linux-kernel - [PATCH 5.6 140/177] cfg80211: fix debugfs rename crash

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Message-Id: <20200601174100.213877366@linuxfoundation.org>
Date:   Mon,  1 Jun 2020 19:54:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+fd5332e429401bf42d18@...kaller.appspotmail.com,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 5.6 140/177] cfg80211: fix debugfs rename crash

From: Johannes Berg <johannes.berg@...el.com>

commit 0bbab5f0301587cad4e923ccc49bb910db86162c upstream.

Removing the "if (IS_ERR(dir)) dir = NULL;" check only works
if we adjust the remaining code to not rely on it being NULL.
Check IS_ERR_OR_NULL() before attempting to dereference it.

I'm not actually entirely sure this fixes the syzbot crash as
the kernel config indicates that they do have DEBUG_FS in the
kernel, but this is what I found when looking there.

Cc: stable@...r.kernel.org
Fixes: d82574a8e5a4 ("cfg80211: no need to check return value of debugfs_create functions")
Reported-by: syzbot+fd5332e429401bf42d18@...kaller.appspotmail.com
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Link: https://lore.kernel.org/r/20200525113816.fc4da3ec3d4b.Ica63a110679819eaa9fb3bc1b7437d96b1fd187d@changeid
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/wireless/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -142,7 +142,7 @@ int cfg80211_dev_rename(struct cfg80211_
 	if (result)
 		return result;
 
-	if (rdev->wiphy.debugfsdir)
+	if (!IS_ERR_OR_NULL(rdev->wiphy.debugfsdir))
 		debugfs_rename(rdev->wiphy.debugfsdir->d_parent,
 			       rdev->wiphy.debugfsdir,
 			       rdev->wiphy.debugfsdir->d_parent, newname);