chancellor:
> > On Thu, Feb 28, 2019 at 09:35:50AM +0100, Richard Weinberger wrote:
> > > Am Donnerstag, 28. Februar 2019, 06:35:51 CET schrieb Dan Carpenter:
> > > > This condition needs to be fipped around because "err" is uninitialized
> > > > when "force" is set.  The Smatch static analysis tool complains and
> > > > UBsan will also complain at runtime.
> > > > 
> > > > Fixes: 663586c0a892 ("ubi: Expose the bitrot interface")
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > 
> > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> > Tested-by: Nathan Chancellor <natechancellor@gmail.com>
> 
> Did you really test the code or just compile it?
>  

Compiled tested. If I shouldn't use that tag in that instance, please
let me know.

> > This fixes a -Wsometimes-uninitialized warning from Clang:
> > 
> > drivers/mtd/ubi/wl.c:1514:6: warning: variable 'err' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> >         if (!force) {
> >             ^~~~~~
> > drivers/mtd/ubi/wl.c:1520:6: note: uninitialized use occurs here
> >         if (err == UBI_IO_BITFLIPS || force) {
> >             ^~~
> > drivers/mtd/ubi/wl.c:1514:2: note: remove the 'if' if its condition is always true
> >         if (!force) {
> >         ^~~~~~~~~~~~
> > drivers/mtd/ubi/wl.c:1478:9: note: initialize the variable 'err' to silence this warning
> >         int err;
> >                ^
> >                 = 0
> > 1 warning generated.
> 
> How much false positives does this trigger?
> Many useful gcc warnings are disabled because they produce too much churn.
> 

I haven't gone through them all yet but it doesn't seem to trigger as
often as GCC. I think there are only 22 files with a problem across arm,
arm64, and x86_64 allyesconfig.

> > > > ---
> > > >  drivers/mtd/ubi/wl.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> > > > index 40f838d54b0f..2709dc02fc24 100644
> > > > --- a/drivers/mtd/ubi/wl.c
> > > > +++ b/drivers/mtd/ubi/wl.c
> > > > @@ -1517,7 +1517,7 @@ int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
> > > >  		mutex_unlock(&ubi->buf_mutex);
> > > >  	}
> > > >  
> > > > -	if (err == UBI_IO_BITFLIPS || force) {
> > > > +	if (force || err == UBI_IO_BITFLIPS) {
> > > >  		/*
> > > >  		 * Okay, bit flip happened, let's figure out what we can do.
> > > >  		 */
> > > > 
> > > 
> > > Good catch, Dan!
> > > I thought gcc is supposed to find such issues too. :-/
> > 
> > This isn't the first time GCC hasn't caught something...
> > 
> > https://lore.kernel.org/lkml/20190221222123.GC6474@magnolia/
> 
> Compilers are not perfect. :-)

Would make everyone's life a lot better if they were :)

Nathan

> 
> Thanks,
> //richard
> 
> 

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