[PATCH] drivers/acpi/ec.c fix a small memory leak

[PATCH] drivers/acpi/ec.c fix a small memory leak

[Darren Jenkins]

Plug a very small leak in acpi_ec_ecdt_probe()

Coverity CID: 13319

Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com> 

diff --git drivers/acpi/ec.c drivers/acpi/ec.c
index d6471bb..13061dc 100644
--- drivers/acpi/ec.c
+++ drivers/acpi/ec.c
@@ -1009,8 +1009,10 @@ int __init acpi_ec_ecdt_probe(void)
 	/* fall through */
 	}
 
-	if (EC_FLAGS_SKIP_DSDT_SCAN)
+	if (EC_FLAGS_SKIP_DSDT_SCAN) {
+		kfree(saved_ec);
 		return -ENODEV;
+	}
 
 	/* This workaround is needed only on some broken machines,
 	 * which require early EC, but fail to provide ECDT */

Re: [PATCH] drivers/acpi/ec.c fix a small memory leak

[Alexey Starikovskiy]

NAK

saved_ec is allocated if flag EC_FLAGS_VALIDATE_ECDT is true.
EC_FLAGS_SKIP_DSDT_SCAN have no sense in such case, thus this new code path
is never executed.
On the other hand, unconditionally freeing pointer, which is might be NULL, is not
right either.
So, this patch introduced more problems as it tries to solve...

Regards,
Alex.

Darren Jenkins пишет:
> Plug a very small leak in acpi_ec_ecdt_probe()
> 
> Coverity CID: 13319
> 
> Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com> 
> 
> diff --git drivers/acpi/ec.c drivers/acpi/ec.c
> index d6471bb..13061dc 100644
> --- drivers/acpi/ec.c
> +++ drivers/acpi/ec.c
> @@ -1009,8 +1009,10 @@ int __init acpi_ec_ecdt_probe(void)
>  	/* fall through */
>  	}
>  
> -	if (EC_FLAGS_SKIP_DSDT_SCAN)
> +	if (EC_FLAGS_SKIP_DSDT_SCAN) {
> +		kfree(saved_ec);
>  		return -ENODEV;
> +	}
>  
>  	/* This workaround is needed only on some broken machines,
>  	 * which require early EC, but fail to provide ECDT */
> 
> 

Re: [PATCH] drivers/acpi/ec.c fix a small memory leak

[Dan Carpenter]

On Tue, Feb 02, 2010 at 06:35:44PM +0300, Alexey Starikovskiy wrote:
> NAK
> 
> saved_ec is allocated if flag EC_FLAGS_VALIDATE_ECDT is true.
> EC_FLAGS_SKIP_DSDT_SCAN have no sense in such case, thus this new code path
> is never executed.
> On the other hand, unconditionally freeing pointer, which is might be NULL, is not
> right either.

As near as I can tell you are right that the code cannot leak memory.  But Darren 
is right to think that it's calling kfree() on a NULL pointer is OK.  His patch does 
not introduce any errors.

The logic here is basically spaghetti.  Every person who looks at it is going to 
think it's a leak.  Lots of people are going to look at it, because the static
checkers all think it's a leak too.  Someone could send a cleanup patch that makes it
readable.

regards,
dan carpenter

> So, this patch introduced more problems as it tries to solve...
> 
> Regards,
> Alex.
> 
> Darren Jenkins пишет:
> > Plug a very small leak in acpi_ec_ecdt_probe()
> > 
> > Coverity CID: 13319
> > 
> > Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com> 
> > 
> > diff --git drivers/acpi/ec.c drivers/acpi/ec.c
> > index d6471bb..13061dc 100644
> > --- drivers/acpi/ec.c
> > +++ drivers/acpi/ec.c
> > @@ -1009,8 +1009,10 @@ int __init acpi_ec_ecdt_probe(void)
> >  	/* fall through */
> >  	}
> >  
> > -	if (EC_FLAGS_SKIP_DSDT_SCAN)
> > +	if (EC_FLAGS_SKIP_DSDT_SCAN) {
> > +		kfree(saved_ec);
> >  		return -ENODEV;
> > +	}
> >  
> >  	/* This workaround is needed only on some broken machines,
> >  	 * which require early EC, but fail to provide ECDT */
> > 
> > 
> 
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Re: [PATCH] drivers/acpi/ec.c fix a small memory leak

[Bernd Petrovitsch]

On Die, 2010-02-02 at 18:35 +0300, Alexey Starikovskiy wrote:
> NAK
> 
> saved_ec is allocated if flag EC_FLAGS_VALIDATE_ECDT is true.
> EC_FLAGS_SKIP_DSDT_SCAN have no sense in such case, thus this new code path
> is never executed.
> On the other hand, unconditionally freeing pointer, which is might be NULL, is not
> right either.
Why that?
"kfree(NULL);" works (and in the user-space "free(NULL)" too FWIW).

> So, this patch introduced more problems as it tries to solve...

	Bernd
-- 
Bernd Petrovitsch                  Email : bernd@petrovitsch.priv.at
                     LUGA : http://www.luga.at

Re: [PATCH] drivers/acpi/ec.c fix a small memory leak

[Darren Jenkins]

Hello Alexey,

On Wed, Feb 3, 2010 at 2:35 AM, Alexey Starikovskiy
<astarikovskiy@suse.de> wrote:
> NAK
>
> saved_ec is allocated if flag EC_FLAGS_VALIDATE_ECDT is true.
> EC_FLAGS_SKIP_DSDT_SCAN have no sense in such case, thus this new code path
> is never executed.

>From what I can tell this is not guaranteed by the code, it is relying
on DMI data not matching two of the stings at once.
However I don't know anything about DMI, so if you say this makes no
sense and will never happen I am happy.

I will mark this as ignore in the Coverity databse.

> On the other hand, unconditionally freeing pointer, which is might be NULL, is not
> right either.

Nowadays this is the preferred method actually.

> Regards,
> Alex.

Thanks for the feedback.

Darren J