* [PATCH] coresight: potential uninitialized variable in probe()
@ 2019-06-13 6:58 Dan Carpenter
2019-06-13 7:49 ` Leo Yan
2019-06-17 19:27 ` Mathieu Poirier
0 siblings, 2 replies; 6+ messages in thread
From: Dan Carpenter @ 2019-06-13 6:58 UTC (permalink / raw)
To: Mathieu Poirier, Leo Yan
Cc: Alexander Shishkin, kernel-janitors, linux-kernel,
linux-arm-kernel, Suzuki K Poulose
The "drvdata->atclk" clock is optional, but if it gets set to an error
pointer then we're accidentally return an uninitialized variable instead
of success.
Fixes: 78e6427b4e7b ("coresight: funnel: Support static funnel")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
drivers/hwtracing/coresight/coresight-funnel.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
index 5867fcb4503b..fa97cb9ab4f9 100644
--- a/drivers/hwtracing/coresight/coresight-funnel.c
+++ b/drivers/hwtracing/coresight/coresight-funnel.c
@@ -244,6 +244,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
}
pm_runtime_put(dev);
+ ret = 0;
out_disable_clk:
if (ret && !IS_ERR_OR_NULL(drvdata->atclk))
--
2.20.1
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] coresight: potential uninitialized variable in probe()
2019-06-13 6:58 [PATCH] coresight: potential uninitialized variable in probe() Dan Carpenter
@ 2019-06-13 7:49 ` Leo Yan
2019-06-13 8:14 ` Dan Carpenter
2019-06-17 19:27 ` Mathieu Poirier
1 sibling, 1 reply; 6+ messages in thread
From: Leo Yan @ 2019-06-13 7:49 UTC (permalink / raw)
To: Dan Carpenter
Cc: Mathieu Poirier, Suzuki K Poulose, Alexander Shishkin,
kernel-janitors, linux-kernel, linux-arm-kernel
Hi Dan,
On Wed, Jun 12, 2019 at 11:58:15PM -0700, Dan Carpenter wrote:
> The "drvdata->atclk" clock is optional, but if it gets set to an error
> pointer then we're accidentally return an uninitialized variable instead
> of success.
You are right, thanks a lot for pointing out.
I'd like to initialize 'ret = 0' at the head of function, so we can
has the same fashion with other CoreSight drivers (e.g. replicator).
static int funnel_probe(struct device *dev, struct resource *res)
{
- int ret;
+ int ret = 0;
If you agree, could you send a new patch for this?
Thanks,
Leo Yan
> Fixes: 78e6427b4e7b ("coresight: funnel: Support static funnel")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> drivers/hwtracing/coresight/coresight-funnel.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
> index 5867fcb4503b..fa97cb9ab4f9 100644
> --- a/drivers/hwtracing/coresight/coresight-funnel.c
> +++ b/drivers/hwtracing/coresight/coresight-funnel.c
> @@ -244,6 +244,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
> }
>
> pm_runtime_put(dev);
> + ret = 0;
>
> out_disable_clk:
> if (ret && !IS_ERR_OR_NULL(drvdata->atclk))
> --
> 2.20.1
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] coresight: potential uninitialized variable in probe()
2019-06-13 7:49 ` Leo Yan
@ 2019-06-13 8:14 ` Dan Carpenter
2019-06-13 9:56 ` Leo Yan
0 siblings, 1 reply; 6+ messages in thread
From: Dan Carpenter @ 2019-06-13 8:14 UTC (permalink / raw)
To: Leo Yan
Cc: Mathieu Poirier, Suzuki K Poulose, Alexander Shishkin,
kernel-janitors, linux-kernel, linux-arm-kernel
On Thu, Jun 13, 2019 at 03:49:22PM +0800, Leo Yan wrote:
> Hi Dan,
>
> On Wed, Jun 12, 2019 at 11:58:15PM -0700, Dan Carpenter wrote:
> > The "drvdata->atclk" clock is optional, but if it gets set to an error
> > pointer then we're accidentally return an uninitialized variable instead
> > of success.
>
> You are right, thanks a lot for pointing out.
>
> I'd like to initialize 'ret = 0' at the head of function, so we can
> has the same fashion with other CoreSight drivers (e.g. replicator).
>
> static int funnel_probe(struct device *dev, struct resource *res)
> {
> - int ret;
> + int ret = 0;
>
> If you agree, could you send a new patch for this?
Obviously that's an option I considered... The reason I didn't go with
that is that a common bug that I see is:
int ret = 0;
p = kmalloc();
if (!p)
goto free_whatever;
In my experience it's better to initialize the return as late as
possible so that you get static checker warnings when you forget to set
the error code.
