[PATCH] net: mac80211: use IS_ERR to check return value

[PATCH] net: mac80211: use IS_ERR to check return value

[yingsha xu]

According to the annotation of function debugfs_create_fs, if
an error occurs, ERR_PTR(-ERROR) will be returned instead of
a null pointer or zero value.

Fix it by using IS_ERR().

Fixes: e9f207f0ff90 ("[MAC80211]: Add debugfs attributes.")
Signed-off-by: yingsha xu <ysxu@hust.edu.cn>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
---
 net/mac80211/debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index dfb9f55e2685..672bf969ad88 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -674,7 +674,7 @@ void debugfs_hw_add(struct ieee80211_local *local)
 	statsd = debugfs_create_dir("statistics", phyd);
 
 	/* if the dir failed, don't put all the other things into the root! */
-	if (!statsd)
+	if (IS_ERR(statsd))
 		return;
 
 #ifdef CONFIG_MAC80211_DEBUG_COUNTERS
-- 
2.17.1

Re: [PATCH] net: mac80211: use IS_ERR to check return value

[Johannes Berg]

On Sun, 2023-04-16 at 16:30 +0800, yingsha xu wrote:
> According to the annotation of function debugfs_create_fs, if
> an error occurs, ERR_PTR(-ERROR) will be returned instead of
> a null pointer or zero value.
> 
> Fix it by using IS_ERR().

I don't this this is right, or fixed anything ...

If debugfs indeed returned an ERR_PTR() value, then the later debugfs
adds will do nothing.

Since it doesn't look like debugfs_create_dir() can actually return NULL
these days (not sure it ever could), I guess we can even remove the
check.

But you could've just read the comment there too, to know what the NULL
check was about ...

johannes

Re: [PATCH] net: mac80211: use IS_ERR to check return value

[Dan Carpenter]

On Tue, Apr 18, 2023 at 10:36:14AM +0200, Johannes Berg wrote:
> On Sun, 2023-04-16 at 16:30 +0800, yingsha xu wrote:
> > According to the annotation of function debugfs_create_fs, if
> > an error occurs, ERR_PTR(-ERROR) will be returned instead of
> > a null pointer or zero value.
> > 
> > Fix it by using IS_ERR().
> 
> I don't this this is right, or fixed anything ...
> 
> If debugfs indeed returned an ERR_PTR() value, then the later debugfs
> adds will do nothing.
> 
> Since it doesn't look like debugfs_create_dir() can actually return NULL
> these days (not sure it ever could), I guess we can even remove the
> check.
> 

Correct.  They have a patch ready which deletes the check and the
comment.  Someone should have replied to this thread to NAK their own
patch so that you didn't bother reviewing it.

> But you could've just read the comment there too, to know what the NULL
> check was about ...

The comment was always wrong.  Debugfs could return NULL but then
the other debugfs functions turned into no ops...

regards,
dan carpenter