netdev - Re: [PATCH wireless-next] wifi: mac80211: fix use-after-free risk in sta debugfs removal

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Message-ID: <b81013d8f7cccb19ab126aebc7bc442c641d0f4a.camel@sipsolutions.net>
Date: Thu, 24 Jul 2025 09:18:07 +0200
From: Johannes Berg <johannes@...solutions.net>
To: Moon Hee Lee <moonhee.lee.ca@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org, 
	linux-kernel-mentees@...ts.linux.dev, netdev@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, 
	syzbot+d6ccd49ae046542a0641@...kaller.appspotmail.com, 
	skhan@...uxfoundation.org, david.hunter.linux@...il.com
Subject: Re: [PATCH wireless-next] wifi: mac80211: fix use-after-free risk
 in sta debugfs removal

On Thu, 2025-07-24 at 00:15 -0700, Moon Hee Lee wrote:
> A NULL pointer dereference may occur in ieee80211_sta_debugfs_remove()
> when debugfs_remove_recursive() is called on a dentry whose inode has
> already been freed. This can happen due to a race between STA teardown
> and debugfs cleanup.
> 
> Fix this by checking that both sta->debugfs_dir and its d_inode are
> valid before invoking debugfs_remove_recursive().
> 
> This avoids the crash reported in syzbot bug:

Maybe so, but it really looks like a bandaid?! Why are we trying to
remove it twice in the first place?

johannes