Also I think my way is more readable. I like to make the success path
as explicit as possible. I hate when people do things like:
if (!ret)
return ret;
About 10% of the time when you see this it is a bug, but it's hard to
tell because it's not readable like it would be if people did:
if (!ret)
return 0;
Or sometimes you see things like:
if (corner_case)
goto free; /* success path */
Without the "/* success path */ comment explaining why we're returning
zero most readers will assume it's a mistake.
regards,
dan carpenter
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] coresight: potential uninitialized variable in probe()
2019-06-13 8:14 ` Dan Carpenter
@ 2019-06-13 9:56 ` Leo Yan
2019-06-13 10:10 ` Leo Yan
0 siblings, 1 reply; 6+ messages in thread
From: Leo Yan @ 2019-06-13 9:56 UTC (permalink / raw)
To: Dan Carpenter
Cc: Mathieu Poirier, Suzuki K Poulose, Alexander Shishkin,
kernel-janitors, linux-kernel, linux-arm-kernel
Hi Dan,
On Thu, Jun 13, 2019 at 11:14:19AM +0300, Dan Carpenter wrote:
> On Thu, Jun 13, 2019 at 03:49:22PM +0800, Leo Yan wrote:
> > Hi Dan,
> >
> > On Wed, Jun 12, 2019 at 11:58:15PM -0700, Dan Carpenter wrote:
> > > The "drvdata->atclk" clock is optional, but if it gets set to an error
> > > pointer then we're accidentally return an uninitialized variable instead
> > > of success.
> >
> > You are right, thanks a lot for pointing out.
> >
> > I'd like to initialize 'ret = 0' at the head of function, so we can
> > has the same fashion with other CoreSight drivers (e.g. replicator).
> >
> > static int funnel_probe(struct device *dev, struct resource *res)
> > {
> > - int ret;
> > + int ret = 0;
> >
> > If you agree, could you send a new patch for this?
>
> Obviously that's an option I considered... The reason I didn't go with
> that is that a common bug that I see is:
>
> int ret = 0;
>
> p = kmalloc();
> if (!p)
> goto free_whatever;
>
> In my experience it's better to initialize the return as late as
> possible so that you get static checker warnings when you forget to set
> the error code.
Just want to check one thing, which static checker you are using?
I use sparse but it doesn't report this issue (I learned coccinelle
also can do this but it outputs verbose logs).
To be honest, I didn't often run static checker when committed patches,
but hope later can improve for this.
> Also I think my way is more readable. I like to make the success path
> as explicit as possible. I hate when people do things like:
>
> if (!ret)
> return ret;
>
> About 10% of the time when you see this it is a bug, but it's hard to
> tell because it's not readable like it would be if people did:
>
> if (!ret)
> return 0;
>
> Or sometimes you see things like:
>
> if (corner_case)
> goto free; /* success path */
>
> Without the "/* success path */ comment explaining why we're returning
> zero most readers will assume it's a mistake.
Thanks for sharing much knowledge; your change is okay for me.
I think the point is the good habit can avoid pitfall and traps :) [1]
Thanks,
Leo Yan
[1] https://www.amazon.com/C-Traps-Pitfalls-Andrew-Koenig/dp/0201179288
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] coresight: potential uninitialized variable in probe()
2019-06-13 9:56 ` Leo Yan
@ 2019-06-13 10:10 ` Leo Yan
0 siblings, 0 replies; 6+ messages in thread
From: Leo Yan @ 2019-06-13 10:10 UTC (permalink / raw)
To: Dan Carpenter
Cc: Mathieu Poirier, Suzuki K Poulose, Alexander Shishkin,
kernel-janitors, linux-kernel, linux-arm-kernel
On Thu, Jun 13, 2019 at 05:56:37PM +0800, Leo Yan wrote:
[...]
> > In my experience it's better to initialize the return as late as
> > possible so that you get static checker warnings when you forget to set
> > the error code.
>
> Just want to check one thing, which static checker you are using?
Okay, I think it's smatch :)
Thanks,
Leo Yan
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] coresight: potential uninitialized variable in probe()
2019-06-13 6:58 [PATCH] coresight: potential uninitialized variable in probe() Dan Carpenter
2019-06-13 7:49 ` Leo Yan
@ 2019-06-17 19:27 ` Mathieu Poirier
1 sibling, 0 replies; 6+ messages in thread
From: Mathieu Poirier @ 2019-06-17 19:27 UTC (permalink / raw)
To: Dan Carpenter
Cc: Suzuki K Poulose, Alexander Shishkin, kernel-janitors,
Linux Kernel Mailing List, Leo Yan, linux-arm-kernel
On Thu, 13 Jun 2019 at 00:59, Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> The "drvdata->atclk" clock is optional, but if it gets set to an error
> pointer then we're accidentally return an uninitialized variable instead
> of success.
>
> Fixes: 78e6427b4e7b ("coresight: funnel: Support static funnel")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> drivers/hwtracing/coresight/coresight-funnel.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
> index 5867fcb4503b..fa97cb9ab4f9 100644
> --- a/drivers/hwtracing/coresight/coresight-funnel.c
> +++ b/drivers/hwtracing/coresight/coresight-funnel.c
> @@ -244,6 +244,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
> }
>
> pm_runtime_put(dev);
> + ret = 0;
Applied - thanks.
>
> out_disable_clk:
> if (ret && !IS_ERR_OR_NULL(drvdata->atclk))
> --
> 2.20.1
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-06-17 19:27 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-06-13 6:58 [PATCH] coresight: potential uninitialized variable in probe() Dan Carpenter
2019-06-13 7:49 ` Leo Yan
2019-06-13 8:14 ` Dan Carpenter
2019-06-13 9:56 ` Leo Yan
2019-06-13 10:10 ` Leo Yan
2019-06-17 19:27 ` Mathieu Poirier
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).